Search Results (13)

Introduction: Squalius palaciosi (Doadrio, 1980; Leuciscidae) is a highly threatened freshwater fish species with an extremely restricted distribution, currently confined to a few tributaries on the right bank of the Guadalquivir River basin. During the 1980s, its populations were abundant and constituted a dominant component of local fish communities. However, multiple threats led to a drastic population decline, bringing the species to the brink of extinction. From an evolutionary perspective, S. palaciosi is particularly remarkable due to its polyploid condition and its potential involvement in hybridogenetic complexes, a rare phenomenon in the Iberian Peninsula. Hybridogenetic systems are well documented in its congeners Squalius alburnoides, widely distributed across Iberian river basins, and Squalius sp., restricted to the Guadiana basin. In these systems, the maternal lineage is shared (Squalius pyrenaicus), whereas the paternal lineage varies and remains unknown in S. palaciosi. Objective: This study aims to generate the first genomic data for S. palaciosi and to elucidate its evolutionary origin, as well as its mitochondrial and nuclear phylogenetic relationships within hybridogenetic complexes. Methodology: Genomic DNA was extracted from skeletal remains of preserved specimens housed in the fish collection of the National Museum of Natural Sciences (MNCN-CSIC) and subjected to Illumina short-read sequencing. After quality filtering, potential contaminant reads were removed. The complete mitochondrial genome and several nuclear gene fragments were assembled. Mitochondrial phylogenetic analyses were conducted using publicly available whole-genome sequencing data from Iberian freshwater fish species. Nuclear gene fragments were taxonomically assigned using BLAST analyses. Results: Phylogenetic analyses revealed that S. palaciosi is closely related at the mitochondrial level to S. alburnoides and S. tartessicus, with strong statistical support. BLAST-based taxonomic assignments of nuclear markers suggest the involvement of multiple Iberian freshwater fish species in the hybridogenetic origin of S. palaciosi. Conclusions: Our results provide novel insights into the evolutionary history of S. palaciosi and support a complex hybridogenetic origin involving multiple parental lineages. This study contributes to a better understanding of hybridogenetic speciation in freshwater fishes, a rare but evolutionarily significant process. Full article

Introduction: Studying the structure and dynamics of living communities is essential from both ecological and wildlife management perspectives. Objective: The main objective of this study was to analyze the fish community structure inhabiting different river sections across several basins in the Mediterranean area. The data collected here contributed to: (i) creating a regional and national reference inventory to assess ichthyological biodiversity; (ii) generating digital cartographic information on species distribution and potential habitats; and (iii) providing scientific data to update national legal protection for governments. Methodology: Fish assemblages were monitored using electrofishing, which ensures reproducible data and long-term comparability. The study period extended until autumn 2025, with intensive sampling at 30 sites across major water bodies in the Valencian Community and selected rivers in Mijares, Turia, Jucar and Palancia basins. Results: The results reveal notable ichthyological richness in the studied basins (Turia, Júcar, Palancia, Mijares), with 12 native species identified. Cyprinidae and Leuciscidae were the most representative families, both in species number and spatial distribution, consistent with their dominance in Mediterranean river systems. Areas with the highest species richness corresponded to the middle and lower river sections and to ecologically valuable coastal wetlands. However, the study also detected 10 invasive alien species, representing 45% of the total fish fauna recorded. This high proportion reflects the significant ecological alteration affecting rivers and wetlands in these basins and underscores the urgent need for management actions to limit the spread of invasive species and reduce their impact on native biodiversity. The most widespread IAS were the bleak (A. alburnus), mainly in the Júcar basin, and the mosquitofish (G. holbrooki), predominantly in coastal wetlands. Conclusions: This study contributes directly to updating the Atlas of Ichthyofauna of the Valencian Community, providing a robust and current information base to support environmental decision-making at regional and national levels. The findings highlight the importance of strengthening proactive conservation measures, particularly in areas where biodiversity is most vulnerable. Full article

