Search Results (124)

Fish venom biology reaches far beyond addressing risks of human envenomation. The critical understanding of venom composition and the drivers that modulate it will enable scientists to deliver a span of novel bioresources with multiple potential biotechnological applications. The lesser weever fish (Echiichtys vipera), common in the surf of sandy beaches in Portugal, is a noteworthy case study due to frequent envenomation episodes during summer, albeit the lack of information regarding its venom system and the composition of its venom. We collected about one hundred animals from Costa da Caparica (W Portugal) as beach trawl (arte xávega) by-catch. Histology showed a similar essential microanatomical structure of glands in both venomous spines (dorsal and opercular) and no obvious gender differences. Transversal sections across the spines showed a T-shaped supportive bone structure that harbor masses of large, glandular cells that bear large sacculi. The structure is surrounded by a retractable layer of skin, thicker in the opercular spines comparatively to dorsal. The lack of muscular tissue near the glands and missing venom delivery ducts in the spines suggest that venom secretion in this species is holocrine, i.e., that venom is delivered through rupture of the skin and underlying glandular tissue upon mechanical pressure. Proteomics of the venomous spines (dorsal and opercular) showed a different proteomic signature between males and females, pointing to intersexual variation and suggesting that other biotic and abiotic factors might influence venom composition (maturation stage or geographic distribution). Additionally, protein homology matches performed against known toxins from marine venomous fishes indicated the presence of novel unexplored toxins in this species besides expected cytolysins. Our focus in the future is to identify, isolate and characterize the individual components of this venom. We anticipate new insights on the intraspecific adaptation of fish venom systems to specific ecological needs and advocate for sustainable bioprospecting for novel proteins with high biotechnological potential. Full article

The species limits of Cranoglanis remain controversial despite their relevance to freshwater fish conservation in southern China. We analyzed mitochondrial cytochrome b sequences from 203 individuals representing seven geographic populations across the Pearl, Red, and Nandujiang drainages to test species validity, assess genetic structure, and infer demographic history. Phylogenetic and haplotype network analyses recovered two deeply divergent lineages: a widespread Clade A distributed across all three drainages and a geographically restricted Clade B confined to the middle Xijiang system of the Pearl River Basin. The traditionally recognized Pearl River, Hainan, and Red River nominal taxa all fell within Clade A rather than forming three independent maternal lineages. Within Clade A, differentiation between the Yuanjiang–Red River and Pearl River populations was low, whereas the Nandujiang population showed significant differentiation and extremely low nucleotide diversity. Divergence dating estimated separation between Clades A and B at 4.9183 Ma. Both lineages showed signals consistent with historical demographic expansion. Our results support recognition of two evolutionarily significant units within Cranoglanis and identify the Nandujiang population as a priority for conservation, while the taxonomic status of Clade B requires further testing with nuclear and morphological evidence. Full article

A new species of shoveljaw carp, Scaphesthes zhejiangensis, is described from the Qiantang River basin and three independent rivers in Zhejiang Province, Southeast China. It is distinguished from other Scaphesthes species by the following combination of characteristics: a long, slender body (depth 19.9–22.2% SL); 46–49 lateral-line scales; 15–17 pre-dorsal scales; a short head (depth 66.8–73.3% HL); a wide mouth (width 36.2–45.3% HL); elongated maxillary barbels shorter than one-third of the eye diameter; reduced but visible rostral barbels; a slender, smooth last simple dorsal ray; and the absence of a longitudinal black stripe along the lateral line. Molecular phylogenetic analysis based on the mitochondrial cytochrome b (cyt b) gene supported the monophyly of S. zhejiangensis sp. nov., which formed a clade with S. virgulatum, S. macrolepis, and the S. barbatum species complex. Full article

