Fish Genus Research Articles

Molecular evidence reveals fish-pathogenic Aphanomyces spp. (Oomycetes: Saprolegniales) on new host of the threatened seasonal cyprinodont fish Nothobranchius spp. (Teleostei: Cyprinodontiformes) in south-eastern Democratic Republic of Congo

The Aphanomyces species pose an important global threat and cause damage to aquaculture and agriculture by infecting aquatic animals and plants. Several subpopulations of the seasonal cyprinodont fish genus Nothobranchius with lesions suggestive of infection with Aphanomyces invadans, were observed in ephemeral wetland habitats of the upper Congo drainage in the south-eastern Democratic Republic of Congo. Molecular analyses on samples collected in 2023 revealed evidence of fish-pathogenic oomycetes Aphanomyces invadans and A. laevis, for the first time in the host of fish genus Nothobranchius spp. All Nothobranchius fishes in the upper Congo drainage are subject to a high level of threat and belong to one of the threatened Red List categories, due to habitat degradation of seasonal wetlands. These fishes complete their seasonal life cycle in ephemeral natural habitats. The latter makes them highly vulnerable, as such wetland habitats are often degraded by the cumulative effect of multiple human stressors which include: the cultivation of wetlands for agriculture, the abstraction of water, the expansion of urban areas and the pollution load. Evidence of infection by oomycete pathogens documented in this study, represents a critical additional threat to the unique seasonal aquatic biodiversity of the region.

Northward migration past the nearctic biogeographical divide; neotropical Gyrodactylus spp. infecting Astyanax have crossed the Trans-Mexican Volcanic Belt

The neotropical fish genus Astyanax (Characidae) and its associated helminths migrated northward from South America following the Great American Biotic Interchange (GABI): ca. 150 Astyanax spp. are found throughout South and Central America, up to the Mexico-USA border. Most characids are distributed south of the Trans-Mexican Volcanic Belt (TMVB), which bisects the country and represents a major transition zone between the neotropical and nearctic realms. Here, we characterize parasites of the monogenean genus Gyrodactylus infecting Astyanax spp. in Mexico: Astyanax aeneus south of the TMBV, Astyanax mexicanus north of it. Based on morphological, phylogenetic (internal transcribed spacer (ITS) and cytochrome oxidase subunit II (cox 2)) and statistical analyses of morphometric data, we confirmed the validity of Gyrodactylus pakan and Gyrodactylus teken, and erected two new species, Gyrodactylus aphaa n. sp. and Gyrodactylus ricardoi n. sp. These four gyrodactylids are part of a complex of morphologically cryptic species, which are phylogenetically closely related to each other, and sister species to Gyrodactylus carolinae and Gyrodactylus heteracanthus, parasites of characins in Brazil. Four gyrodactylid lineages (G. pakan, G. ricardoi n. sp., G. teken, Gyrodactylus sp. A) are distributed north of the TMVB; G. pakan is also widely distributed south of the TMVB, together with G. aphaa n. sp. Based on the ITS phylogeny, Brazilian parasites form a sister clade to all Mexican gyrodactylids, whose derived clades are distributed in progressively more northerly latitudes in Mexico – the three most-derived species north of the TMVB. This would suggest that gyrodactylid species diverged gradually, presumably as their characid fish hosts colonized and adapted to new environments north of the TMVB.

Comparative analysis reveals assortative mate preferences in darters independent of sympatry and sex.

A preference for mating with conspecifics over heterospecifics is fundamental to the maintenance of species diversity in sexually reproducing organisms. This type of positive assortative preference results in sexual isolation, and a reduction in gene flow between species due to differences in mate choice. The proximate and ultimate causes of sexual isolation therefore constitute active areas of research in evolutionary biology. Sexual isolation is often stronger between closely related sympatric species as compared to allopatric species because of processes such as reinforcement. In addition, traditional theories of sexual selection suggest that because reproduction is more costly to females, they should be the choosier sex and play a more central role in sexual isolation. We conducted a comparative analysis of assortative mate preferences in males and females of sympatric and allopatric species pairs of darters (fish genus Etheostoma). We performed a meta-analysis of 17 studies, encompassing 21 species, in which assortative preference was measured when fish were (in most cases) allowed only visual information. As expected, we found stronger preferences for conspecifics over heterospecifics across studies and species. However, we did not find an effect of sympatry or sex on the strength of preference for conspecifics, but rather remarkable variation across species. We offer several testable hypotheses to explain the variation we observed in the strength of assortative preference.