Background: Phoxinus grumi, a small leuciscid fish endemic to the Turpan Basin in Xinjiang, China, has long been the subject of taxonomic disputes, hindering accurate species identification and the understanding of its evolutionary history. Methods: To resolve this uncertainty, we sequenced and characterized the complete mitochondrial genome of P. grumi using next-generation sequencing. Results: The circular mitogenome is 16,604 bp long and comprises the typical 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and one control region, exhibiting gene overlap and intergenic spacing. The overall base composition shows a pronounced AT bias. Notably, all tRNA genes except tRNA-Ser1 fold into a typical cloverleaf secondary structure; tRNA-Ser1 lacks the dihydrouracil (DHU) arm, representing an unusual structural variation. All 13 PCGs have been subject to purifying selection (Ka/Ks < 1), with ATP8 evolving fastest and COX1 being the most conserved. Maximum likelihood (ML) and Bayesian inference (BI) phylogenetic analyses were conducted based on the concatenated sequences of the 13 mitochondrial PCGs, as well as the Cytb gene. Both datasets consistently placed P. grumi within the subfamily Pseudaspininae, forming a strongly supported sister relationship with the genus Rhynchocypris. This inference was further supported by Kimura two-parameter (K2P) genetic distance analyses, which revealed the smallest divergence between P. grumi and Rhynchocypris species (0.1620–0.1703), markedly smaller than that observed between P. grumi and core Phoxinus species (0.2475–0.2558). Conclusions: Together, these results support the placement of P. grumi within the East Asian Pseudaspininae lineage and help clarify its taxonomic position, which has long been debated. The complete mitochondrial genome of P. grumi provides additional mitogenomic data for phylogenetic analyses of Leuciscidae and contributes to a better understanding of the evolutionary relationships and diversification of Far Eastern leuciscids. These findings may also provide a molecular basis for future studies on the conservation genetics and environmental adaptation of this endemic cold-water fish from the arid Turpan Basin in northwestern China. Full article

To understand the demography of an evolutionarily naïve fish species that sometimes coexists with an invasive predator, we collected mark–recapture data and size–frequency data of two populations of southern leatherside chub (Lepidomeda aliciae), one of which coexists with nonnative brown trout (Salmo trutta). For each population, we estimated vital rates from mark–recapture data to inform a stage-structured matrix transition model. We also used size–frequency distributions from these populations in an integral projection model. Southern leatherside chub from the predator-free environment exhibited higher survival (except age-0) and lower average realized fecundity than the population from the predator environment. Survival rates of age-0 in the predator environment were double the rates in the predator-free habitat. Growth transitions from the smallest size class and reproduction at medium sizes had a combined elasticity of nearly 0.70 in the predator environment, but only 0.43 in the predator-free population. Our results indicate that the southern leatherside chub in Lost Creek that are sympatric with invasive brown trout have reduced abundance and survival of larger individuals and higher age-0 survival and value of reproduction at smaller sizes, compared to the Salina Creek population. Full article

Hybridization is common among minnows and shiners in the family Leuciscidae, and mitonuclear discordance can reveal evidence of historical hybridization and introgression events that have shaped extant species and populations. We have identified a notable case of serial mitogenome replacement in populations of two shiner species, Luxilus zonatus and L. chrysocephalus, which are syntopic in drainages throughout the northern and eastern Ozark Interior Highlands of North America. These mitogenome replacement events involved L. zonatus acquiring the mitogenome of L. chrysocephalus, and populations of L. chrysocephalus acquiring the mitogenome of an allopatric congeneric species, L. cornutus. The latter species has a more northern distribution that was likely shifted southward by glacial advances during the Pleistocene. The geographic extent of mitogenome replacements in both species spans multiple separate drainages encompassing most of the major river systems that comprise the northern and eastern Ozark Highlands. We attribute these patterns to shifting species distributions, which were impacted by multiple glacial advances and coincident geomorphological changes to Ozark Highland drainages throughout the Pleistocene. The serial nature of mitogenome replacements in L. zonatus and L. chrysocephalus may exclude a role for natural selection in these introgression events, but the dynamic shifts in species distributions and gene flow connections throughout the Pleistocene may have favored an invasion-with-hybridization model that predicts massive asymmetric introgression between invading and resident species. These results have applied significance for eDNA metabarcoding methods of biodiversity assessment in Ozark streams, as they are dependent on mitogenome detections. Full article

Invasive species are often central to conservation efforts, particularly when concerns involve potential impacts on rare, endemic native species. The lower New River drainage of the eastern United States is a watershed that warrants conservation assessment, as the system is naturally depauperate of native fish species and it is nearly saturated with non-native fish species: there are 31 natives, including at least nine endemic taxa, and 63 non-natives. For endemic taxa, we examined temporal distribution shifts (range expansions or contractions) based on percent change in the occupied watershed area. We contrasted these findings with time series analyses on distribution trends of non-native minnows (Leuciscidae) and darters (Percidae) based on growth curve models of the cumulative sum of the total area of occupied 12-digit hydrologic unit codes. We documented range reductions for six of nine endemic taxa. We determined that 11 of 18 non-native minnows and 6 of 8 non-native darters were invasive based on range expansions and associated invasion curve models. The endemic taxa are of conservation concern given the limited distribution ranges and documented population declines. Although among-species comparisons of range shifts do not support causal inference, documentation of changes in distribution ranges of endemic and invasive species is critical to inform conservation efforts. Full article