Leptobotia rotundilobus is a newly described species in the subfamily Leptobotinae (Teleostei: Cypriniformes), which is endemic to China. Research on this recently discovered species is preliminary, characterized by limited baseline data and the absence of a fully sequenced mitochondrial genome. To elucidate the structural features of the mitochondrial genome of L. rotundilobus, we performed whole-genome sequencing using next-generation sequencing technology and analyzed its genomic composition, gene content, and structural variation through genome assembly and bioinformatics. The complete circular sequence, spanning 16,593 bp, comprises 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and a typical control region (D-loop), all arranged in the canonical order. The overall base composition of the genome was determined to be 30.8% adenine (A), 24.4% thymine (T), 28.6% cytosine (C), and 16.2% guanine (G). This A+T bias (55.2%) is consistent with the mitochondrial genomes of other Leptobotia, which may affect secondary structure. The ratio of non-synonymous (Ka) to synonymous substitutions (Ks) of 13 PCGs of 16 Leptobotinae species is far less than 1 (0.012–0.063), indicating strong negative or purifying selection on the mitogenome in these species. Moreover, to investigate the phylogenetic relationships within the subfamily Leptobotinae, particularly within the genus Leptobotia, we constructed multiple phylogenetic trees of the mitogenome and concatenated 13 PCGs of 39 sequences with Sinibotia superciliaris as an outgroup. The phylogentic trees using the maximum likelihood (ML) and Bayesian inference (BI) methods consistently indicate that: (1) after correcting the species identification error, L. rotundilobus is closely related to L. micra; and (2) the species of Leptobotia and Parabotia each form a monophyletic group. This study provides new insights into the taxonomy and phylogenetic relationships of Leptobotinae, with a particular focus on the genus Leptobotia, thereby contributing to the clarification of the systematics, origin, and evolution of Botiidae. Full article

The ponyfish genus Nuchequula is presents taxonomic challenges within Leiognathidae due to morphological complexities and a lack of genomic resources. However, the absence of a complete mitochondrial genome for Nuchequula longicornis has hindered comprehensive phylogenetic comparisons. Here, we employed an integrative approach combining detailed morphology with molecular validation via 16S rRNA gene sequencing to confirm the identity of specimens from the Beibu Gulf. Furthermore, we present the first complete mitogenome of N. longicornis. This circular 16,514 bp molecule exhibits a typical gene order, a moderate AT bias (54.8%), and strong purifying selection across all protein-coding genes. Phylogenomic analysis based on the complete mitogenome reliably resolved the position of N. longicornis within Leiognathidae, contributing to the discussion on the phylogenetic relationships and potential monophyly of Nuchequula and contributing to the understanding of intra-familial relationships. Our study provides an essential mitogenomic resource for N. longicornis and offers insights into mitochondrial evolutionary patterns within this family. Full article

The debate of the validity of Maylandia vs. Metriaclima as a genus for a group of rock-dwelling cichlids (Pseudotropheus zebra complex) in Lake Malawi, Africa, has been argued for more than 25 years. Probably the most important requirement in describing new zoological taxa is Article 13.1.1 of the International Code of Zoological Nomenclature (ICZN, 4th edition). We demonstrate that the description of Maylandia did not meet these requirements. Thus, we maintain that Maylandia remains a nomen nudum. 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

Hongiastoma zhangbuensis sp. nov. is described from a tributary of the upper reach of the Pearl River basin based on the morphological and molecular data. It is distinguished from all known species within the subfamily Acrossocheilinae by having a combination of the following characteristics: a crescent horny sheath on the lower jaw, a less prominent lower lip limited to the corners of the mouth, a serrated posterior edge of the last simple dorsal-ray, 47–50 lateral-line scales, 9 scales above the lateral line, 16–18 circumpeduncular scales, and 16–18 pre-dorsal midline scales. The molecular phylogeny revealed that H. zhangbuensis sp. nov. was a sister taxon to Hongiastomata argentatum, with a genetic distance ranging from 10.49% to 10.68%. Together, they formed a lineage at the base of the Acrossocheilinae clade. Furthermore, the interspecific genetic distances between the new species and those of Onychostoma sensu lato ranged from 9.9 to 13.4%, indicating significant genetic divergence between this new species and all known species within Onychostoma sensu lato. Therefore, both morphological and molecular data support the recognition of this species as new. Full article