Taxonomic Diversity and Interannual Variation of Fish in the Lagoon of Meiji Reef (Mischief Reef), South China Sea.

Coral reef fish are important groups of coral reefs, which have great economic and ecological value. Meiji Reef is a representative tropical semi-enclosed atoll in the South China Sea, with rich fish resources. Based on the data from hand-fishing, line-fishing, and gillnet surveys of fish in Meiji Reef from 1998 to 2018, this study summarized the fish species list of Meiji Reef and analyzed the species composition, inclusion index at the taxonomic level (TINCL), genus-family diversity index (G-F index), average taxonomic distinctness index (Δ+), and variation in taxonomic distinctness (Λ+) and their changes. The results revealed that from 1998 to 2018, there were 166 reef-dwelling fish species on Meiji Reef, belonging to 69 genera, 33 families, and 11 orders, of which 128 species were from 20 families of Perciformes, accounting for 77.10% of the total cataloged species. Regarding the dependence of fish on coral reefs, there were 155 reef-dependent species or resident species (accounting for 93.37%) and 11 reef-independent species or wandering species (accounting for 6.63%). The TINCL of the order, families, and genus of fish in Meiji Reef were very high. The genus diversity index (G index), family diversity index (F index), and G-F index of fish in Meiji Reef were very high, and the G index of fish in Meiji Reef in 1998-1999 was higher than that in 2016-2018. The Δ+ and Λ+ values of fish in Meiji Reef from 1998 to 2018 were 56.1 and 148.5, respectively. Compared with 1998-1999, Δ+ and Λ+ of fish increased during 2016-2018, reflecting that the relatives of fish in Meiji Reef became further distant, and the uniformity of taxonomic relationships among species decreased. The research findings indicated that fish exhibited a high taxonomic diversity in Meiji Reef; however, it also revealed significant fluctuations in the fish diversity of Meiji Reef over an extended period, emphasizing the urgent need for timely protection measures. This investigation significantly contributes to our comprehension of the intricate dynamics governing fish species within Meiji Reef and holds broader implications for biodiversity conservation in tropical marine ecosystems.

Genetic variability of Myxobolus nagaraensis (Bivalvulida: Myxobolidae) infecting freshwater gobies Rhinogobius Gill 1859 (Gobiiformes: Oxudercidae) from rivers in Japan

Myxobolus nagaraensis is a myxozoan parasite first reported in freshwater gobies (Rhinogobius spp.) from the Nagara River, Gifu Prefecture, Japan. Myxospores of M. nagaraensis form plasmodia in the visceral cavities of gobies, commonly presenting as distended abdomens. Although Rhinogobius is a common fish genus in Japan, details of M. nagaraensis, including genetic information, remain unknown. We compared the nucleotide sequences of the ribosomal RNA gene (rDNA) of M. nagaraensis from three different host species (R. fluviatilis, R. nagoyae, and R. similis) caught in three different rivers in Japan (Sakai, Sagami, and Kaname). The ITS region (ITS-1, 5.8S rDNA, and ITS-2) and large subunit (LSU) rDNA exhibited 49 and 55 variable sites, respectively. The highest nucleotide diversity was observed in the ITS region (0.00962), whereas that of the LSU rDNA was 0.00187. Differences in host species, rather than rivers, were a significant factor for genetic variation in both the ITS region (62.58%; P < 0.001) and LSU rDNA (55.22%; P < 0.01). Significant genetic variation was observed in M. nagaraensis from R. similis compared to R. fluviatilis (P < 0.001) or R. nagoyae (P < 0.001) from the same river. Such details are valuable for understanding parasite dispersal and its ecological impact on Rhinogobius hosts.

