Next Article in Journal
NOD2 Supports Crypt Survival and Epithelial Regeneration after Radiation-Induced Injury
Next Article in Special Issue
Chromosome Translocations as a Driver of Diversification in Mole Voles Ellobius (Rodentia, Mammalia)
Previous Article in Journal
The Role of Extracellular Matrix Expression, ERK1/2 Signaling and Cell Cohesiveness for Cartilage Yield from iPSCs
Previous Article in Special Issue
Karyotypes and Sex Chromosomes in Two Australian Native Freshwater Fishes, Golden Perch (Macquaria ambigua) and Murray Cod (Maccullochella peelii) (Percichthyidae)
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:

Deciphering the Evolutionary History of Arowana Fishes (Teleostei, Osteoglossiformes, Osteoglossidae): Insight from Comparative Cytogenomics

Departamento de Genética e Evolução, Universidade Federal de São Carlos (UFSCar), São Carlos, SP 13565-090, Brazil
Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, 27721 Liběchov, Czech Republic
Institute for Applied Ecology, University of Canberra, Canberra, ACT 2617, Australia
School of Biological Sciences, Universiti Sains Malaysia, Penang 11800, Malaysia
Secretaria de Estado de Educação de Mato Grosso – SEDUC-MT, Cuiabá, MT 78049-909, Brazil
Departamento de Biologia Celular e Genética, Centro de Biociências, Universidade Federal do Rio Grande do Norte, Natal, RN 59078-970, Brazil
Institute of Human Genetics, University Hospital Jena, 07747 Jena, Germany
Instituto Nacional de Pesquisas da Amazônia, Coordenação de Biodiversidade, Laboratório de Genética Animal, Petrópolis, Manaus, AM 69077-000, Brazil
Toxic Substances in Livestock and Aquatic Animals Research Group, KhonKaen University, Muang, KhonKaen 40002, Thailand
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2019, 20(17), 4296;
Received: 13 August 2019 / Revised: 30 August 2019 / Accepted: 30 August 2019 / Published: 2 September 2019
(This article belongs to the Special Issue Chromosome and Karyotype Variation)


Arowanas (Osteoglossinae) are charismatic freshwater fishes with six species and two genera (Osteoglossum and Scleropages) distributed in South America, Asia, and Australia. In an attempt to provide a better assessment of the processes shaping their evolution, we employed a set of cytogenetic and genomic approaches, including i) molecular cytogenetic analyses using C- and CMA3/DAPI staining, repetitive DNA mapping, comparative genomic hybridization (CGH), and Zoo-FISH, along with ii) the genotypic analyses of single nucleotide polymorphisms (SNPs) generated by diversity array technology sequencing (DArTseq). We observed diploid chromosome numbers of 2n = 56 and 54 in O. bicirrhosum and O. ferreirai, respectively, and 2n = 50 in S. formosus, while S. jardinii and S. leichardti presented 2n = 48 and 44, respectively. A time-calibrated phylogenetic tree revealed that Osteoglossum and Scleropages divergence occurred approximately 50 million years ago (MYA), at the time of the final separation of Australia and South America (with Antarctica). Asian S. formosus and Australian Scleropages diverged about 35.5 MYA, substantially after the latest terrestrial connection between Australia and Southeast Asia through the Indian plate movement. Our combined data provided a comprehensive perspective of the cytogenomic diversity and evolution of arowana species on a timescale.

1. Introduction

The fish superorder Osteoglossomorpha is one of the three main teleostean lineages, along with Elopomorpha and Clupeocephala [1,2,3,4]. Osteoglossomorpha is divided into two orders, the relictual Hiodontiformes (comprising only two North American extant species of Hiodon) and the Osteoglossiformes, which currently comprises 244 valid species (restricted to freshwater tropical regions), classified into five families, namely Pantodontidae, Notopteridae, Gymnarchidae, Mormyridae, and Osteoglossidae [5,6,7]. The distribution of Osteoglossiformes is predominantly Gondwanic, with representatives occurring in Africa (center of diversity), South America, and Sahul (i.e., Australia and New Guinea) [6,7]. Such trans-oceanic distribution, combined with ancient age and distinct phylogenetic position, make Osteoglossiformes a unique model to understand the evolution and biogeography of freshwater fishes [1,6,8,9]. In this study, we focused on the subfamily Osteoglossinae of the family Osteoglossidae.
The Osteoglossidae is divided into two reciprocally monophyletic subfamilies (Osteoglossinae and Arapaiminae [= Heterotidinae]), each of them comprising two genera. The subfamily Osteoglossinae, commonly known as arowanas, includes Osteoglossum and Scleropages [5]. Osteoglossum is endemic to Amazonian floodplains and it currently consists of the silver arowana, O. bicirrhosum (Cuvier, 1829), and the black arowana, O. ferreirai (Kanazawa, 1966). In Southeast Asia, Scleropages includes two valid species [7,10], the Asian arowana S. formosus (Müller and Schlegel 1840) and the Batik arowana S. inscriptus [11]. As some allopatric populations of S. formosus exhibit differences in body coloration, it was thought for a long time that they might represent distinct species [12], which were formally described by Pouyaud et al. [13]. However, Kottelat and Widjanarti [14] reexamined the data from Pouyaud et al. [13] and found that they do not support the authors’ conclusions, suggesting that natural color variants were merely allopatric populations of a single species, S. formosus [6,7,10]. The remaining important taxonomic question is to determine whether S. inscriptus, which is known only from its holotype and paratype, is valid relative to S. formosus.
In Sahul, Scleropages includes two extant species: the southern saratoga, S. leichardti (Günther, 1864) endemic to the Fitzroy River system in Queensland (Figure 1), and the northern saratoga, S. jardinii (Saville–Kent, 1892), which inhabits three separate areas in northern Australia and central-southern New Guinea.
Previous molecular phylogenetic studies of osteoglossids were based on mitochondrial, and few nuclear markers [6,15,16,17]. These studies indicated that Osteoglossum and Scleropages were sister groups and that the same also applied for the relationship between S. formosus and Australian Scleropages. It should be noted that the monophyly of Scleropages has not yet been corroborated by convincing morphological evidence [18]. Whereas the molecular phylogeny of arowana seems well resolved, where several recent studies raised potential artifacts of using only one or few markers, resulting in highly supported but unreliable inferences [19,20,21]. High throughput sequencing technology (NGS) and genotyping by sequencing methods have the power to overcome the limitations of obtaining large datasets from non-model species that include genetic information from thousands of genomic regions [22,23,24]. Among the strategies available for obtaining polymorphic markers, DArTseq (diversity array technology sequencing) has increasingly been used for phylogeographic and phylogenetic purposes [25,26,27,28,29].
The extant arowana species have a discontinuous geographic distribution across South America, Southeast Asia, and Sahul (Figure 1). The causes of such disjunct distributions are still unclear, with two opposing hypotheses being debated (for a comprehensive review, see Reference [6]). Some authors assert that the biogeography of Osteoglossinae was driven by the tectonic-mediated Gondwanan fragmentation (such as the fragmentation of South America–Antarctica–Australia and/or the fragmentation of India–Australia) [8,30,31]; whereas others suggest that a post-fragmentation transmarine dispersal accounted for the observed pattern [32]. Recently published molecular dating studies tend to support a scenario in which both vicariance and marine dispersal events played a role in the distribution of these fishes [16,17]. The fossil record lends support to the marine dispersal hypothesis because it contains a fossil assigned to Scleropages, found in Cenozoic marine deposits [33]. Therefore, additional research is needed to test the outlined biogeographical hypotheses on the intercontinental distribution patterns of these freshwater fishes.
Modern cytogenetic and genomic tools are central to inferring the evolutionary history of ancient fish lineages (e.g., References [3,34,35,36,37,38]). Such data, however, are still scarce for Osteoglossiformes, with Osteoglossidae being a typical example, thereby limiting our understanding of their genome and karyotype evolution ([39]; reviewed in References [35,40,41,42,43]).
Until now, the cytogenetic investigations of arowana species are limited to analyses of conventionally Giemsa-stained chromosomes, usually leading to inconsistent results. For example, Urushido et al. [44] first examined the karyotype of S. formosus and determined its diploid chromosome number as 2n = 50, while subsequent cytogenetic studies inferred 2n = 48 with a karyotype composed of 18 submetacentric (sm) and 30 acrocentric (a) chromosomes [40,45,46]. Karyotypes of S. jardinii and S. leichardti, were reported to have 2n = 48 and 2n = 44, respectively [47]. Suzuki et al. [48] described 2n = 54 in O. ferreirai (6 metacentric (m)-sm + 48a chromosomes), whereas its sister species, O. bicirrhosum, possessed a karyotype with 2n = 56 and 4 subtelocentric (st) + 52a chromosomes [44,48]. In a recent study by Bian et al. [40], which was partially based on molecular cytogenetic approaches, such as fluorescence in situ hybridization (FISH)-based mapping of 5S and 18S rDNA sites on chromosomes of S. formosus, the presence of a ZW sex chromosome system was supposed.
In an attempt to provide a more complex insight into the processes shaping the evolution of arowana species, we employed a set of (molecular) cytogenetic and genomic approaches. More specifically, we applied C- and CMA3/DAPI staining, repetitive DNA mapping via FISH, along with interspecific comparative genomic hybridization (CGH) and Zoo-FISH (i.e., cross-species whole chromosome paintings; WCP) experiments. Time-calibrated phylogenetic reconstructions and genetic divergence were also assessed by DArTseq and were used to discuss their evolution and biogeography. Therefore, our combined dataset allowed us to provide a comprehensive perspective of the cytogenomic diversity and evolution of the arowana species on a phylogenetic and timescale context.