Suruga fundicola, one of the few known deep-dwelling gobies, is found in Japan, South Korea, and China. Owing to the limited availability of specimens, little is known about its mitogenome characterization, phylogenetic relationship, and adaptive evolution. In this study, we sequenced four complete mitogenomes using the DNBSEQ platform and Sanger sequencing. The mitogenomes in length ranged from 17,138 to 17,352 bp, primarily due to the variation in the number of long tandem repeat (LTR) sequences within variable region 3 (VR3). Although the gene composition and arrangement of the S. fundicola mitogenome are largely consistent with those of other gobies, we identified an expansion of the ND2 gene (78 bp), and an unexpected noncoding region (NC, 35 bp) located between the ND2 and tRNA^trp genes. To further investigate the variation in VR3, we sequenced this region in all nineteen individuals with the Sanger sequencing method. We detected eight distinct LTR types, containing one–three mutation sites, which formed ten different VR3 patterns. Most VR3 patterns (14/19) consisted of a single type of pure LTR, while the remaining five exhibited heterogeneous patterns composed of two different LTRs. Notably, in LTR types T1 and T3, which co-occur in heterogeneous patterns P1 and P9, we found their respective pure patterns (P2–3 and P7). Recombination provides a better, more plausible mechanism for generating the heterogeneity patterns than slipped-strand mispairing, which better explains the homogeneous LTR expansions. These findings provide evidence of recombination in the control region of a vertebrate mitogenome. A phylogenetic analysis confirmed that S. fundicola has a close relationship with Am. hexanema and C. stigmatias. Compared to five shallow-water species of the AcanthogobiusGroup, the deep-dwelling goby S. fundicola was found to be under stronger purifying selection. Within its mitochondrial protein-coding genes (PCGs), ND2 and ND6 genes were subject to stronger purifying selection than the others. Additionally, four genes showed signs of selection sites with high credibility (one in ATP6, ND3, and ND4; eight in ND2). This study provides valuable genomic resources for S. fundicola and enhances our understanding of the phylogenetic relationship, mitogenome recombination, and adaptive evolution of the goby. Full article

Background/Objectives: Liobagrus huaiheensis, an endemic fish in the Huaihe River basin, is a newly described species with limited molecular genetic research, hindering understanding of its evolutionary status, population structure, and genetic diversity. This study aimed to characterize its complete mitochondrial genome, clarify its phylogenetic position within Liobagrus, and assess its population genetic diversity. Methods: We obtained the complete mitogenome of L. huaiheensis (sourced from the Zhugan River) through sequencing, followed by detailed annotation of this genomic sequence. We analyzed its genomic structure, nucleotide composition, codon usage, and base asymmetry. Selection pressure on 13 protein-coding genes (PCGs) was evaluated using Ka/Ks ratios. Phylogenetic trees were generated by means of Bayesian inference (BI) and maximum likelihood (ML), using a dataset composed of 13 protein-coding genes (PCGs) from 37 species. Population genetic diversity was assessed using the cox1 gene. Results: The mitogenome is a 16,512 bp circular molecule encoding 37 genes and one control region, with a conserved structure typical of Liobagrus. It has high A + T content (55.74%) with A-preference and C-enrichment. All PCGs undergo purifying selection (Ka/Ks < 1). Phylogenetic analyses revealed L. huaiheensis is closest to L. obesus (100% support), with Liobagrus divided into three clades. The cox1 gene analysis showed low diversity (Hd = 0.656, π = 0.00171) and neutral evolution. Conclusions: This study fills the mitogenome data gap for L. huaiheensis, clarifies its evolutionary characteristics and phylogenetic position, and provides a basis for conservation genetics of Huaihe endemic fishes and molecular evolution research on Amblycipitidae. Full article

Hainania Koller (Teleostei, Cypriniformes, Xenocyprididae) is known as a monotypic genus of sharpbelly fish that is endemic to Hainan Island, China. We describe Ha. minzhengi sp. nov., the second species of Hainania collected from Guangdong, based on morphology and molecular evidence. Phylogenetic relationships were inferred based on the mitochondrial cytochrome b (Cyt b) gene and cytochrome oxidase subunit 1 (COI) gene, by maximum likelihood and Bayesian methods and different partitioning schemes. Our result supports the sister group relationship between Ha. serrata and Ha. minzhengi sp. nov., but the monophyly of Pseudohemiculter or Hemiculterella was not recovered. A diagnostic key to Chinese species of Hainania and Pseudohemiculter is provided. Full article