Multi-method survey rediscovers critically endangered species and strengthens Madagascar's freshwater fish conservation

Freshwater ecosystems are crucial for global biodiversity through supporting plant and animal species and providing essential resources. These ecosystems are under significant threat, particularly in island environments such as Madagascar. Our study focuses on the Amboaboa River basin, home to the rare and endemic fish species Rheocles derhami, last recorded in 2013. To assess the status of this and other threatened fish species including Ptychochromis insolitus and Paretroplus gymnopreopercularis, and to understand freshwater fish population dynamics in this biodiversity hotspot, we conducted a comprehensive survey using both environmental DNA (eDNA) and traditional fishing methods. While traditional methods effectively captured a diverse range of species, including several invasive aliens and the critically endangered endemic species that were the focus of this study, the eDNA approach detected only a fraction of these introduced species and struggled to identify some critically endangered endemics at the species level. This highlights the value of combining methods to enhance species detection. We also investigated the trade-offs associated with multi-primer assessments in eDNA analysis, focusing on three different primer combinations targeting the 12S mitochondrial gene: MiFish, Tele02, and Riaz. Additionally, we provided 12S reference barcodes for 10 species across 9 genera of fishes from the region to increase the coverage of the public reference databases. Overall, our study elucidates the current state of freshwater biodiversity in the Amboaboa River basin and underscores the value of employing multiple methods for effective conservation strategies.

New Findings Relating to Bone Processing from Chernyatino-2, Primorye

The article provides a detailed account of faunal materials from the Chernyatino-2 settlement in Russian Primorye. For the first time, a large series of bone blanks from a Bohai (698–926 AD) site is described, enabling us to reconstruct bone-processing techniques and types of tools used, expanding our knowledge of bone-working craft of that region. A detailed classification of bone and antler artifacts of domestic manufacture is presented. Certain artifacts are quite unusual. There are items relating to winter movement and hitherto unknown musical instruments, extending our knowledge of medieval Far Eastern musical culture. Also, we detail the species composition and proportion of domestic and wild animals. Predominant families and genera of fish are listed. The findings are discussed with reference to the role of environment in medieval subsistence strategy.

Integrative taxonomy of the featherback fish genus Chitala (Osteoglossomorpha: Notopteridae) in Peninsular Malaysia

AbstractThe taxonomy of the freshwater featherback fish genus Chitala (Osteoglossomorpha: Notopteridae) remains unsettled because delimiting and naming Chitala species based solely on morphology led to different hypotheses. In this study, we aim to determine the number and identity of Chitala species present in Peninsular Malaysia by employing an integrative taxonomic approach that combines morphology and two mitochondrial markers: the cytochrome c oxidase subunit I (COI) and cytochrome b genes. A total of 60 specimens of Chitala were collected throughout Peninsular Malaysia. Initially, all specimens were sorted into three distinct categories based on their body marking patterns. A molecular phylogenetic analysis revealed that each of these groups was monophyletic, and an automated species partition method further recognized them as distinct species. These results support the presence of three Chitala species in Peninsular Malaysia, even though a multivariate morphometric analysis failed to fully differentiate each of these three species. Comparison with original species descriptions and genetic data from an additional 70 Chitala specimens from neighbouring regions allowed us to name these species as Chitala lopis, Chitala borneensis, and Chitala ornata. We also showed the presence of two undescribed species in Indonesia.