2. Results

2.1. DArTseq Genotyping and Genetic Relationships

DArTseq library preparation and sequencing resulted in 1891 high-quality filtered single nucleotide polymorphism (SNP) markers. After removing extra SNPs in reads with multiple markers, the remaining dataset contained 1565 SNPs (Supplementary Table S1). The principal coordinate analysis (PCoA) recovered 58.8% of the total variation in the first principal component (PC1), and 26.4% in the second (PC2). The analysis was able to clearly separate all arowana species located in separate continents, splitting the two analyzed genera in PC1. PC2 was able to separate the Asian and Australian Scleropages (Figure 2).
The species tree recovered in SVDquartets, rooted with Arapaima gigas and Heterotis niloticus, showed that Osteoglossum and Scleropages were reciprocally monophyletic. Within Scleropages, S. formosus is the sister group of Australian Scleropages. Bootstrap support was higher than 85% for all nodes. The script used to filter the dataset for the SNAPP analysis removed 789 monomorphic SNPs and 639 that contained missing data, resulting in a file with 463 SNPs. The species tree in SNAPP showed the same topology obtained in the SVD quartets, with all posterior probabilities equal to 1 (Figure 1). The divergence time between Arapaiminae (= Heterotidinae) and Osteoglossinae was estimated to 108.7 MYA (86.3–131.2 95% highest posterior density (HPD)). The divergence time between Osteoglossum and Scleropages was estimated to 50.3 MYA (47.8–55.0 95% HPD), in the Early Paleogene. The divergence time between S. formosus and Australian Scleropages was estimated to 35.5 MYA, in the Middle Eocene (27.4–44.3 95% HPD). The age of the crown group Australian Scleropages was estimated in the Neogene, 9.3 MYA (4.9–14.9 95% HPD), while the age of the crown group Osteoglossum was estimated to 6.1 MYA (2.7–9.8 95%HPD). All effective sample size (ESS) values were greater than 1000.

2.2. Karyotypes and C-Banding

Studied species differed among each other by their 2n. In our sampling, we did not observe any karyotype differences between males and females. Both South American arowanas displayed the highest 2n found among arowanas to date. While O. bicirrhosum exhibited 2n = 56, with karyotype being composed only of st-a chromosomes, O. ferreirai possessed 2n = 54, with almost all chromosomes being acrocentric, except for a large metacentric chromosome pair indicative of previous fusion events. S. formosus had 2n = 50 (8sm/m + 42st/a), and a remarkable size polymorphism was observed in the 18th pair (Figure 3E, F boxed) due to the presence of large rDNA sites (see below). The two Australian arowanas S. jardinii and S. leichardti had 2n = 48 and 44, respectively, and karyotypes were dominated by a high proportion of m-sm chromosomes (Figure 3J, H). Constitutive heterochromatin visualized as C-bands were present in the centromeric regions of chromosomes in the karyotypes of all species. Moreover, conspicuous C-positive blocks were observed in pair number 1 of O. ferreirai and O. bicirrhosum, and in mentioned pair number 18 of S. formosus (Figure 3).

2.3. FISH Mapping and CMA3 Banding

The 18S rDNA sites were located in the centromeric region of a single acrocentric pair in all species examined, except for O. ferreirai, which contained four 18S rDNA sites. A remarkable size polymorphism was observed in the 18th pair of male and females of S. formosus due to the copy number variation of DNA cistrons (Figure 4E, boxed).
The 5S rDNA sequences were located on the p arms of acrocentric chromosome pairs, where two sites (S. jardinii), four sites (O. ferreirai, S. leichardti); six sites (S. formosus), eight sites (O. bicirrhosum) were observed (Figure 4). In S. formosus, 5S rDNA regions were found adjacent to the 18S rDNA region on the 18th pair.
CMA3+ bands, which represent GC-rich regions, co-localized exclusively with 18S rDNA sites in both South American arowana species. In contrast, CMA3/DAPI staining of chromosomes of both Australian arowana, S. jardinii and S. leichardti, produced—besides highlighting the 18S rDNA sites—a clear CMA3+ banding pattern along the entire portion of all chromosomes, alternating with a DAPI+ pattern (AT-rich regions), thereby providing clear evidence of genome compartmentalization (Figure 4). FISH with the vertebrate telomeric (TTAGGG)n motif applied on the arowanas with lower 2n, and thus, with an indicative of the occurrence of centric fusions, revealed that hybridization signals on each telomere of all chromosomes and interstitial telomeric sites (ITS) were not detected in the chromosomes of both Australian species (Supplementary Figure S1: Metaphase plates of both Australian arowanas).

2.4. Comparative Genomic Hybridization

In each experiment, genome-derived probes prepared from S. leichardti and one of the compared species showed a rather equal binding to all chromosomes of S. leichardti. There was preferential localization in the centromeric and pericentromeric regions of most chromosomes and in the terminal parts of some of them (yellow signals, i.e., combination of green and red), indicating the shared repetitive content in such regions. The hybridization patterns produced by the genomic DNAs (gDNAs) of the other two Scleropages species (S. jardinii and S. formosus) against the S. leichardti chromosomal background, displayed stronger equal binding of both probes to the centromeric or telomeric regions of several chromosomes. In the cross-genera hybridization, the gDNA probes of both Osteoglossum species produced only a limited number of overlapping signals. More specifically, the S. leichardti gDNA probe hybridizing back against its own chromosome complements highlighted many heterochromatic blocks abundantly present in the centromeric and terminal chromosomal regions. Meanwhile, the probes derived from the gDNA of both Osteoglossum species produced only weak hybridization patterns, with few consistent signals accumulated in the terminal portions of some chromosomes and corresponding to major rDNA sites (Figure 5). The CGH experiments using gDNAs from S. formosus individuals carrying the conspicuous heterochromatic block in one or in both homologs of chromosomal pair number 18, demonstrated that both individuals shared the genome content and that the heterochromatic block was not accumulated with unique classes of repetitive DNA (Supplementary Figure S2: CGH on metaphase of S. formosus).

2.5. Whole Chromosome Painting of the OFE-1 Probe

When applied against metaphase chromosomes of O. ferreirai, the OFE-1 probe completely painted the first chromosome pair, with prominent hybridization signals in both centromeric regions (Figure 6A). The hybridization to other Osteoglossinae species showed that the OFE-1 probe consistently painted two (O. bicirrhosum and S. jardinii) or three (S. formosus and S. leichardti) chromosomal pairs (Figure 6). The SFO-1 probe when applied against metaphase chromosomes of S. formosus completely painted an acrocentric chromosome pair in individuals carrying the conspicuous heterochromatic block in both (Figure 6, C1) or just one (Figure 6, C2) of the homologs. The hybridization in the other Osteoglossidae species showed that the SFO-A probe consistently painted a small acrocentric chromosomal pair (Figure 6). Moreover, as this acrocentric pair in S. formosus presented a conspicuous 18S rDNA site, additional hybridization blocks on the NOR region of some species were also observed (Figure 6).

3. Discussion

3.1. Cytogenetic Differentiation of Osteoglossum and Scleropages

Unsurprisingly, the karyotypes of Osteoglossum and Scleropages species revealed substantial macrostructural rearrangements after 50 MYA of evolutionary divergence. Higher 2n and karyotypes formed by acrocentric chromosomes were found in both Osteoglossum species compared to those of Scleropages, which possessed lower 2n and a higher number of bi-armed chromosomes. Within Scleropages, S. formosus had an intermediate pattern with 2n = 50 and fewer bi-armed chromosomes in the karyotype (Figure 3). While the majority of osteoglossiform species tend to maintain the karyotypes dominated by acrocentric chromosomes, both Australian arowanas and some other osteoglossiforms such as Gymnarchus niloticus (Gymnarchidae) and Gnathonemus petersii (Mormyridae) presented exceptions to this general rule ([35,39,41]; present study). The single fusion event decreasing 2n from 56 in O. bicirrhosum to 54 in O. ferreirai separated the karyotypes of the Osteoglossum species as demonstrated by Zoo-FISH. The karyotype divergence in Scleropages agrees with the phylogenetic hypothesis, indicating that centric fusions operated as an underlying mechanism shaping the karyotype structure, associated with reduced 2n, in both Australian arowanas S. leichardti and S. jardinii. Moreover, CMA3/DAPI staining revealed that the genomes of Australian species were demonstrably compartmentalized, similarly to those of mammals. To date, genomes compartmentalized as a mosaic of AT- and GC-rich isochores have been reported only in genera of non-teleostean gars, Atractosteus and Lepisosteus, but they were believed to be completely absent in the teleostean lineage [36]. Thus, our study brings the first evidence for such genome organization in teleosts, namely in Southeast Asian and Australian arowanas. On the other hand, South American and Southeast Asian arowanas, as a by-product of their evolutionary divergence, do not show such CMA3/DAPI staining patterns. Osteoglossum species show rDNA sites as the only GC-rich regions in the chromosomes, with the rest of the genome being stained homogeneously, indicating a balanced proportion of AT/GC composition (Figure 4). This pattern represents the most common scenario observed in extant fishes, in contrast to the one found in mammals and birds, which present a genomic GC compositional heterogeneity (reviewed in Symonová et al. [36]). Our CGH experiments compared the genomes of all arowana species, indicating that the early separation (50 MYA) produced an advanced stage of sequence divergence between S. leichardti and both Osteoglossum species, except for the NOR sites. The decrease of shared sequences as detected by CGH or related methods was expected for distantly related species and/or substantially diverged genomes [49,50,51], as also demonstrated by NGS technology using DArTseq markers (Figure 2).
Included in the genetic divergence, the higher level of inter-chromosomal rearrangements of arowana genomes [40], herein visualized by CGH and Zoo-FISH, certainly contributed to the deterioration of karyotype/genome homogeneity between the two osteoglossid genera. Numerous structural rearrangements seem to be the predominant types of chromosomal changes among distant and close phylogenetic clades of arowanas, and they seem to be much more frequent than in some other model species (like medaka) [40]. A single chromosome fusion seemed to be the only difference between the karyotypes of both Osteoglossum species since the OFE-1 probe hybridized to four chromosomes in O. bicirrhosum. Accordingly, the karyotype found in the sister group (herein represented by Arapaima gigas [Arapaiminae = Heterotidinae]) was also 2n = 56 and formed by acrocentric chromosomes. Based on these observations, it is plausible to hypothesize that multiple chromosomal fusions took place during the karyotype evolution of the arowana species in Asia and Australia, thereby reducing the 2n in the other Scleropages species.