The common two-banded seabream, Diplodus vulgaris, is a commercially important fish in the Mediterranean and eastern Atlantic, yet its myxosporean parasite diversity remains unknown. To address this gap, we conducted a myxosporean survey in D. vulgaris specimens from eastern Atlantic fishing stocks. Myxospores resembling Kentmoseria were observed in the urinary bladder of three specimens. 18S rDNA analyses, however, identified two isolates as Bipteria lusitanica, with the third also showing the highest similarity to this species. Morphological comparison revealed significant overlap between B. lusitanica and Kentmoseria, particularly in the suture line orientation. Accordingly, we describe a novel species, Kentmoseria sirinensis n. sp., and propose Kentmoseria lusitanica n. comb. The unclear boundaries between Bipteria and Kentmoseria are highlighted, though redefining or suppressing either genus remains premature without sequencing their type species. Moreover, our phylogenetic analyses show these species clustering among Sinuolineidae, rather than Ortholineidae, supporting the dismantling of Ortholineidae and the placement of Kentmoseria within Sinuolineidae. The ancestral placement of Bipteria vetusta suggests that it is taxonomically distinct and not a member of the Sinuolineidae. Finally, the occurrence of two Kentmoseria spp. in D. vulgaris suggests diversification in Diplodus, underscoring the need to study myxosporean diversity in wild stocks to assess aquaculture risks. Full article

Two new miniature tetra species of the genus Priocharax Weitzman and Vari 1987 are described, raising the known species diversity to twelve. Priocharax is characterized by several paedomorphic features such as reductions in the laterosensory system, number of fin rays, ossification of parts of the skull and the presence of a larval rayless pectoral fin in adults. The species described are found in the Rio Purus and Solimões drainages, in the state of Amazonas, Brazil and are diagnosed among themselves and from other species of the genus by the combination of meristic and osteological characters. Furthermore, the two species differ in overall body shape, with one having a deeper body and the other a more streamlined form. Sexual dimorphism was observed in both species. Molecular species delimitation analyses support the distinctiveness of these species. Similarly to Priocharax britzi and to P. conwayi, the specimens analyzed here were collected within and around protected areas, highlighting the importance of these areas for conservation and biodiversity knowledge. Full article

Growth is the most influential aspect in demographic species analysis. Collecting data on ages and sizes (such as length and weight) is a fundamental step in growth modeling, particularly in fishery science. Residual analysis plays a crucial role in parameterizing the mathematical models chosen to describe the growth patterns of the species under investigation. Using optimal residual criteria is essential to improving model performance and accuracy. In the present study, the length-at-age data of the Gulf corvina (Cynoscion othonopterus) were evaluated with the Schnute model to obtain the best error type and to establish the most accurate growth pattern. Later, the observed, constant, depensatory, and compensatory variance approaches were tested using the logistic model. The Bayesian information criterion (BIC) was used as the goodness-of-fit test to obtain the best variance approach parametrizing the growth model. The BIC values selected the observed variance as the best approach to parametrize the logistic growth model. The conclusion is that the observed variance approach produces robust results—that is, the observed variance produced the most plausible fits. It is suggested that the observed error structure should be used to estimate individual growth. Full article

The wolf fish Hoplias malabaricus is a Neotropical species characterized by remarkable karyotypic diversity, including seven karyomorphs (KarA-G) with distinct sex chromosome systems. This study investigated the homologous XY (KarF) and XY₁Y₂ (KarG) sex chromosome systems present in this species by integrating cytogenetics and genomics to examine sex chromosomes’ composition through characterization of repeatome (satellite DNA and transposable elements) and sex-linked markers. Our analysis indicated that both karyomorphs are little differentiated in their sex chromosomes content revealed by satDNA mapping and putative sex-linked markers. Both repeatomes were mostly composed of transposable elements, but neither intra- (male versus female) nor interspecific (KarF x KarG) variations were found. In both systems, we demonstrated the occurrence of sex-specific sequences probably located on the non-recombining region of the Y chromosome supported by the accumulation of sex-specific haplotypes of HmfSat10-28/HmgSat31-28. This investigation offered valuable insights by highlighting the composition of homologous XY and XY₁Y₂ multiple sex chromosomes. Although homologous, the large Y chromosome in KarF corresponds to two separate linkage groups (Y₁ and Y₂) in KarG implying a specific meiotic arrangement involving the X chromosome in a meiotic trivalent chain. This scenario likely influenced recombination rates and, as a result, the genomic composition of these chromosomes. Full article