In the present study, we provide a checklist of the predators that may impact the population of the critically endangered Mandra shemaya (Alburnus mandrensis Drensky, 1943). This endemic fish only inhabits the basin of Mandra Lake in the Burgas district (SE Bulgaria) and data on its biology are scarce. We have confirmed the presence of the Mandra shemaya in Mandra Lake for the last six years (including 2024) and provided an analysis on the potential predatory pressures on A. mandrensis. The recently recorded presence of a highly invasive piscivorous predatory fish in Mandra Lake is considered potentially dangerous for the sustainability of native fish species. Full article

Conservation of indigenous species, especially endemic ones, is of the utmost importance. Morphological determination of species is usually not sufficient; therefore, molecular phylogenetic analyses of the Illyrian chub, Squalius illyricus, and the Zrmanja chub, Squalius zrmanjae, from the Krka River were performed. For the genetic characterization of the mitochondrial gene cytochrome b and the non-coding nuclear region Cyfun P, 15 specimens from each species were subjected to analysis. The obtained sequences were aligned with similar ones from GenBank to determine the taxonomic and phylogenetic position of these species. The obtained molecular results imply that S. zrmanjae from the Krka River has a nuclear region that resembles Dalmatian rudd, Scardinius dergle. This result implies an introgression event and the transfer of genetic information between the two genera. The investigated species are on the IUCN Red List of Threatened Species, their biological data are scarce, and further investigation and protection are needed. Full article

We investigated the Gyrodactylus ectoparasites on relict fishes in the isolated endorheic Central Asian Internal drainage basin in Mongolia (The Hollow) and placed them into the global phylogenetic framework based on internal transcribed spacer regions of the nuclear ribosomal DNA (ITS). Much of the rich Pliocene lacustrine ichthyofauna is extinct. We sampled five riverine survivors: Altai osmans Oreoleuciscus humilis and O. potanini (Leuciscidae), Mongolian grayling Thymallus brevirostris (Salmonidae), and stone loaches Barbatula conilobus and B. cobdonensis (Nemacheilidae). We found eight species of the subgenus Gyrodactylus (Limnonephrotus) and four of G. (Gyrodactylus). Nine species were identified as taxa described earlier, and three were described as new. The endemic Mongolian grayling carried four species, only one of wageneri group typical to salmonids (Gyrodactylus radimi sp. nov.), two of nemachili group (G. zavkhanensis sp. nov., G. pseudonemachili Ergens and Bychowsky, 1967), and G. amurensis Akhmerov, 1952 of subgenus G. (Gyrodactylus). G. pseudonemachili was also found on osman and loach. A parasite clade typical for Nemacheilidae was overrepresented by five species (G. tayshirensis sp. nov. on Barbatula conilobus, G. mongolicus Ergens and Dulmaa, 1970, G. nemachili Bychowsky, 1936). Relaxed host specificity mentioned already by Ergens and Dulmaa was evident. In the updated global ITS phylogenies of the two freshwater-restricted subgenera, the parasites from the Mongolian relict populations assumed positions concordant with a hypothesis of multiple ancient introductions from the Euro-Siberian fauna, strong rarefaction and three cases of endemic divergence. Full article

Italy hosts a large number of endemic freshwater fish species due to complex geological events which promoted genetic differentiation and allopatric speciation. Among them, the South European roach Sarmarutilus rubilio inhabits various freshwater environments in three different ichthyogeographic districts. We investigated the genetic diversity of S. rubilio using two different mitochondrial markers (COI and CR), aiming to define its relationship with other similar taxa from the Balkan area and, from a phylogeographic perspective, test the effects of past hydrogeological dynamics of Italian river basins on its genetic structure and demographic history. Our analysis highlighted a marked genetic divergence between S. rubilio and all other roach species and, among Italian samples, revealed the existence of three deeply divergent geographic haplogroups, named A, B and C. Haplogroup C likely corresponds to a new putative cryptic species and is located at the northern border of the South European roach range; haplogroup B is restricted to Southern Italy; and haplogroup A is widespread across the entire range and in some sites it is in co-occurrence with C or B. Their origin is probably related to the tectonic uplifting of the Apuan Alps in the north and of the Colli Albani Volcano in the south during the Pleistocene, which promoted isolation and vicariance followed by secondary contacts. Full article