3.2. Sex Chromosomes in Scleropages formosus?

Recently, genomic and cytogenetic analyses in the Asian arowana S. formosus revealed a 2n = 48 and the putative presence of a ZZ/ZW sex chromosome system [40]. This observation was based on the fact that the female and male karyotypes differed in the presence of one or two large chromosomes, bearing a conspicuous heterochromatic GC-rich block in the pericentromeric region, variable in length. However, the deeper cytogenetic analyses in our study clearly demonstrates that 2n = 50 is the correct chromosome count for this species (shared in several color variants; Cioffi, M.B. personal observation/unpublished results), corresponding to i) results of a previous study [44] and ii) the presence of 25 linkage groups in its reference genome [40,52]. On the other hand, we cannot exclude the possibility that some populations of S. formosus differ in their 2n. Moreover, our analyses focused on the putative ZW sex system in S. formosus but gave no support for the existence of heteromorphic sex chromosomes. Instead, the presence of size polymorphism in the 18th NOR-bearing chromosome pair was observed. A similar scenario was also observed for newts belonging to the genus Triturus (Amphibia, Salamandridae), where the large heteromorphic chromosome 1 was first thought to be ZW sex chromosome [53] but was later demonstrated to be related to an old balanced lethal system maintained by inversions [54]. In comparative fish cytogenetics, several studies reported the presence of sex chromosome systems based on this reasoning, but when later re-evaluated, the main cause of such observations was the presence of simple and commonly occurring size polymorphisms of the rDNA regions [55,56]. Sometimes, major rDNA sites (i.e., NOR sites) can show extensive size variation among homologs. It is widely accepted that heterochromatin polymorphisms related to such size NOR polymorphism play an important role in the sex chromosome evolution in fishes, by suppressing crossing over and triggering the initial steps of differentiation of the sex pair [57,58,59,60]. However, CGH and Zoo-Fish experiments applied in this study did not bring any evidence of accumulation of sex-specific or enriched repetitive sequences that may point to a putative sex-specific region (Figure 6, Supplementary Figure S2: CGH on metaphase of S. formosus).

3.3. Comparison of Cytogenetics of Arowana Species and Other Osteoglossiform Representatives

The karyotype differentiation among arowana species contrasts with the evolutionary karyotype divergence found in other osteoglossiform lineages. Notopteroidei, the sister group of Osteoglossidae, whose species diverged more than 100 MYA [17], has a conserved karyotype structure and 2n is maintained across species over a long evolutionary time scale, with only slight disturbances of collinearity [43]. Considerable variation with regards to the number and position of rDNA sites highlights these regions as diagnostic cytotaxonomic markers for Osteoglossinae. It is well known that rDNA regions are very dynamic in fish genomes [61,62,63], evolving several times in association with rearrangements (e.g., References [64,65]).

3.4. Biogeography of Osteoglossinae

The topology of our phylogenetic tree was congruent with most of the previous studies showing Osteoglossum as the sister group of Scleropages, and S. formosus as the sister group of Australian Scleropages (e.g., Reference [17]). From this topology, we could deduce that the intercontinental distribution of extant Osteoglossinae was the result of two biogeographical asynchronous events. The first event should explain the split between Osteoglossum (South America) and Scleropages (Sahul + Southeast Asia), while the second event should explain the trans-Wallace’s line distribution of Scleropages. There are two main hypotheses to explain the distribution of each of these intercontinental patterns (see below). One difficulty when studying the biogeography of Osteoglossinae is that the phylogeny of its extant species does not allow us to suggest the most likely region of origin of this group (see Reference [6]). The absence of any direct intercontinental connection between South America and Southeast Asia suggests that the distribution of the Osteoglossinae ancestor did not span these two regions. Consequently, the Australian region, which was directly or indirectly connected to both regions, could have played a central role in the biogeography of this group. On the other hand, there is weak evidence that the ancestral region of Osteoglossinae could include South America (but not Southeast Asia) because Arapaima (Arapaiminae/Heterotidinae) shares the same distribution with Osteoglossum. However, the fossil record does not provide clear evidence on that question because the phylogenetic positions of most of the osteoglossin fossils need to be reevaluated.
The last terrestrial connection between South America and Australia (through Antarctica) is estimated to 50–40 MYA [66]. If the divergence time between Osteoglossum and Scleropages was equal to or older than 50–40 MYA, then the vicariant hypothesis mediated by the final separation between Australia and South America cannot be rejected. Alternatively, if the divergence time is significantly younger than 40 MYA, the vicariant hypothesis will be rejected, and a marine dispersal will be preferred. Our divergence time between Osteoglossum and Scleropages (55–47.8 MYA) overlaps with the period of final contact between Australia and South America. Consequently, our results do not reject the tectonic-mediated vicariant hypothesis as the cause of the split between Osteoglossum and Scleropages [6,66].
Scleropages is a fully-restricted freshwater fish group found on both sides of Wallace’s line, a deep marine corridor marking the limit between the Southeast Asian and Sahul biogeographical regions. Considering the geographical distribution of Scleropages, we can a priori consider two hypotheses. The “Indian biotic ferry” hypothesis stipulates that the most recent common ancestor of Scleropages lived in Australia/India before these two continental plates separated from each other, 115–105 MYA [67]. Then, the ancestors of Southeast Asian Scleropages were transported by the Indian plate before dispersing to Southeast Asia after the collision between India and Eurasia. If this hypothesis is correct, the divergence time between the Southeast Asian and Australian Scleropages must overlap with the final fragmentation between India and Australia (approximately 105 MYA). Our results unambiguously reject this hypothesis: lineages of Southeast Asian arowana (S. formosus) and Australian arowanas (S. leichardti and S. jardinii) diverged from each other ~35 MYA (Figure 1), well after the separation of India and Australia. At that time, Australia was already isolated by vast marine environments, thereby making the hypothesis of marine dispersal of Scleropages to Southeast Asia the most likely. Our results call for a taxonomic revision of the extinct marine osteoglossomorphs and osteoglossid fossils to determine the extent to which a long-distance marine dispersal might have shaped the distribution of these fishes [9,32,68].
We note that our age estimation of Scleropages was substantially different from the previously proposed estimations. For example, Lavoué [16] estimated the age of the crown group Scleropages to a minimum of about 67 MYA (within a 95% credibility interval) and the age of the crown group Australian Scleropages to about 49 MYA. In our study, the divergence between S. leichardti and S. jardinii was estimated to be only 9 MYA. Heterogeneity in the evolutionary molecular rate of the mitogenomes used in Lavoué [16], as well as the distinct features of the molecular markers used herein (a high number of SNPs distributed along the genome), that are less affected by potential idiosyncrasies of using only mitogenomic regions [21], could explain most of these dating differences. Furthermore, the estimated divergence of the two outgroups used (Arapaima and Heterotis) was also more recent than estimates based on mtDNA [16,69] and was similar to recent studies with both mtDNA and nuclear markers [6,17].
The split of the South American species, O. ferreirai and O. bicirrhosum, is estimated to 6 MYA (Figure 1). The diversification of South American Osteoglossum species in Amazonia is coincident with the formation of the transcontinental Amazon River system over a period of about 4.9–5.6 million years through several river capture events [70]. The effects of river capture on speciation are complex, but it can subdivide the populations in new watersheds, thereby promoting the allopatric speciation [71].
The integration of cytogenetic and genomic approaches applied to the arowana species provided a clear pattern of phylogenetic relationships and evolutionary aspects of this ancient fish group. DArTseq data accessing a broad representation of the genome have revealed that the evolutionary diversification of the group is associated with both vicariant and dispersal events. The final fragmentation of southern Gondwanan regions explains the disjunct distribution of the genera Osteoglossum and Scleropages. The intercontinental distribution of species of Scleropages is better explained by a long-distance marine dispersal event during the late Eocene (about 35 MYA) between Australia–New Guinea and Southeast Asia.
Finally, the detailed cytogenetic survey indicated that the cytogenomic divergence patterns of Osteoglossinae were largely concordant with the inferred phylogenetic tree. Additionally, our study also enabled a precise karyotype revision leading to a correction of 2n and karyotype structures, as well as providing evidence of the absence of the heteromorphic ZW sex chromosome system in S. formosus. Further analyses are needed to detail the context of recent lineage diversification and the local adaptation of the S. formosus color varieties.

4. Materials and Methods

4.1. Individuals

The number and sex of individuals investigated are presented in Table 1. The samples were collected with the authorization of the Brazilian environmental agency ICMBio/ SISBIO (License No. 48290-1) and SISGEN (A96FF09). All species were identified by morphological criteria, and voucher specimens of S. formosus, S. jardinii, and S. leichardti were deposited under numbers 20558, 20563, and 20564 at the Museum of Universidade Estadual Paulista (UNESP, Botucatu). The specimens of O. bicirrhosum and O. ferreirai were deposited at the Museum of Zoology of the University of São Paulo (MZUSP), under voucher numbers 121638 and 121640. The Australian specimens were processed as approved by the University of Canberra animal ethics committee (AEC 20180447).