A new species of the fossil pufferfish genus †Archaeotetraodon (Tetraodontidae) from the Middle Miocene of the North Caucasus, Russia

The fossil puffer fish genus †Archaeotetraodon Tyler &amp; Bannikov, 1994 is unique among the Tetraodontidae in having the upright central spinule of the dermal scale plates bifid rather than singular and undivided. Six species of this genus have previously been described variously from the Oligocene and Miocene of Russia, Italy, Algeria, and Ukraine. Described herein is a seventh species of this genus, †Archaeotetraodon bemisae sp. nov., based upon two specimens from the Pshekha River, Krasnodar Region, North Caucasus, Russia. These Maikopian specimens are no less than 15 mya, in the basal-most Middle Miocene. The new species is distinguished from the other six species in the genus by the following combination of characters: thick, sturdy, and smooth bifid spinules; frontal width broad over the orbit; 18 vertebrae; slender ventral postcleithrum; a moderately long rayless pterygiophore; height/length ratio of the posteriormost abdominal centrum being 0.78–0.79; 10 dorsal-fin rays; 9 anal-fin rays; and 14 pectoral-fin rays.

Wall-following - Phylogenetic context of an enhanced behaviour in stygomorphic Sinocyclocheilus (Cypriniformes: Cyprinidae) cavefishes.

With 75 known species, the freshwater fish genus Sinocyclocheilus is the largest cavefish radiation in the world and shows multiple adaptations for cave-dwelling (stygomorphic adaptations), which include a range of traits such as eye degeneration (normal-eyed, micro-eyed and eyeless), depigmentation of skin, and in some species, the presence of "horns". Their behavioural adaptations to subterranean environments, however, are poorly understood. Wall-following (WF) behaviour, where an organism remains in close contact with the boundary demarcating its habitat when in the dark, is a peculiar behaviour observed in a wide range of animals and is enhanced in cave dwellers. Hence, we hypothesise that wall-following is also present in Sinocyclocheilus, possibly enhanced in eyeless species compared to eye bearing (normal-/micro-eyed species). Using 13 species representative of Sinocyclocheilus radiation and eye morphs, we designed a series of assays, based on pre-existing methods for Astyanax mexicanus behavioural experiments, to examine wall-following behaviour under three conditions. Our results indicate that eyeless species exhibit significantly enhanced intensities of WF compared to normal-eyed species, with micro-eyed forms demonstrating intermediate intensities in the WF distance. Using a mtDNA based dated phylogeny (chronogram with four clades A-D), we traced the degree of WF of these forms to outline common patterns. We show that the intensity of WF behaviour is higher in the subterranean clades compared to clades dominated by normal-eyed free-living species. We also found that eyeless species are highly sensitive to vibrations, whereas normal-eyed species are the least sensitive. Since WF behaviour is presented to some degree in all Sinocyclocheilus species, and given that these fishes evolved in the late Miocene, we identify this behaviour as being ancestral with WF enhancement related to cave occupation. Results from this diversification-scale study of cavefish behaviour suggest that enhanced wall-following behaviour may be a convergent trait across all stygomorphic lineages.

The role of satellite DNAs in the chromosomal rearrangements and the evolution of the rare XY1Y2 sex system in Harttia (Siluriformes: Loricariidae).

The underlying processes behind the formation, evolution, and long-term maintenance of multiple sex chromosomes have been largely neglected. Among vertebrates, fishes represent the group with the highest diversity of multiple sex chromosome systems and, with six instances, the Neotropical fish genus Harttia stands out by presenting the most remarkable diversity. However, although the origin mechanism of their sex chromosome systems is well discussed, little is known about the importance of some repetitive DNA classes in the differentiation of multiple systems. In this work, by employing a combination of cytogenetic and genomic procedures, we evaluated the satellite DNA composition of H. carvalhoi with a focus on their role in the evolution, structure, and differentiation process of the rare XY1Y2 multiple sex chromosome system. The genome of H. carvalhoi contains a total of 28 satellite DNA families, with the A+T content ranging between 38,1 and 68,1% and the predominant presence of long satellites. The in situ hybridization experiments detected 15 satellite DNAs with positive hybridization signals mainly on centromeric and pericentromeric regions of almost all chromosomes or clustered on a few pairs. Five of them presented clusters on X, Y1, and/or Y2 sex chromosomes which were therefore selected for comparative hybridization in the other three congeneric species. We found several conserved satellites accumulated on sex chromosomes and also in regions that were involved in chromosomal rearrangements. Our results provide a new contribution of satellitome studies in multiple sex chromosome systems in fishes and represent the first satellitome study for a Siluriformes species.