This is the first report of the early development for the endemic Krbava minnow Delminichthys krbavensis from a karstic field in Croatia, and the first report of any species of the genus Delminichthys. The description is based on basic morphometric measures and meristic counts during a 48-day observation of embryos and larvae acquired from successful spawning and rearing in an aquarium. The mean total length of larvae at the time of hatching was 3.12 mm. Mouth opening and independent feeding and intestinal function were observed after day 11 post-hatching (PH) at which time the yolk sac was completely absorbed in all individuals. Flexion of the urostyle began after day 18 PH and was completed by day 23 PH. Pectoral fins developed on day 7 PH, pelvic fins begin to develop by day 44 PH and the formation of caudal, dorsal and anal fin was complete by day 48 PH, when individuals presented the full set of soft rays. Understanding its early development is particularly valuable in assessing the environmental impacts on this endangered species and is essential for its effective monitoring and conservation. Full article

Host-specific parasites exhibit close co-evolutionary associations with their hosts. In the case of fragmented/disjunct host distribution, host-specific parasites may reflect the biogeographical history of regions and/or the role played by contacts of hosts. The present study was focused on Dactylogyrus (Monogenea) species almost exclusively parasitizing cyprinoid fishes. We investigated the phylogenetic relationships between Dactylogyrus parasites of Nearctic cyprinoids (Leuciscidae) and Dactylogyrus parasites of Palearctic cyprinoids and used Dactylogyrus phylogeny to explore the biogeography of fish hosts in Europe and North America. Phylogenetic analyses revealed that two Nearctic clades of Dactylogyrus spp. have different origins. Historical contacts between European and North American leuciscids were accompanied by the host switching of Dactylogyrus species. In the Nearctic region, Dactylogyrus parasites also colonized non-leuciscid fishes. Dactylogyrus spp. of three Nearctic leuciscid clades were included in the phylogenetic reconstruction; only Dactylogyrus spp. of the Plagopterinae had a common origin. Dactylogyrus species did not reflect the phylogenetic relationships among leuciscid clades, suggesting that past co-diversification was overshadowed by colonization events mediated by paleogeographic and climatological changes and extensive drainage reorganization. Host-specific monogeneans serve as a supplementary tool to reveal the historical biogeographical contacts between freshwater fish from the North America and Europe and also contemporary contacts of leuciscids in North America. Full article

Supernumerary B chromosomes (Bs) are very promising structures, among others, in that they are an additional genomic compartment for evolution. In this study, we tested the presence and frequency of B chromosomes and performed the first cytogenetic examination of the common nase (Chondrostoma nasus). We investigated the individuals from two populations in the Vistula River basin, in Poland, according to the chromosomal distribution of the C-bands and silver nucleolar organizer regions (Ag-NORs), using sequential staining with AgNO₃ and chromomycin A₃ (CMA₃). Furthermore, we analyzed the chromosomal localization of two rDNA families (45S and 5S rDNA) using fluorescence in situ hybridization (FISH) with rDNA probes. Chondrostoma nasus individuals showed a standard (A) chromosome set consisting of 2n = 50: 12 metacentric, 32 submetacentric, and 6 acrocentric chromosomes (NF = 94). Fourteen out of the 20 analyzed individuals showed 1–2 mitotically unstable submetacentric B chromosomes of different sizes. Six of them, in 14.1% of the analyzed metaphase plates, had a single, medium-sized submetacentric B (Bsm) chromosome (2n = 51) with a heterochromatic block located in its pericentromeric region. The other seven individuals possessed a Bsm (2n = 51) in 19.4% of the analyzed metaphase plates, and a second Bsm chromosome (2n = 52), the smallest in the set, in 15.5% of metaphase plates, whereas one female was characterized by both Bsm chromosomes (2n = 52) in 14.3% of the analyzed metaphase plates. AgNORs, GC-rich DNA sites, and 28S rDNA hybridization sites were observed in the short arms of two submetacentric chromosome pairs of A set. The constitutive heterochromatin was visible as C bands in the centromeric regions of almost all Chondrostoma nasus chromosomes and in the pericentromeric region of several chromosome pairs. Two 5S rDNA hybridization sites in the pericentromeric position of the largest acrocentric chromosome pair were observed, whereas two other such sites in co-localization on a smaller pair of NOR chromosomes indicate a species-specific character. The results herein broaden our knowledge in the field of B chromosome distribution and molecular cytogenetics of Chondrostoma nasus: a freshwater species from the Leuciscidae family. Full article