4.2. DArTseq Genotyping and Genetic Relationships

Liver fragments of all individuals were collected and stored in 100% ethanol. The DNA extractions were performed following Sambrook and Russell [72]. Obtained DNAs were submitted to DArTseq enrichment protocol with PstI and SphI enzymes [73] and sequenced on the Illumina Hiseq2500 platform by the Diversity Arrays Technology Company (Canberra, Australia). The raw data generated by sequencing was filtered, processed, and converted to high-quality genotypes by the facility, using proprietary DArT software. Genotypes were coded as an SNP matrix with loci in the rows and individuals in the columns. For each genotype, the data was stored as 0 for reference state homozygotes, 1 for heterozygotes, and 2 for alternate state homozygotes. The R-package dartR [74] was used to filter reads with more than one SNP, leaving only the SNP with higher information content. This filtered dataset was used in all subsequent analyses. The distribution of genetic diversity between species was visualized with a PCoA, also in dartR [74].

4.3. Species Tree and Divergence Times

The SNP matrix was converted to the VCF format with the Radiator R-package [75] and used as input for SVDquartets [76], implemented as part of PAUP 4.0a164 [77], to estimate the species relationships with a species tree, with default parameters. The program was set to evaluate all possible quartets using 10,000 bootstrap replicates. The generated tree was visualized in FigTree 1.4.3.
The package SNAPP in BEAST 2.5.1 [78] was also used to infer the species trees and to estimate the divergence times. The XML input file was generated with the “snapp_prep.rb” script, written by Stange et al. [79]. This script prepares the input and filters the dataset, removing monomorphic SNPs and those with missing data. The analysis was carried out with two calibration points, the first one (F1 in Figure 1) in the node leading to the Osteoglossinae species (Scleropages and Osteoglossum), which was set as an exponential prior with an offset of 48.0 MYA and mean of 5.0, corresponding to the age of the earliest almost complete fossil of Scleropages, S. sinensis [80]. The second prior (F2 in Figure 1) was placed in the node marking the Osteoglossidae division time, that includes all arowana utilized as outgroups Arapaima and Heterotis (Arapaiminae = Heterotidinae). We used an exponential distribution with an offset of 72.1 MYA and mean 11.0 that was based on the oldest known crown-group osteoglossid fossil [16]. The analysis was performed using a chain length of ten million generations, with sampling at every 5000 generations. Convergence levels in the run were assessed in Tracer 1.7.1 [81]. TreeAnnotator 2.5.1 was used to infer the MCC tree based on common ancestor heights. Burn-in was set to discard the first 25% generated trees, and the consensus tree was exported in FigTree 1.4.3.

4.4. Chromosome Preparations, C- and CMA3 Banding

Mitotic chromosomes were obtained using the protocol described in Bertollo et al. [82]. The experiments followed ethical and anesthesia conducts, following the Ethics Committee on Animal Experimentation of the Universidade Federal de São Carlos (Process number CEUA 1853260315). Chromomycin A3 (CMA3, DNA dye–specific for GC-rich regions) and DAPI (AT-specific) fluorescent staining was performed as described by Schmid [83]. Constitutive heterochromatin was visualized using C-banding following Sumner [84].

4.5. Fluorescence In Situ Hybridization (FISH) for Repetitive DNA Mapping

The 5S rDNA probe included the 5S rDNA coding region, with 120 base pairs (bp), and the 200 bp long non-transcribed spacer (NTS) [85]. The 18S rDNA probes were obtained by PCR using primers described in Cioffi et al. [86]). The 18S and 5S rDNA probes were labeled directly with the Nick-translation labeling kit (Jena Bioscience, Jena, Germany), where 18S rDNA was labeled with Atto488 (green fluorescence) and 5S rDNA with Atto550 (red fluorescence), according to the manufacturer’s manual. Since karyotypes of both Australian species contain the highest proportion of metacentric (m) chromosomes among arowana species, telomeric (TTAGGG)n sequences were mapped to track the possible fusion events using the PNA Telomere FISH Kit/Cy3 (DAKO, Glostrup, Denmark). FISH was conducted under high stringency conditions as described in Yano et al. [87].

4.6. Comparative Genomic Hybridization (CGH)

The total genomic DNAs (gDNAs) were extracted from liver tissue using the standard phenol-chloroform-isoamyl alcohol method [72]. Two different experimental designs were used in this study: (1) In a set of interspecific comparative experiments, the gDNA of S. leichardti was co-hybridized subsequently with the gDNA of each arowana species under study against the background of female chromosomes of S. leichardti. The gDNA of S. leichardti was directly labeled with Atto550 using a Nick-translation labeling kit (Jena Bioscience), while the gDNAs of all other arowana species were labeled with Atto488 also using a Nick-translation labeling kit (Jena Bioscience). In all experiments, C0t-1 DNA (i.e., a fraction of genomic DNA enriched for highly and moderately repetitive sequences) was used and prepared according to Zwick et al. [88], for blocking common genomic repetitive sequences. The final hybridization mixture for each slide (20 µL) was composed of 500 ng of S. leichardti gDNA, 500 ng of the gDNA of compared arowana species, and 15 µg of unlabeled female-derived C0t-1 DNA from the compared species, all resuspended together in the hybridization buffer containing 50% formamide, 2 x SSC, 10% SDS, 10% dextran sulfate, and Denhardt’s reagent (pH 7.0). The chosen ratio of probe versus the C0t-1 DNA amount was based on the experiments performed in our previous studies in fishes [87,89,90,91,92,93,94]. (2) Since a presence/absence polymorphism for conspicuous secondary constriction and a corresponding constitutive heterochromatin block appeared in a single chromosomal pair harboring in both male and female individuals of S. formosus, we compared the genomes of individuals carrying versus not carrying such a conspicuous block. The gDNA of individuals bearing the block was labeled with Atto550, and the gDNA of individuals lacking this region was labeled with Atto488 via Nick-translation as described above. The final probe cocktail for each experiment was composed of 500 ng of each probe and 15 µg of C0t-1 DNA of the respective individuals, diluted in the same hybridization buffer as described above. The CGH experiments were performed according to Symonová et al. [95].

4.7. Microdissection and the Preparation of Chromosome Painting Probes

Fifteen copies of the first chromosome pair of O. ferreirai and 12 copies of the largest acrocentric (that harbors a conspicuous secondary constriction) present in S. formosus were isolated via microdissection and amplified using the procedure described in Yang et al. [96]. We referred to these probes as OFE-1 and SFO-A, and they were labeled with Spectrum Green-dUTP and Spectrum-Orange-dUTP (Vysis, Downers Grove, IL, United States), respectively, in a secondary DOP PCR using 1µL of the primarily amplified product as a template DNA, also following Yang et al. [96]. Chromosomal preparations of all Arowana species were used for the Zoo-FISH experiments with both WCP probes. The hybridization was performed following the protocol described in Yano et al. [87,93].

4.8. Image Analysis and Processing

At least 30 metaphase spreads per individual were analyzed to confirm the 2n, karyotype structure, and FISH results. Images were captured using an Olympus BX50 microscope (Olympus Corporation, Ishikawa, Japan) with CoolSNAP and the images were processed using the Image Pro Plus 4.1 software (Media Cybernetics, Silver Spring, MD, USA). Chromosomes were classified as metacentric (m), submetacentric (sm), subtelocentric (st), or acrocentric (a), according to their arm ratios [97].

Supplementary Materials

Supplementary materials can be found at

Author Contributions

Conceptualization, M.d.B.C., P.R., T.L. and M.F.P.; Data curation, P.R.; Formal analysis, M.d.B.C., Z.M. and M.F.P.; Funding acquisition, M.d.B.C. and M.F.P.; Investigation, T.E., L.A.C.B., A.S., F.H.S.d.S., T.L., E.F., P.U. and A.T.; Methodology, M.d.B.C., S.L., E.A.d.O., F.H.S.d.S., Z.M., A.B.H.A.-R., C.F.Y., P.V., P.U., T.H. and M.F.P.; Project administration, M.d.B.C., L.A.C.B. and M.F.P.; Software, T.E. and S.L.; Supervision, M.d.B.C. and L.A.C.B.; Validation, P.R., T.E., S.L., W.F.M., Z.M., T.L., C.F.Y., P.U., T.H. and M.F.P.; Visualization, P.R., T.E., L.A.C.B., E.A.d.O., A.S., F.H.S.d.S., Z.M., A.B.H.A.-R., C.F.Y., P.V., E.F. and A.T.; Writing—original draft, M.d.B.C., P.R., T.L. and M.F.P.; Writing—review & editing, M.d.B.C., P.R., T.E., L.A.C.B., S.L., E.A.d.O., A.S., W.F.M., F.H.S.d.S., Z.M., T.L., A.B.H.A.-R., C.F.Y., P.V., E.F., P.U., T.H., A.T. and M.F.P.


This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (401962/2016-4 and 302449/2018-3 to M.B.C.), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) (2018/22033-1 to M.B.C.; and 2017/10240-0 to M.F.P.); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)/Alexander von Humboldt Foundation (88881.136128/2017-01 to M.B.C.). P.R. was supported by the project EXCELLENCE (CZ.02.1.01/0.0/0.0/15_003/0000460 OP). R.D.E, A.S. and P.R. were funded by the institutional support RVO: 67985904, A.S. was further supported by PPLZ: L200451751. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001


The authors would like to thank the great effort of all collaborators from four different continents who aided in analyzing the data. The study belongs to a series of cytogenetic and cytogenomic studies on Osteoglossiforms.

Conflicts of Interest

The authors declare no conflict of interest.