Comparative Analysis of the Systematics and Evolution of the Pampus Genus of Fish (Perciformes: Stromateidae) Based on Osteology, Population Genetics and Complete Mitogenomes.

Pampus is a widespread species of fish in the western Pacific and Indian Oceans that has significant commercial worth. Its evolutionary history and phylogenetics are still poorly understood, and details on its intraspecific taxonomy are debatable, despite some morphological and molecular research. Here, we analyzed this species using skeletal structure data as well as nuclear (S7 gene) and mitochondrial genetic information (COI, D-loop and mitogenomes). We found that the genetic distance between P. argenteus and P. echinogaster was much smaller than that between other Pampus species, and both maximum likelihood and Bayesian phylogenetic trees yielded almost identical tree topologies. An additional and adjacent M repeat was found in the downstream region of the IQM gene cluster of P. argenteus and P. echinogaster, and the trnL2 gene of P. minor was translocated. The genus Pampus experienced early rapid radiation during the Palaeocene with major lineages diversifying within a relatively narrow timescale. Additionally, three different methods were conducted to distinguish the genus Pampus species, proving that P. argenteus and P. echinogaster are the same species, and P. liuorum is speculated to be a valid species. Overall, our study provides new insights not only into the evolutionary history of Pampus but its intraspecific taxonomy as well.

Cytogenetic Analysis of the Fish Genus Carassius Indicates Divergence, Fission, and Segmental Duplication as Drivers of Tandem Repeat and Microchromosome Evolution.

Fishes of the genus Carassius are useful experimental vertebrate models for the study of evolutionary biology and cytogenetics. Carassius demonstrates diverse biological characteristics, such as variation in ploidy levels and chromosome numbers, and presence of microchromosomes. Those Carassius polyploids with ≥150 chromosomes have microchromosomes, but the origin of microchromosomes, especially in European populations, is unknown. We used cytogenetics to study evolution of tandem repeats (U1 and U2 small nuclear DNAs and H3 histone) and microchromosomes in Carassius from the Czech Republic. We tested the hypotheses whether the number of tandem repeats was affected by polyploidization or divergence between species and what mechanism drives evolution of microchromosomes. Tandem repeats were found in tetraploid and hexaploid Carassius gibelio, and tetraploid Carassius auratus and Carassius carassius in conserved numbers, with the exception of U1 small nuclear DNA in C. auratus. This conservation indicates reduction and/or loss in the number of copies per locus in hexaploids and may have occurred by divergence rather than polyploidization. To study the evolution of microchromosomes, we used the whole microchromosome painting probe from hexaploid C. gibelio and hybridized it to tetraploid and hexaploid C. gibelio, and tetraploid C. auratus and C. carassius. Our results revealed variation in the number of microchromosomes in hexaploids and indicated that the evolution of the Carassius karyotype is governed by macrochromosome fissions followed by segmental duplication in pericentromeric areas. These are potential mechanisms responsible for the presence of microchromosomes in Carassius hexaploids. Differential efficacy of one or both of these mechanisms in different tetraploids could ensure variability in chromosome number in polyploids in general.

Evolution of a novel regulatory mechanism of hypoxia inducible factor in hypoxia-tolerant electric fishes

Hypoxia is a significant source of metabolic stress that activates many cellular pathways involved in cellular differentiation, proliferation, and cell death. Hypoxia is also a major component in many human diseases and a known driver of many cancers. Despite the challenges posed by hypoxia, there are animals that display impressive capacity to withstand lethal levels of hypoxia for prolonged periods of time and thus offer a gateway to a more comprehensive understanding of the hypoxic response in vertebrates. The weakly electric fish genus Brachyhypopomus inhabits some of the most challenging aquatic ecosystems in the world, with some species experiencing seasonal anoxia, thus providing a unique system to study the cellular and molecular mechanisms of hypoxia tolerance. In this study, we use closely related species of Brachyhypopomus that display a range of hypoxia tolerances to probe for the underlying molecular mechanisms via hypoxia inducible factors (HIFs)-transcription factors known to coordinate the cellular response to hypoxia in vertebrates. We find that HIF1⍺ from hypoxia tolerant Brachyhypopomus species displays higher transactivation in response to hypoxia than that of intolerant species, when overexpressed in live cells. Moreover, we identified two SUMO-interacting motifs near the oxygen-dependent degradation and transactivation domains of the HIF1⍺ protein that appear to boost transactivation of HIF1, regardless of the genetic background. Together with computational analyses of selection, this shows that evolution of HIF1⍺ are likely to underlie adaptations to hypoxia tolerance in Brachyhypopomus electric fishes, with changes in two SUMO-interacting motifs facilitating the mechanism of this tolerance.

Gene and Allele-Specific Expression Underlying the Electric Signal Divergence in African Weakly Electric Fish.

In the African weakly electric fish genus Campylomormyrus, electric organ discharge signals are strikingly different in shape and duration among closely related species, contribute to prezygotic isolation, and may have triggered an adaptive radiation. We performed mRNA sequencing on electric organs and skeletal muscles (from which the electric organs derive) from 3 species with short (0.4 ms), medium (5 ms), and long (40 ms) electric organ discharges and 2 different cross-species hybrids. We identified 1,444 upregulated genes in electric organ shared by all 5 species/hybrid cohorts, rendering them candidate genes for electric organ-specific properties in Campylomormyrus. We further identified several candidate genes, including KCNJ2 and KLF5, and their upregulation may contribute to increased electric organ discharge duration. Hybrids between a short (Campylomormyrus compressirostris) and a long (Campylomormyrus rhynchophorus) discharging species exhibit electric organ discharges of intermediate duration and showed imbalanced expression of KCNJ2 alleles, pointing toward a cis-regulatory difference at this locus, relative to electric organ discharge duration. KLF5 is a transcription factor potentially balancing potassium channel gene expression, a crucial process for the formation of an electric organ discharge. Unraveling the genetic basis of the species-specific modulation of the electric organ discharge in Campylomormyrus is crucial for understanding the adaptive radiation of this emerging model taxon of ecological (perhaps even sympatric) speciation.

Chondrichthyan fishes from the Middle Eocene Osinovaya Formation of Rostov Region, Russia

ABSTRACT A new chondrichthyan assemblage comprising 27 genera is described from the Middle Eocene Osinovaya Formation of the Bystraya River Basin, Morozovsk District of Rostov Region, in the southern part of European Russia. The Morozovsk assemblage consists of 21 genera and 24 species of shark, 5 genera and species of batoid and a single genus and species of chimaeroid fish (Edaphodon sp.). A composition of the assemblage is characterised by the coexistence of Otodus sokolovi, O. auriculatus, Isurolamna bajarunasi, Macrorhizodus praecursor, Jaekelotodus trigonalis and Brachycarcharias lerichei and indicates the Lutetian age of the deposits (possibly middle – upper Lutetian because of the presence of O. sokolovi together with O. auriculatus). This corresponds to the previous dating of the Osinovaya Formation. Lamniformes (12 taxa) and Myliobatiformes (5 taxa) are dominated in assemblage between elasmobranchs, characterising the inner to middle neritic warm-water environments. The Morozovsk elasmobranch assemblage belongs to the European paleobiogeographic region and shows a great similarity with the previously known coeval assemblages from the Western Europe, as well as with Uzbek assemblages from the adjacent Crimean-Caucasian paleobiogeographic region. Scarce data on chimaeroid fishes show that only the genus Edaphodon is rarely present in shallow-water environments and only in the European paleobiogeographic region.

Updated distribution and morphological variation of the genus Pseudanos in the Río de la Plata basin (Characiformes: Anostomidae).