  1. Patterson, C.; Rosen, D.E. Review of ichthyodectiform and other Mesozoic teleost fishes, and the theory and practice of classifying fossils. Bull. AMNH 1977, 158, 2. [Google Scholar]
  2. Arratia, G. Basal Teleosts and teleostean phylogeny. Palaeo Ichthyol. 1997, 7, 5–168. [Google Scholar]
  3. Near, T.J.; Eytan, R.I.; Dornburg, A.; Kuhn, K.L.; Moore, J.A.; Davis, M.P.; Wainwright, P.C.; Friedman, M.; Smith, W.L. Resolution of ray-finned fish phylogeny and timing of diversification. Proc. Natl. Acad. Sci. USA 2012, 109, 13698–13703. [Google Scholar] [CrossRef] [PubMed][Green Version]
  4. Betancur-R, R.; Wiley, E.O.; Arratia, G.; Acero, A.; Bailly, N.; Miya, M.; Lecointre, G.; Orti, G. Phylogenetic classification of bony fishes. BMC Evol. Biol. 2017, 17, 162. [Google Scholar] [CrossRef] [PubMed]
  5. Nelson, J.S.; Grande, T.C.; Wilson, M.V.H. Fishes of the World, 5th ed.; John Wiley & Sons: Hoboken, NJ, USA, 2016; ISBN 111834233X. [Google Scholar]
  6. Hilton, E.J.; Lavoué, S. A review of the systematic biology of fossil and living bony-tongue fishes, Osteoglossomorpha (Actinopterygii: Teleostei). Neotrop. Ichthyol. 2018, 16, 1–35. [Google Scholar] [CrossRef]
  7. Fricke, R.; Eschmeyer, W.; van der Laan, R. Eschmeyer’s Catalog of Fishes: Genera, Species, References, California Academy of Sciences; California Academy of Sciences: San Francisco, CA, USA, 2019. [Google Scholar]
  8. Cavin, L.; Lionel. Freshwater Fishes: 250 Million Years of Evolutionary History; Press-Elsevier, I., Ed.; ISTE Press-Elsevier: London, UK, 2017; ISBN 9780081011416. [Google Scholar]
  9. Capobianco, A.; Friedman, M. Vicariance and dispersal in southern hemisphere freshwater fish clades: a palaeontological perspective. Biol. Rev. 2019, 94, 662–699. [Google Scholar] [CrossRef] [PubMed]
  10. Kottelat, M. The IUCN Red List of Threatened Species, Version 2014. Available online: (accessed on 10 July 2019).
  11. Roberts, T.R. Scleropages inscriptus, a new fish species from the Tananthayi or Tenasserim River basin, Malay Peninsula of Myanmar (Osteoglossidae: Osteoglossiformes). Aqua. Int. J. Ichthyol. 2012, 18, 113–118. [Google Scholar]
  12. Ng, P.K.L.; Tan, H.H. Freshwater fishes of Southeast Asia: potential for the aquarium fish trade and conservation issues. Aquarium Sci. Conserv. 1997, 1, 79–90. [Google Scholar] [CrossRef]
  13. Pouyaud, L.; Sudarto;Teugels, G.G. The different colour varieties of the asian arowana Scleropages formosus (Osteoglossidae) are distinct species: Morphologic and genetic evidences. Cybium 2003, 27, 287–305. [Google Scholar]
  14. Kottelat, M. The fishes of Danau Sentarum National Park and the Kapuas Lakes area, Kalimantan Barat, Indonesia. Raffles Bull Zool Suppl 2005, 13, 139–173. [Google Scholar]
  15. Inoue, J.G.; Kumazawa, Y.; Miya, M.; Nishida, M. The historical biogeography of the freshwater knifefishes using mitogenomic approaches: A Mesozoic origin of the Asian notopterids (Actinopterygii: Osteoglossomorpha). Mol. Phylogenet. Evol. 2009, 51, 486–499. [Google Scholar] [CrossRef] [PubMed]
  16. Lavoué, S. Testing a time hypothesis in the biogeography of the arowana genus Scleropages (Osteoglossidae). J. Biogeogr. 2015, 42, 2427–2439. [Google Scholar] [CrossRef]
  17. Lavoué, S. Was Gondwanan breakup the cause of the intercontinental distribution of Osteoglossiformes? A time-calibrated phylogenetic test combining molecular, morphological, and paleontological evidence. Mol. Phylogenet. Evol. 2016, 99, 34–43. [Google Scholar] [CrossRef] [PubMed]
  18. Hilton, E.J. Comparative osteology and phylogenetic systematics of fossil and living bony-tongue fishes (Actinopterygii, Teleostei, Osteoglossomorpha). Zool. J. Linn. Soc. 2003, 137, 1–100. [Google Scholar] [CrossRef]
  19. Knowles, L.L.; Maddison, W.P. Statistical phylogeography. Mol. Ecol. 2002, 11, 2623–2635. [Google Scholar] [CrossRef] [PubMed]
  20. Nielsen, R.; Beaumont, M.A. Statistical inferences in phylogeography. Mol. Ecol. 2009, 18, 1034–1047. [Google Scholar] [CrossRef] [PubMed]
  21. Edwards, S.V. Is a new and general theory of molecular systematics emerging? Evol. Int. J. Org. Evol. 2009, 63, 1–19. [Google Scholar] [CrossRef] [PubMed]
  22. Garrick, R.C.; Bonatelli, I.A.S.; Hyseni, C.; Morales, A.; Pelletier, T.A.; Perez, M.F.; Rice, E.; Satler, J.D.; Symula, R.E.; Thomé, M.T.C.; et al. The evolution of phylogeographic data sets. Mol. Ecol. 2015, 24, 1164–1171. [Google Scholar] [CrossRef] [PubMed][Green Version]
  23. Lemmon, E.M.; Lemmon, A.R. High-Throughput Genomic Data in Systematics and Phylogenetics. Annu. Rev. Ecol. Evol. Syst. 2013, 44, 99–121. [Google Scholar] [CrossRef][Green Version]
  24. McCormack, J.E.; Hird, S.M.; Zellmer, A.J.; Carstens, B.C.; Brumfield, R.T. Applications of next-generation sequencing to phylogeography and phylogenetics. Mol. Phylogenet. Evol. 2013, 66, 526–538. [Google Scholar] [CrossRef]
  25. Melville, J.; Haines, M.L.; Hale, J.; Chapple, S.; Ritchie, E.G. Concordance in phylogeography and ecological niche modelling identify dispersal corridors for reptiles in arid Australia. J. Biogeogr. 2016, 43, 1844–1855. [Google Scholar] [CrossRef]
  26. Morse, P.; Kjeldsen, S.R.; Meekan, M.G.; Mccormick, M.I.; Finn, J.K.; Huffard, C.L.; Zenger, K.R. Genome-wide comparisons reveal a clinal species pattern within a holobenthic octopod—the Australian Southern blue-ringed octopus, Hapalochlaena maculosa (Cephalopoda: Octopodidae). Ecol. Evol. 2018, 8, 2253–2267. [Google Scholar] [CrossRef] [PubMed]
  27. Georges, A.; Gruber, B.; Pauly, G.B.; White, D.; Adams, M.; Young, M.J.; Kilian, A.; Zhang, X.; Shaffer, H.B.; Unmack, P.J. Genomewide SNP markers breathe new life into phylogeography and species delimitation for the problematic short-necked turtles (Chelidae: Emydura) of eastern Australia. Mol. Ecol. 2018, 27, 5195–5213. [Google Scholar] [CrossRef] [PubMed]
  28. Unmack, P.J.; Young, M.J.; Gruber, B.; White, D.; Kilian, A.; Zhang, X.; Georges, A. Phylogeography and species delimitation of Cherax destructor (Decapoda: Parastacidae) using genome-wide SNPs. Mar. Freshw. Res. 2019, 70, 857–869. [Google Scholar] [CrossRef]
  29. Unmack, P.J.; Adams, M.; Bylemans, J.; Hardy, C.M.; Hammer, M.P.; Georges, A. Perspectives on the clonal persistence of presumed ‘ghost’genomes in unisexual or allopolyploid taxa arising via hybridization. Sci. Rep. 2019, 9, 4730. [Google Scholar] [CrossRef]
  30. Nelson, G.J. Infraorbital bones and their bearing on the phylogeny and geography of osteoglossomorph fishes. Am. Mus. Nov. 1969, 1–37. [Google Scholar]
  31. Cracraft, J. Continental drift and vertebrate distribution. Annu. Rev. Ecol. Syst. 1974, 5, 215–261. [Google Scholar] [CrossRef]
  32. Bonde, N. Osteoglossomorphs of the marine Lower Eocene of Denmark–with remarks on other Eocene taxa and their importance for palaeobiogeography. Geol. Soc. Lond. Spec. Publ. 2008, 295, 253–310. [Google Scholar] [CrossRef]
  33. Taverne, L. On the presence of the osteoglossid genus Scleropages in the Paleocene of Niger, Africa (Teleostei, Osteoglossomorpha). Bull. R. des Sci. Nat. Belgique. Sci. la terre 2009, 79, 161–167. [Google Scholar]
  34. Amemiya, C.T.; Alfoldi, J.; Lee, A.P.; Fan, S.; Philippe, H.; MacCallum, I.; Braasch, I.; Manousaki, T.; Schneider, I.; Rohner, N.; et al. The African coelacanth genome provides insights into tetrapod evolution. Nature 2013, 496, 311–316. [Google Scholar] [CrossRef][Green Version]
  35. Ráb, P.; Yano, C.F.; Lavoué, S.; Jegede, O.I.; Bertollo, L.A.C.; Ezaz, T.; Majtánová, Z.; de Oliveira, E.A.; Cioffi, M.B. Karyotype and Mapping of Repetitive DNAs in the African Butterfly Fish Pantodon buchholzi, the Sole Species of the Family Pantodontidae. Cytogenet. Genome Res. 2016, 149, 312–320. [Google Scholar] [CrossRef]
  36. Symonová, R.; Majtánová, Z.; Arias-Rodriguez, L.; Mořkovský, L.; Kořínková, T.; Cavin, L.; Pokorná, M.J.; Doležálková, M.; Flajšhans, M.; Normandeau, E.; et al. Genome Compositional Organization in Gars Shows More Similarities to Mammals than to Other Ray-Finned Fish. J. Exp. Zool. Part B Mol. Dev. Evol. 2017, 328, 607–619. [Google Scholar] [CrossRef]
  37. Majtánová, Z.; Symonová, R.; Arias-Rodriguez, L.; Sallan, L.; Ráb, P. “Holostei versus Halecostomi” Problem: Insight from Cytogenetics of Ancient Nonteleost Actinopterygian Fish, Bowfin Amia calva. J. Exp. Zool. Part B Mol. Dev. Evol. 2017, 328, 620–628. [Google Scholar] [CrossRef]
  38. Alda, F.; Tagliacollo, V.A.; Bernt, M.J.; Waltz, B.T.; Ludt, W.B.; Faircloth, B.C.; Alfaro, M.E.; Albert, J.S.; Chakrabarty, P. Resolving Deep Nodes in an Ancient Radiation of Neotropical Fishes in the Presence of Conflicting Signals from Incomplete Lineage Sorting. Syst. Biol. 2018, 68, 573–593. [Google Scholar] [CrossRef][Green Version]
  39. Ozouf-Costaz, C.; Coutanceau, J.-P.; Bonillo, C.; Belkadi, L.; Fermon, Y.; Agnèse, J.-F.; Guidi-Rontani, C.; Paugy, D.; Agnese, J.F.; Guidi-Rontani, C.; et al. First insights into karyotype evolution within the family Mormyridae. Cybium 2015, 39, 227–236. [Google Scholar]
  40. Bian, C.; Hu, Y.; Ravi, V.; Kuznetsova, I.S.; Shen, X.; Mu, X.; Sun, Y.; You, X.; Li, J.; Li, X.; et al. The Asian arowana (Scleropages formosus) genome provides new insights into the evolution of an early lineage of teleosts. Sci. Rep. 2016, 6, 1–17. [Google Scholar] [CrossRef]
  41. Hatanaka, T.; de Oliveira, E.A.; Ráb, P.; Yano, C.F.; Bertollo, L.A.C.; Ezaz, T.; Jegede, O.O.I.; Liehr, T.; Olaleye, V.F.; de Bello Cioffi, M. First chromosomal analysis in Gymnarchus niloticus (Gymnarchidae: Osteoglossiformes): insights into the karyotype evolution of this ancient fish order. Biol. J. Linn. Soc. 2018, 125, 83–92. [Google Scholar] [CrossRef]
  42. Barby, F.; Rab, P.; Lavoue, S.; Ezaz, T.; Bertollo, L.A.C.; Kilian, A.; Maruyama, S.R.; Oliveira, E.A.; Artoni, R.F.; Santos, M.H.; et al. From chromosomes to genome: insights into the evolutionary relationships and biogeography of Old World knifefishes (Notopteridae; Osteoglossiformes). Genes 2018, 9, 306. [Google Scholar] [CrossRef]
  43. Barby, F.F.; Bertollo, L.A.C.; de Oliveira, E.A.; Yano, C.F.; Hatanaka, T.; Ráb, P.; Sember, A.; Ezaz, T.; Artoni, R.F.; Liehr, T.; et al. Emerging patterns of genome organization in Notopteridae species (Teleostei, Osteoglossiformes) as revealed by Zoo-FISH and Comparative Genomic Hybridization (CGH). Sci. Rep. 2019, 9, 1112. [Google Scholar] [CrossRef]