Pseudanos is a fish genus with cis-Andean distribution in South America. Pseudanos trimaculatus is originally known from the Amazon and Orinoco basins. Three decades ago, a few specimens collected in the Río de la Plata basin were identified as P. trimaculatus, what remained to be confirmed and understood. The aim of this contribution is to analyze these specimens. Consequently, the morphological variation of P. trimaculatus is discussed and updated. Morphometric and meristic data were taken from the specimens and compared with those of the type and non-type specimens of the species. Multivariate analyses of the size-corrected measurements were used to explore the morphological variation. Size-corrected PCA revealed that the specimens collected in the Río de la Plata basin nested with the remaining specimens, being slightly closer to those from the Guaporé, Napo and Uatumã rivers. Measurements such as caudal peduncle depth, body depth, and body width affected more heavily the first components. Cluster analysis did not show well-defined groups based on the hydrogeographic basins. The studied specimens from the Río de la Plata basin are herein confirmed as conspecific with P. trimaculatus. The species is added to the list of fish species shared between the Amazon and Río de la Plata basins.

Phylogeny of the Genera with Oromandibular Discs in the Subfamily Labeoninae (Teleostei: Cyprinidae) with Descriptions of Two New Genera

The aim of this study was to understand the systematic relationships between certain fish genera with oromandibular discs in the Labeoninae. At the same time, this was an opportunity to clarify the taxonomic status of certain species in the genera Ageneiogarra, Garra, Placocheilus, and other taxa distributed in China. Morphological comparison and molecular analysis were used in the study. The results showed that the genera with oromandibular discs had no recent common ancestor and that their oromandibular discs were the result of convergent evolution in different evolutionary lineages. Due to the homogeneity of their habitats, these fish have evolved oromandibular discs with similar appearance and structure. Both morphological and molecular evidence suggests that (1) Placocheilus cryptonemus distributed in the Nu‐Jiang (the Upper Salween River Basin), Yunnan, China, represent a new genus, here described as Pseudoplacocheilus, and (2) Garra micropulvinus occurring in the Panlong‐He (the upper portion of the Lo River, a branch of the Red River Basin) from Wenshan, Yunnan, represents another new genus, here described as Supradiscus.

Genetic mechanism of body size variation in groupers: Insights from phylotranscriptomics.

Animal body size variation is of particular interest in evolutionary biology, but the genetic basis remains largely unknown. Previous studies have shown the presence of two parallel evolutionary genetic clusters within the fish genus Epinephelus with evident divergence in body size, providing an excellent opportunity to investigate the genetic basis of body size variation in vertebrates. Herein, we performed phylotranscriptomic analysis and reconstructed the phylogeny of 13 epinephelids originating from the South China Sea. Two genetic clades with an estimated divergence time of approximately 15.4 million years ago were correlated with large and small body size, respectively. A total of 180 rapidly evolving genes and two positively selected genes were identified between the two groups. Functional enrichment analyses of these candidate genes revealed distinct enrichment categories between the two groups. These pathways and genes may play important roles in body size variation in groupers through complex regulatory networks. Based on our results, we speculate that the ancestors of the two divergent groups of groupers may have adapted to different environments through habitat selection, leading to genetic variations in metabolic patterns, organ development, and lifespan, resulting in body size divergence between the two locally adapted populations. These findings provide important insights into the genetic mechanisms underlying body size variation in groupers and species differentiation.

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Cyprinidae species are the most abundant and widely distributed fish species in the inland waters of Iraq. Cyprinids are complex species, and it is difficult to identify them on the basis of morphology. Thus, the morphological characteristics must be achieved and confirmed by molecular analysis. Twenty specimens of Cyprinion kais Heckel, 1843 (Piscies, Cypriniformes, Cyprinidae) were collected from two localities at Tigris River in the middle of Iraq: five specimens from Al-Tharthar Lake, Saladin Province, and 15 specimens from Al- Zubaydiyah sub-district, Wasit Province. The DNA sequences of C. kais were done using the mitochondrial DNA cytochrome b (cytb) gene. After analysis, the sequences were compared with sequences of other fish genera and species available in GenBank. The barcoding result (DNA sequencing) showed that it fit with C. kais. We conclude the results of the current study confirm that the validity of the morphological diagnosis of C. kais, using DNA sequencing analysis.