  44. Urushido, T. Karyotype of three species of fishes in the order Osteoglossiformes. Chromosom. Inform. Serv. 1975, 18, 20–22. [Google Scholar]
  45. Magtoon, W.; Donsakul, T. Morphology and cytogenetics of Arowana fishes in subfamily Osteoglossinae from Asia, Australia and South America. In Proceedings of the 30th Congress on Science and Technology of Thailand, Bangkok, Thailand, 26–30 January 2004; pp. 9–21. [Google Scholar]
  46. Shen, X.Y.; Kwan, H.Y.; Thevasagayam, N.M.; Prakki, S.R.S.; Kuznetsova, I.S.; Ngoh, S.Y.; Lim, Z.; Feng, F.; Chang, A.; Orbán, L. The first transcriptome and genetic linkage map for Asian arowana. Mol. Ecol. Resour. 2014, 14, 622–635. [Google Scholar] [CrossRef]
  47. Hirata, J.; Urushido, T. Karyotypes and DNA content in the Osteoglossiformes. Sci Rep Res Inst Evol Biol 2000, 9, 83–90. [Google Scholar]
  48. Suzuki, A.; Taki, Y.; Urushido, T. Karyotypes of two species of arowana, Osteoglossum bicirrhosum and O. ferreirai. Jpn. J. Ichthyol. 1982, 29, 220–222. [Google Scholar]
  49. Lim, K.Y.; Kovarik, A.; Matyasek, R.; Chase, M.W.; Clarkson, J.J.; Grandbastien, M.A.; Leitch, A.R. Sequence of events leading to near-complete genome turnover in allopolyploid Nicotiana within five million years. New Phytol. 2007, 175, 756–763. [Google Scholar] [CrossRef]
  50. Majka, J.; Majka, M.; Kwiatek, M.; Wiśniewska, H. Similarities and differences in the nuclear genome organization within Pooideae species revealed by comparative genomic in situ hybridization (GISH). J. Appl. Genet. 2017, 58, 151–161. [Google Scholar] [CrossRef]
  51. Sember, A.; Bertollo, L.A.C.; Ráb, P.; Yano, C.F.; Hatanaka, T.; de Oliveira, E.A.; Cioffi, M.d.B. Sex Chromosome Evolution and Genomic Divergence in the Fish Hoplias malabaricus (Characiformes, Erythrinidae). Front. Genet. 2018, 9, 1–12. [Google Scholar] [CrossRef]
  52. Li, J.; Bian, C.; Hu, Y.; Mu, X.; Shen, X.; Ravi, V.; Kuznetsova, I.S.; Sun, Y.; You, X.; Qiu, Y.; et al. A chromosome-level genome assembly of the Asian arowana, Scleropages formosus. Sci. Data 2016, 3, 160105. [Google Scholar] [CrossRef]
  53. Callan, H.G.; Lloyd, L. Lampbrush chromosomes of crested newts Triturus cristatus (Laurenti). Philos. Trans. R. Soc. Lond. B. Biol. Sci. 1960, 243, 135–219. [Google Scholar]
  54. Sims, S.H.; Macgregor, H.C.; Pellatt, P.S.; Horner, H.A. Chromosome 1 in crested and marbled newts (Triturus). Chromosoma 1984, 89, 169–185. [Google Scholar] [CrossRef]
  55. Galetti, P.M.; Foresti, F.; Bertollo, L.A.C.; Moreira Filho, O. Heteromorphic sex chromosomes in three species of the genus Leporinus (Pisces, Anostomidae). Cytogenet Cell Genet 1981, 29, 138–142. [Google Scholar] [CrossRef]
  56. Mestriner, C.A.; Bertollo, L.A.C.; Galetti, P.M. Chromosome banding and synaptonemal complexes in Leporinus lacustris (Pisces, Anostomidae): analysis of a sex system. Chromosom. Res. 1995, 3, 440–443. [Google Scholar] [CrossRef]
  57. Reed, K.M.; Phillips, R.B. Polymorphism of the nucleolus organizer region (NOR) on the putative sex chromosomes of Arctic char (Salvelinus alpinus) is not sex related. Chromosom. Res 1997, 5, 221–227. [Google Scholar] [CrossRef]
  58. Molina, W.F.; Schmid, M.; Galetti, P.M. Heterochromatin and sex chromosomes in the Neotropical fish genus Leporinus (Characiformes, Anostomidae). Cytobios 1998, 94, 141–149. [Google Scholar]
  59. Charlesworth, D.; Charlesworth, B.; Marais, G. Steps in the evolution of heteromorphic sex chromosomes. Heredity 2005, 95, 118–128. [Google Scholar] [CrossRef][Green Version]
  60. Cioffi, M.B.; Moreira-Filho, O.; Almeida-Toledo, L.F.; Bertollo, L.A.C. The contrasting role of heterochromatin in the differentiation of sex chromosomes: an overview from Neotropical fishes. J. Fish Biol. 2012, 80, 2125–2139. [Google Scholar] [CrossRef]
  61. Gornung, E. Twenty years of physical mapping of major ribosomal RNA genes across the teleosts: a review of research. Cytogenet. Genome Res. 2013, 141, 90–102. [Google Scholar] [CrossRef]
  62. Sember, A.; Bohlen, J.; Šlechtová, V.; Altmanová, M.; Symonová, R.; Ráb, P. Karyotype differentiation in 19 species of river loach fishes (Nemacheilidae, Teleostei): Extensive variability associated with rDNA and heterochromatin distribution and its phylogenetic and ecological interpretation. BMC Evol. Biol. 2015, 15, 251–272. [Google Scholar] [CrossRef]
  63. Symonová, R.; Howell, W. Vertebrate Genome Evolution in the Light of Fish Cytogenomics and rDNAomics. Genes 2018, 9, 96. [Google Scholar] [CrossRef]
  64. Molina, W.F.; Galetti, P.M. Robertsonian rearrangements in the reef fish Chromis (Perciformes, Pomacentridae) involving chromosomes bearing 5S rRNA genes. Genet. Mol. Biol. 2002, 25, 373–377. [Google Scholar] [CrossRef]
  65. Getlekha, N.; Molina, W.F.; de Bello Cioffi, M.; Yano, C.F.; Maneechot, N.; Bertollo, L.A.C.; Supiwong, W.; Tanomtong, A. Repetitive DNAs highlight the role of chromosomal fusions in the karyotype evolution of Dascyllus species (Pomacentridae, Perciformes). Genetica 2016, 144, 203–211. [Google Scholar] [CrossRef]
  66. Van Den Ende, C.; White, L.T.; van Welzen, P.C. The existence and break-up of the Antarctic land bridge as indicated by both amphi-Pacific distributions and tectonics. Gondwana Res. 2017, 44, 219–227. [Google Scholar] [CrossRef][Green Version]
  67. Ali, J.R.; Krause, D.W. Late Cretaceous bioconnections between Indo-Madagascar and Antarctica: refutation of the Gunnerus Ridge causeway hypothesis. J. Biogeogr. 2011, 38, 1855–1872. [Google Scholar] [CrossRef]
  68. Wilson, M.V.H.; Murray, A.M. Osteoglossomorpha: phylogeny, biogeography, and fossil record and the significance of key African and Chinese fossil taxa. Geol. Soc. Lond. Spec. Publ. 2008, 295, 185–219. [Google Scholar] [CrossRef]
  69. Kumazawa, Y.; Nishida, M. Molecular phylogeny of osteoglossoids: A new model for Gondwanian origin and plate tectonic transportation of the Asian arowana. Mol. Biol. Evol. 2000, 17, 1869–1878. [Google Scholar] [CrossRef]
  70. Winn, C.; Karlstrom, K.E.; Shuster, D.L.; Kelley, S.; Fox, M. 6 Ma age of carving Westernmost Grand Canyon: Reconciling geologic data with combined AFT,(U–Th)/He, and 4He/3He thermochronologic data. Earth Planet. Sci. Lett. 2017, 474, 257–271. [Google Scholar] [CrossRef]
  71. Albert, J.S.; Val, P.; Hoorn, C. The changing course of the Amazon River in the Neogene: center stage for Neotropical diversification. Neotrop. Ichthyol. 2018, 16, e180033. [Google Scholar] [CrossRef]
  72. Sambrook, J.; Russell, D.W. Molecular Cloning: A Laboratory Manual, 3rd ed.; Cold Spring Harbor Laboratory Press: New York, NY, USA, 2001. [Google Scholar]
  73. Kilian, A.; Wenzl, P.; Huttner, E.; Carling, J.; Xia, L.; Blois, H.; Caig, V.; Heller-Uszynska, K.; Jaccoud, D.; Hopper, C. Diversity arrays technology: a generic genome profiling technology on open platforms. In Data Production and Analysis in Population Genomics; Springer: New York, NY, USA, 2012; pp. 67–89. [Google Scholar]
  74. Gruber, B.; Unmack, P.J.; Berry, O.F.; Georges, A. dartr: An r package to facilitate analysis of SNP data generated from reduced representation genome sequencing. Mol. Ecol. Resour. 2018, 18, 691–699. [Google Scholar] [CrossRef]
  75. Gosselin, T. RADseq Data Exploration, Manipulation and Visualization Using R. 2016. Available online: (accessed on 10 July 2019). [CrossRef]
  76. Chifman, J.; Kubatko, L. Quartet Inference from SNP Data Under the Coalescent Model. Bioinformatics 2014, 30, 3317–3324. [Google Scholar] [CrossRef][Green Version]
  77. Swofford, D.L. PAUP*. Phylogenetic Analysis Using Parsimony and Other Methods; Sinauer Associates, Inc.: Sunderland, MA, USA, 2003. [Google Scholar]
  78. Bouckaert, R.; Heled, J.; Kühnert, D.; Vaughan, T.; Wu, C.-H.; Xie, D.; Suchard, M.A.; Rambaut, A.; Drummond, A.J. BEAST 2: A Software Platform for Bayesian Evolutionary Analysis. PLOS Comput. Biol. 2014, 10, e1003537. [Google Scholar] [CrossRef]
  79. Stange, M.; Sánchez-Villagra, M.R.; Salzburger, W.; Matschiner, M. Bayesian Divergence-Time Estimation with Genome-Wide Single-Nucleotide Polymorphism Data of Sea Catfishes (Ariidae) Supports Miocene Closure of the Panamanian Isthmus. Syst. Biol. 2018, 67, 681–699. [Google Scholar] [CrossRef]
  80. Zhang, J.-Y.; Wilson, M.V.H. First complete fossil Scleropages (Osteoglossomorpha). Vertebr. Palasiat. 2017, 55, 1–23. [Google Scholar]
  81. Rambaut, A.; Drummond, A.J.; Xie, D.; Baele, G.; Suchard, M.A. Posterior Summarization in Bayesian Phylogenetics Using Tracer 1.7. Syst. Biol. 2018, 67, 901–904. [Google Scholar] [CrossRef] [PubMed][Green Version]
  82. Bertollo, L.A.C.; Cioffi, M.B.; Moreira-Filho, O. Direct chromosome preparation from Freshwater Teleost Fishes. In Fish Cytogenetic Techniques (Chondrichthyans and Teleosts); Ozouf-Costaz, C., Pisano, E., Foresti, F., Almeida Toledo, L.F., Eds.; CRC Press: Enfield, CT, USA, 2015; pp. 21–26. [Google Scholar]
  83. Schmid, M. Chromosome banding in Amphibia. IV. Differentiation of GC-and AT-rich chromosome regions in Anura. Chromosoma 1980, 77, 83–103. [Google Scholar] [CrossRef] [PubMed]
  84. Sumner, A.T. A simple technique for demonstrating centromeric heterochromatin. Exp. Cell Res. 1972, 75, 304–306. [Google Scholar] [CrossRef]
  85. Pendás, A.M.; Móran, P.; Freije, J.P.; Garcia-Vásquez, E. Chromosomal location and nucleotide sequence of two tandem repeats of the Atlantic salmon 5S rDNA. Cytogenet Cell Genet 1994, 67, 31–36. [Google Scholar] [CrossRef] [PubMed]
  86. Cioffi, M.B.; Martins, C.; Centofante, L.; Jacobina, U.; Bertollo, L.A.C. Chromosomal Variability among Allopatric Populations of Erythrinidae Fish Hoplias malabaricus: Mapping of Three Classes of Repetitive DNAs. Cytogenet. Genome Res. 2009, 125, 132–141. [Google Scholar] [CrossRef] [PubMed]
  87. Yano, C.F.; Bertollo, L.A.C.; Cioffi, M.B. Fish-FISH: molecular cytogenetics in fish species. In Fluorescence In Situ Hybridization (FISH)- Application Guide; Liehr, T., Ed.; Springer: Berlin, Germany, 2017; pp. 429–444. [Google Scholar]
  88. Zwick, M.S.; Hanson, R.E.; Mcknight, T.D.; Islam-Faridi, M.H.; Stelly, D.M.; Wing, R.A.; Price, H.J. A rapid procedure for the isolation of C 0 t-1 DNA from plants. Genome 1997, 40, 138–142. [Google Scholar] [CrossRef] [PubMed]
  89. Symonová, R.; Majtánová, Z.; Sember, A.; Staaks, G.B.O.; Bohlen, J.; Freyhof, J. Genome differentiation in a species pair of coregonine fishes: an extremely rapid speciation driven by stress - activated retrotransposons mediating extensive ribosomal DNA multiplications. BMC Evol. Biol. 2013, 13, 42–52. [Google Scholar] [CrossRef]
  90. Symonová, R.; Flajšhans, M.; Sember, A.; Havelka, M.; Gela, D.; Kořínková, T.; Rodina, M.; Rábová, M.; Ráb, P. Molecular cytogenetics in artificial hybrid and highly polyploid sturgeons: an evolutionary story narrated by repetitive sequences. Cytogenet. Genome Res. 2013, 141, 153–162. [Google Scholar] [CrossRef]
  91. Carvalho, P.C.; de Oliveira, E.A.; Bertollo, L.A.C.; Yano, C.F.; Oliveira, C.; Decru, E.; Jegede, O.I.; Hatanaka, T.; Liehr, T.; Al-Rikabi, A.B.H.; et al. First Chromosomal Analysis in Hepsetidae (Actinopterygii, Characiformes): Insights into Relationship between African and Neotropical Fish Groups. Front. Genet. 2017, 8, 203. [Google Scholar] [CrossRef][Green Version]
  92. De Freitas, N.L.; Al-Rikabi, A.B.H.; Bertollo, L.A.C.; Ezaz, T.; Yano, C.F.; de Oliveira, E.A.; Hatanaka, T.; de Bello Cioffi, M. Early Stages of XY Sex Chromosomes Differentiation in the Fish Hoplias malabaricus (Characiformes, Erythrinidae) Revealed by DNA Repeats Accumulation. Curr. Genom. 2018, 19, 216–226. [Google Scholar] [CrossRef] [PubMed]
  93. De Moraes, R.L.R.; Bertollo, L.A.C.; Marinho, M.M.F.; Yano, C.F.; Hatanaka, T.; Barby, F.F.; Troy, W.P.; Cioffi, M.d.B. Evolutionary Relationships and Cytotaxonomy Considerations in the Genus Pyrrhulina (Characiformes, Lebiasinidae). Zebrafish 2017, 14, 536–546. [Google Scholar] [CrossRef] [PubMed]
  94. De Oliveira, E.A.; Sember, A.; Bertollo, L.A.C.; Yano, C.F.; Ezaz, T.; Moreira-Filho, O.; Hatanaka, T.; Trifonov, V.; Liehr, T.; Al-Rikabi, A.B.H.; et al. Tracking the evolutionary pathway of sex chromosomes among fishes: characterizing the unique XX/XY1Y2 system in Hoplias malabaricus (Teleostei, Characiformes). Chromosoma 2018, 127, 115–128. [Google Scholar] [CrossRef] [PubMed]
  95. Symonová, R.; Sember, A.; Majtánová, Z.; Ráb, P. Characterization of fish genomes by GISH and CGH. In Fish Cytogenetic Techniques. Ray-Fin Fishes and Chondrichthyans; CCR Press: Boca Raton, FL, USA, 2015; pp. 118–131. [Google Scholar]
  96. Yang, F.; Trifonov, V.; Ng, B.L.; Kosyakova, N.; Carter, N.P. Generation of paint probes by flow-sorted and microdissected chromosomes. In Fluorescence In Situ Hybridization (FISH)—Application Guide; Liehr, T., Ed.; Springer: Berlin/Heidelberg, Germany, 2009; pp. 35–52. [Google Scholar]
  97. Levan, A.; Fredga, K.; Sandberg, A.A. Nomenclature for centromeric position on chromosomes. Hereditas 1964, 52, 201–220. [Google Scholar] [CrossRef]
Figure 1. The geographic distribution of arowana, showing species color-coded by potential occurrence in South America (O. bicirrhosum, light green; O. ferreirai, dark green), Asia (S. formosus, red; S. inscriptus, blue), and Australia (S. jardinii, dark pink; S. leichardti, light pink). The consensus dated species tree given by SNAPP is shown, with estimated (average) divergence time in bold and 95% highest posterior density (HPD) intervals inside brackets for each node. Support is coded using circles in each node, and fossil calibrated nodes are indicated by arrows. Circles in the tips represent each species, with the same color used in the map, and numbers inside the circles represent the diploid chromosome number (2n) for each species. A geological scale with the main periods is depicted on the left (N = Neogene; P = Paleogene; C = Cretaceous).
Figure 1. The geographic distribution of arowana, showing species color-coded by potential occurrence in South America (O. bicirrhosum, light green; O. ferreirai, dark green), Asia (S. formosus, red; S. inscriptus, blue), and Australia (S. jardinii, dark pink; S. leichardti, light pink). The consensus dated species tree given by SNAPP is shown, with estimated (average) divergence time in bold and 95% highest posterior density (HPD) intervals inside brackets for each node. Support is coded using circles in each node, and fossil calibrated nodes are indicated by arrows. Circles in the tips represent each species, with the same color used in the map, and numbers inside the circles represent the diploid chromosome number (2n) for each species. A geological scale with the main periods is depicted on the left (N = Neogene; P = Paleogene; C = Cretaceous).
Ijms 20 04296 g001
Figure 2. Principal coordinate analysis plot of genetic diversity in arowana species strongly corresponds to their geographical distribution. OB = O. bicirrhosum; OF = O. ferreirai; SF = S. formosus; SJ = S. jardinii; SL = S. leichardti.
Figure 2. Principal coordinate analysis plot of genetic diversity in arowana species strongly corresponds to their geographical distribution. OB = O. bicirrhosum; OF = O. ferreirai; SF = S. formosus; SJ = S. jardinii; SL = S. leichardti.
Ijms 20 04296 g002
Figure 3. Karyotypes of the silver arowana Osteoglossum bicirrhosum (A,B), black arowana Osteoglossum ferreirai (C,D), Asian arowana Scleropages formosus (E,F); northern saratoga Scleropages jardinii (G,H) and southern saratoga Scleropages leichardti (I,J) arranged from Giemsa-stained (A,C,E,G,I) and C-banded chromosomes (B,D,F,H,J). In boxes (E,F), the variant forms of the 18th chromosome pair of Asian arowana in relation to its C-positive heterochromatin content (for more details, please check Section 3.2 in the discussion section) Bar = 5 µm.
Figure 3. Karyotypes of the silver arowana Osteoglossum bicirrhosum (A,B), black arowana Osteoglossum ferreirai (C,D), Asian arowana Scleropages formosus (E,F); northern saratoga Scleropages jardinii (G,H) and southern saratoga Scleropages leichardti (I,J) arranged from Giemsa-stained (A,C,E,G,I) and C-banded chromosomes (B,D,F,H,J). In boxes (E,F), the variant forms of the 18th chromosome pair of Asian arowana in relation to its C-positive heterochromatin content (for more details, please check Section 3.2 in the discussion section) Bar = 5 µm.
Ijms 20 04296 g003
Figure 4. Karyotypes of the silver arowana Osteoglossum bicirrhosum (A,B), black arowana Osteoglossum ferreirai (C,D), Asian arowana Scleropages formosus (E,F); northern saratoga Scleropages jardinii (G,H) and southern saratoga Scleropages leichardti (I,J) arranged from chromosomes labeled with 5S rDNA (red) and 18S rDNA (green) probes after a dual-color FISH (A,C,E,G,I) and after CMA3/DAPI staining (B,D,F,H,J). In boxes, the different forms of the 18th chromosome pairs of Asian arowana with their heteromorphic 18S rDNA sites and CMA3+ signals. Bar = 5 µm.
Figure 4. Karyotypes of the silver arowana Osteoglossum bicirrhosum (A,B), black arowana Osteoglossum ferreirai (C,D), Asian arowana Scleropages formosus (E,F); northern saratoga Scleropages jardinii (G,H) and southern saratoga Scleropages leichardti (I,J) arranged from chromosomes labeled with 5S rDNA (red) and 18S rDNA (green) probes after a dual-color FISH (A,C,E,G,I) and after CMA3/DAPI staining (B,D,F,H,J). In boxes, the different forms of the 18th chromosome pairs of Asian arowana with their heteromorphic 18S rDNA sites and CMA3+ signals. Bar = 5 µm.
Ijms 20 04296 g004
Figure 5. Comparative genomic hybridization (CGH) in metaphase plates of the southern saratoga Scleropages leichardti. First column (A,E,I,M): DAPI images (blue); Second column (B,F,J,N): hybridization pattern using Scleropages leichardti gDNA probe (red); Third column (C,G,K,O): hybridization pattern using the gDNA (green) of the northern saratoga Scleropages jardinii (C); Asian arowana Scleropages formosus (G); black arowana Osteoglossum ferreirai (K); silver arowana Osteoglossum bicirrhosum (O); Fourth column (D,H,L,P): merged images of both genomic probes and DAPI staining. The common genomic regions are depicted in yellow. Bar = 5 µm.
Figure 5. Comparative genomic hybridization (CGH) in metaphase plates of the southern saratoga Scleropages leichardti. First column (A,E,I,M): DAPI images (blue); Second column (B,F,J,N): hybridization pattern using Scleropages leichardti gDNA probe (red); Third column (C,G,K,O): hybridization pattern using the gDNA (green) of the northern saratoga Scleropages jardinii (C); Asian arowana Scleropages formosus (G); black arowana Osteoglossum ferreirai (K); silver arowana Osteoglossum bicirrhosum (O); Fourth column (D,H,L,P): merged images of both genomic probes and DAPI staining. The common genomic regions are depicted in yellow. Bar = 5 µm.
Ijms 20 04296 g005
Figure 6. Zoo-FISH experiments with OFE-1 (arrows) and SFO-A (arrowheads) painting probes applied on the metaphase plate of the black arowana Osteoglossum ferreirai (A), silver arowana Osteoglossum bicirrhosum (B); Asian arowana Scleropages formosus that carries the conspicuous heterochromatic block in both (C1) or just one (C2) homologs; the Northern saratoga Scleropages jardinii (D) and Southern saratoga Scleropages leichardti (E). Bar = 5 µm.
Figure 6. Zoo-FISH experiments with OFE-1 (arrows) and SFO-A (arrowheads) painting probes applied on the metaphase plate of the black arowana Osteoglossum ferreirai (A), silver arowana Osteoglossum bicirrhosum (B); Asian arowana Scleropages formosus that carries the conspicuous heterochromatic block in both (C1) or just one (C2) homologs; the Northern saratoga Scleropages jardinii (D) and Southern saratoga Scleropages leichardti (E). Bar = 5 µm.
Ijms 20 04296 g006
Table 1. Collection sites of the Arowana species analyzed, with the sample sizes (N).
Table 1. Collection sites of the Arowana species analyzed, with the sample sizes (N).
SpeciesSampling SiteN
Osteoglossum bicirrhosumConfusão Lake, Araguaia River. (12♀ 11♂)
Osteoglossum bicirrhosumCatalão Lake, Solimões River (12♀ 11♂)
Osteoglossum ferreiraiNegro River (Amazon River Basin)(15♀ 19♂)
Scleropages formosus (Super Red variety)Origin unknown, Aquarium trade(03♀ 02♂)
Scleropages jardiniiCorroboree Billabong, Mary River(05♀ 03♂)
Scleropages leichardtiFitzroy River via aquarium trade(03♀ 04♂)

Share and Cite

MDPI and ACS Style

de Bello Cioffi, M.; Ráb, P.; Ezaz, T.; Antonio Carlos Bertollo, L.; Lavoué, S.; Aguiar de Oliveira, E.; Sember, A.; Franco Molina, W.; Henrique Santos de Souza, F.; Majtánová, Z.; et al. Deciphering the Evolutionary History of Arowana Fishes (Teleostei, Osteoglossiformes, Osteoglossidae): Insight from Comparative Cytogenomics. Int. J. Mol. Sci. 2019, 20, 4296.

AMA Style

de Bello Cioffi M, Ráb P, Ezaz T, Antonio Carlos Bertollo L, Lavoué S, Aguiar de Oliveira E, Sember A, Franco Molina W, Henrique Santos de Souza F, Majtánová Z, et al. Deciphering the Evolutionary History of Arowana Fishes (Teleostei, Osteoglossiformes, Osteoglossidae): Insight from Comparative Cytogenomics. International Journal of Molecular Sciences. 2019; 20(17):4296.

Chicago/Turabian Style

de Bello Cioffi, Marcelo, Petr Ráb, Tariq Ezaz, Luiz Antonio Carlos Bertollo, Sebastien Lavoué, Ezequiel Aguiar de Oliveira, Alexandr Sember, Wagner Franco Molina, Fernando Henrique Santos de Souza, Zuzana Majtánová, and et al. 2019. "Deciphering the Evolutionary History of Arowana Fishes (Teleostei, Osteoglossiformes, Osteoglossidae): Insight from Comparative Cytogenomics" International Journal of Molecular Sciences 20, no. 17: 4296.

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop