Complete mitochondrial DNA sequences of the Nile tilapia (Oreochromis niloticus) and Blue tilapia (Oreochromis aureus): genome characterization and phylogeny applications

Negative Selection in Oreochromis niloticus × O. aureus Hybrids Indicates Incompatible Oxidative Phosphorylation (OXPHOS) Proteins

Crossing Oreochromis niloticus (On) females with O. aureus (Oa) males results in all-male progeny that are essential for effective tilapia aquaculture. However, a reproductive barrier between these species prevents commercial-scale yield. To achieve all-male progeny, the currently used practice is crossing admixed stocks and feeding fry with synthetic androgens. Hybrid tilapias escaping to the wild might impact natural populations. Hybrids competing with wild populations undergo selection for different stressors, e.g., oxygen levels, salinity, and low-temperature tolerance. Forming mitochondrial oxidative phosphorylation (OXPHOS) complexes, mitochondrial (mtDNA) and nuclear DNA (nDNA)-encoded proteins control energy production. Crossbred tilapia have been recorded over 60 years, providing an excellent model for assessing incompatibility between OXPHOS proteins, which are critical for the adaptation of these hybrids. Here, by comparing nonconserved amino acid substitutions, across 116 OXPHOS proteins, between On and Oa, we developed a panel of 13 species-specific probes. Screening 162 SRA experiments, we noted that 39.5% had a hybrid origin with mtDNA-nDNA allele mismatches. Observing that the frequency of interspecific mtDNA-nDNA allele combinations was significantly (p < 10-4) lower than expected for three factors, UQCRC2, ATP5C1, and COX4B, we concluded that these findings likely indicated negative selection, cytonuclear incompatibility, and a reproductive barrier.

Identification and functional characterization of a novel TRPA1 gene from sea cucumber Apostichopus japonicus and interaction with miR-2013 in response to salt stress

Salinity is important abiotic factor influencing sea cucumber aquaculture. This study aimed to identify and functional study of a novel transient receptor potential cation channel subfamily A member 1 (TRPA1) involved in salinity stress through interaction with miR-2013 in the sea cucumber. The full-length cDNA sequence was 1369 bp in length and encoded 138 amino acids. The TRPA1 homolog protein was a hydrophilic protein without a signal peptide and was predicted to a spatial structure of seven helices and eight random coils and two major ANK functional domains. Bioinformatic analysis and luciferase reporter assays confirmed TRPA1 as a target gene of miR-2013. Quantitative PCR revealed that miR-2013 was induced upregulation after salinity stress, while TRPA1 showed upregulated expression with maximum expression at 24 h. The expression of miR-2013 and TRPA1 was negatively regulated. Transfection experiments were conducted to validate the role of miR-2013 and TRPA1 in salinity response. The results showed that miR-2013 was upregulated and TRPA1 was downregulated after transfection with miR-2013 mimics, while miR-2013 was downregulated and TRPA1 was upregulated after transfection with miR-2013 inhibitor. Transfection with si-TRPA1 homolog resulted in upregulation of miR-2013 and downregulation of TRPA1 homolog. These findings suggest that miR-2013 can regulate the expression of TRPA1 under salt stress, and highlight the importance of miR-2013 and TRPA1 in salt stress response. miR-2013 mimics improved the survival rate, while miR-2013 inhibitor and si-TRPA1 reduced it. These findings suggest that miR-2013 and TRPA1 play important roles in sea cucumbers adaptation to salinity changes.

Mitogenomic Characterization of Cameroonian Endemic Coptodon camerunensis (Cichliformes: Cichlidae) and Matrilineal Phylogeny of Old-World Cichlids

The mitogenomic evolution of old-world cichlids is still largely incomplete in Western Africa. In this present study, the complete mitogenome of the Cameroon endemic cichlid, Coptodon camerunensis, was determined by next-generation sequencing. The mitogenome was 16,557 bp long and encoded with 37 genes (13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and a control region). The C. camerunensis mitogenome is AT-biased (52.63%), as exhibited in its congener, Coptodon zillii (52.76% and 53.04%). The majority of PCGs start with an ATG initiation codon, except COI, which starts with a GTG codon and five PCGs and ends with the TAA termination codon and except seven PCGs with an incomplete termination codon. In C. camerunensis mitogenome, most tRNAs showed classical cloverleaf secondary structures, except tRNA-serine with a lack of DHU stem. Comparative analyses of the conserved blocks of two Coptodonini species control regions revealed that the CSB-II block was longer than other blocks and contained highly variable sites. Using 13 concatenated PCGs, the mitogenome-based Bayesian phylogeny easily distinguished all the examined old-world cichlids. Except for Oreochromini and Coptodinini tribe members, the majority of the taxa exhibited monophyletic clustering within their respective lineages. C. camerunensis clustered closely with Heterotilapia buttikoferi (tribe Heterotilapiini) and had paraphyletic clustering with its congener, C. zillii. The Oreochromini species also displayed paraphyletic grouping, and the genus Oreochromis showed a close relationship with Coptodinini and Heterotilapiini species. In addition, illustrating the known distribution patterns of old-world cichlids, the present study is congruent with the previous hypothesis and proclaims that prehistoric geological evolution plays a key role in the hydroclimate of the African continent during Mesozoic, which simultaneously disperses and/or colonizes cichlids in different ichthyological provinces and Rift Lake systems in Africa. The present study suggests that further mitogenomes of cichlid species are required, especially from western Africa, to understand their unique evolution and adaptation.

On the Species Identification of Two Non-Native Tilapia Species, Including the First Record of a Feral Population of Oreochromis aureus (Steindachner, 1864) in South Korea

Tilapia is an invasive species that has become widely distributed around the world. In Korea, introduced tilapia into its aquatic ecosystem for the first time with a species from Thailand in 1955, and later additionally introduced two more species from Japan and Taiwan, thus securing a total of three species of tilapia (O. niloticus, O. mossambicus and O. aureus) as food resources. Since then, O. niloticus has been reported to inhabit certain streams with thermal effluent outlets. Morphological species identification is very difficult for tilapia and a combined analysis of morphological and molecular-based species identification is therefore necessary. This study investigated a tilapia population that inhabits a thermal effluent stream (Dalseo Stream) in Daegu Metropolitan City, Korea, in order to conduct a morphological and genetic species identification of this population. In total, 37 tilapia individuals were sampled. The results of the morphological and genetic species identification analyses found that two species, O. aureus and O. niloticus, inhabit the Dalseo Stream. In Korea, the habitat of the O. niloticus natural population has been reported, but the O. aureus natural population has not been reported. Thus, we observed for the first time that a new invasive species, O. aureus, inhabits a stream in Korea. They are known to cause disturbances to aquatic organisms (e.g., fish, aquatic insects, plankton, aquatic plants) and the habitat environment (e.g., water quality, bottom structure). Accordingly, it is important to study the ecological effects of O. aureus and O. niloticus on the corresponding freshwater ecosystem closely and to prepare a management plan to prevent the spread of these species, as they are notoriously invasive.

Mitochondrial DNA reveals shallow population genetic structure in economically important Cyprinid fish Labeo rohita (Hamilton, 1822) from South and Southeast Asia

BACKGROUND

Assessment of genetic diversity and population genetic structure is important for species that are economically important, threatened, and are at global conservation priority. Analysis of mitochondrial DNA is broadly used in species identification and population genetics studies due to the availability of sufficient reference data and better evolutionary dynamics for phylogeographic investigation. Labeo rohita (Rohu) is an economically important species cultured under carp polyculture systems in Asia. The present study explores the genetic diversity, phylogeography, and population structure of L. rohita from different countries using cytochrome oxidase subunit I (COI) gene.

METHODS AND RESULTS

A total of 17 L. rohita specimens were sampled from River Beas, India. For the genetic study, we amplified and sequenced COI mitochondrial DNA region. The obtained genetic data was combined with 268 COI records available in the NCBI and BOLD databases originating from multiple populations/countries across South and Southeast Asia. As a result, 33 haplotypes were identified that displayed low nucleotide (π = 0.0233) and moderate haplotype diversity (Hd = 0.523). Tajima (D) was found to be negative (P > 0.05), whereas Fu's Fs showed a positive value (P > 0.05). The overall F_ST value between studied populations was 0.481 (P < 0.05).

CONCLUSION

AMOVA analysis indicated higher variation within than among the population examined. The neutrality tests suggested the presence of rare haplotypes and stable demography within studied populations of L. rohita. The Bayesian skyline plot indicated steady population growth until 1 Mya followed by population decline, whereas F_ST values indicated significant genetic differentiation. High heterogeneity was observed in the Pakistan population which could be indicative of long-term isolation and excessive culturing to meet market demands. The present results are the first global comparative analysis of L. rohita and pave the way forward for detailed genomic and ecological studies aimed at the development of improved stock and effective conservation plans. The study also makes recommendations to conserve the genetic integrity of wild species from aquaculture-reared fishes.

Characterization and phylogenetic analysis of the complete mitochondrial genome of Mango tilapia (Sarotherodon galilaeus: Cichlidae)

BACKGROUND

Sarotherodon galilaeus (Linné, 1758) is a member of the family Cichlidae, which is considered the most important aquaculture freshwater species endemic to Africa and the Middle East. The genetics and molecular biology of this species are rare. This requires more comprehensive mitochondrial genomes-based phylogenetics to enhance understanding of the relationship and delineate this species.

METHODS AND RESULTS

Here, we assembled the complete mitogenome of S. galilaeus using Illumina high-throughput sequencing technology. The mango tilapia mitogenome was 16,631 bp in length with an AT composition of 53.4% and 46.4% GC content. It encodes 37 genes comprising two ribosomal RNA genes (rRNAs), 22 transfer RNA genes (tRNAs), and 13 protein-coding genes (PCGs) as well as the D-loop known as the control region. The phylogenetic tree was conducted to provide a relationship within the haplotilapiine lineage based on the maximum likelihood method, and the newly sequenced S. galilaeus was clustered with other Sarotherodon species.

CONCLUSION

Our results provide a new perception of the genetic basis of S. galilaeus species for further research on systematics, evolution, population genetics, and molecular ecology.

Mitogenomic Features and Evolution of the Nile River Dominant Tilapiine Species (Perciformes: Cichlidae)

To better understand the diversity and evolution of cichlids, we sequenced, assembled, and annotated the complete mitochondrial genomes of three Nile tilapiine species (Coptodon zillii, Oreochromis niloticus, and Sarotherodon galilaeus) dominating the Nile River waters. Our results showed that the general mitogenomic features were conserved among the Nile tilapiine species. The genome length ranged from 16,436 to 16,631 bp and a total of 37 genes were identified (two ribosomal RNA genes (rRNAs), 22 transfer RNA genes (tRNAs), 13 protein-coding genes (PCGs), and 1 control region). The ND6 was the only CDS that presented a negative AT skew and a positive GC skew. The most extended repeat sequences were in the D-loop followed by the pseudogenes (trnS^GCU). The ND5 showed relatively high substitution rates whereas ATP8 had the lowest substitution rate. The codon usage bias displayed a greater quantity of NNA and NNC at the third position and anti-bias against NNG. The phylogenetic relationship based on the complete mitogenomes and CDS was able to differentiate the three species as previously reported. This study provides new insight into the evolutionary connections between various subfamilies within cichlids while providing new molecular data that can be applied to discriminate between Nile tilapiine species and their populations.

Exposure to salinity induces oxidative damage and changes in the expression of genes related to appetite regulation in Nile tilapia (Oreochromis niloticus)

Variations in water salinity and other extrinsic factors have been shown to induce changes in feeding rhythms and growth in fish. However, it is unknown whether appetite-related hormones mediate these changes in Nile tilapia (Oreochromis niloticus), an important species for aquaculture in several countries. This study aimed to evaluate the expression of genes responsible for appetite regulation and genes related to metabolic and physiological changes in tilapia exposed to different salinities. Moreover, the study proposed to sequence and to characterize the cart, cck, and pyy genes, and to quantify their expression in the brain and intestine of the fish by quantitative polymerase chain reaction (qPCR). The animals were exposed to three salinities: 0, 6, and 12 parts per thousand (ppt) of salt for 21 days. Furthermore, lipid peroxidation, reactive oxygen species, DNA damage, and membrane fluidity in blood cells were quantified by flow cytometry. The results indicated an increased expression of cart, pyy, and cck and a decreased expression of npy in the brain, and the same with cck and npy in the intestine of fish treated with 12 ppt. This modulation and other adaptive responses may have contributed to the decrease in weight gain, specific growth rate, and final weight. In addition, we showed oxidative damage in blood cells resulting from increasing salinity. These results provide essential data on O. niloticus when exposed to high salinities that have never been described before and generate knowledge necessary for developing biotechnologies that may help improve the production of economically important farmed fish.

The complete mitochondrial genome of an endemic cichlid Etroplus canarensis from Western Ghats, India (Perciformes: Cichlidae) and molecular phylogenetic analysis

BACKGROUND

The Indian endemic cichlid Etroplus canarensis (Canara pearl spot) is an endangered fish and is one among the three Indian cichlids (Etroplinae) that had a restricted distribution in the South Canara region of Karnataka, India. Despite considerable investigations, the phylogeny of Indian Cichlids and its biogeographical origin is still ambiguous and remains a question under discussion which is scrutinized based on whole mitogenomes in the present study.

METHODS AND RESULTS

We report the 16,339 bp complete mitochondrial genome of E. canarensis for the first time using the next-generation sequencing methods. Comparison of gene arrangement and genome characterization was found to commensurate with the previous reports on two Indian cichlid fishes, E. suratensis and E. maculatus. ND6 has been identified as a gene with the highest evolutionary rate and COI and COII is the most conserved gene based on p-genetic distance calculation. Substitution rate (ka/ks) was found to be very low indicating a reduced rate of evolution among subfamily Etroplinae accounting for its subsided species divergence of Indian cichlids. Phylogenetic analysis of Indian cichlids based on a combined dataset of 12 protein-coding genes representing cichlids generated high posterior probability values pillaring paraphyletic nature of Indian Malagasy lineage and monophyletic Indian genus Etroplus.

CONCLUSION

The mitogenome sequence of E. canarensis may provide fundamental molecular data useful for further researches on genetic diversity, endemicity and the conservation of this endangered freshwater fish.

Infection of Tilapia tilapinevirus in Mozambique Tilapia (Oreochromis mossambicus), a Globally Vulnerable Fish Species

Tilapia tilapinevirus, or tilapia lake virus (TiLV), is a highly contagious virus found in tilapia and its hybrid species that has been reported worldwide, including in Asia, the Americas, and Africa. In this study, we experimentally challenged Mozambique tilapia (Oreochromis mossambicus) with a virulent TiLV strain, VETKU-TV01, at both low (1 × 10³ TCID₅₀/mL) and high (1 × 10⁵ TCID₅₀/mL) concentration. After the challenge, the Mozambique tilapia showed pale skin with some hemorrhage and erosion, lethargy, abdominal swelling, congestion around the eye, and exophthalmos; there was a cumulative mortality rate at 48.89% and 77.78% in the groups that received the low and high concentration, respectively. Quantitative PCR and in situ hybridization confirmed the presence of TiLV in the internal organs of moribund fish. Notably, severe histopathological changes, including glycogen depletion, syncytial hepatic cells containing multiple nuclei and intracytoplasmic inclusion bodies, and infiltration of melanomacrophage into the spleen, were frequently found in the Mozambique tilapia challenged with high TiLV concentration. Comparatively, the infectivity and pathology of the TiLV infection in Mozambique tilapia and red hybrid tilapia (Oreochromis spp.) were found to be similar. Our results confirmed the susceptibility of Mozambique tilapia, which has recently been determined to be a vulnerable species, to TiLV infection, expanding knowledge that the virus can cause disease in this fish species.

Supraspecific units in correlative niche modeling improves the prediction of geographic potential of biological invasions

BACKGROUND

Biological invasions rank among the most significant threats to biodiversity and ecosystems. Correlative ecological niche modeling is among the most frequently used tools with which to estimate potential distributions of invasive species. However, when areas accessible to the species across its native distribution do not represent the full spectrum of environmental conditions that the species can tolerate, correlative studies often underestimate fundamental niches.

METHODS

Here, we explore the utility of supraspecific modeling units to improve the predictive ability of models focused on biological invasions. Taking into account phylogenetic relationships in correlative ecological niche models, we studied the invasion patterns of three species (Aedes aegypti, Pterois volitans and Oreochromis mossambicus).

RESULTS

Use of supraspecific modeling units improved the predictive ability of correlative niche models in anticipating potential distributions of three invasive species. We demonstrated that integrating data on closely related species allowed a more complete characterization of fundamental niches. This approach could be used to model species with invasive potential but that have not yet invaded new regions.

Two complete mitochondrial genomes of Myloplus rubripinnis and Metynnis hypsauchen (Characiforme: Serrasalmidae)

Myloplus rubripinnis and Metynnis hypsauchen are two compressed-bodied ornamental fishes of Serrasalmidae family. In this study, complete mitochondrial genome sequences of the two species were determined. The mitogenomes were 16662 bp and 16737 bp nucleotides in length, and both contained 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNA), 2 ribosomal RNAs (rRNA) and a control region. The phylogenetic tree revealed that Myloplus rubripinnis was closely related to Myleus sp. and Myleus cf. schomburgkii, while Metynnis hypsauchen was related to Pygocentrus nattereri, and then the two clades clustered into one group. Present mitogenome sequences of M. rubripinnis and M. hypsauchen will provide molecular information to the evolution and ecology studies of the two species.

East African cichlid lineages (Teleostei: Cichlidae) might be older than their ancient host lakes: new divergence estimates for the east African cichlid radiation

BACKGROUND

Cichlids are a prime model system in evolutionary research and several of the most prominent examples of adaptive radiations are found in the East African Lakes Tanganyika, Malawi and Victoria, all part of the East African cichlid radiation (EAR). In the past, great effort has been invested in reconstructing the evolutionary and biogeographic history of cichlids (Teleostei: Cichlidae). In this study, we present new divergence age estimates for the major cichlid lineages with the main focus on the EAR based on a dataset encompassing representative taxa of almost all recognized cichlid tribes and ten mitochondrial protein genes. We have thoroughly re-evaluated both fossil and geological calibration points, and we included the recently described fossil †Tugenchromis pickfordi in the cichlid divergence age estimates.

RESULTS

Our results estimate the origin of the EAR to Late Eocene/Early Oligocene (28.71 Ma; 95% HPD: 24.43-33.15 Ma). More importantly divergence ages of the most recent common ancestor (MRCA) of several Tanganyika cichlid tribes were estimated to be substantially older than the oldest estimated maximum age of the Lake Tanganyika: Trematocarini (16.13 Ma, 95% HPD: 11.89-20.46 Ma), Bathybatini (20.62 Ma, 95% HPD: 16.88-25.34 Ma), Lamprologini (15.27 Ma; 95% HPD: 12.23-18.49 Ma). The divergence age of the crown haplochromine H-lineage is estimated to 22.8 Ma (95% HPD: 14.40-26.32 Ma) and of the Lake Malawi radiation to 4.07 Ma (95% HDP: 2.93-5.26 Ma). In addition, we recovered a novel lineage within the Lamprologini tribe encompassing only Lamprologus of the lower and central Congo drainage with its divergence estimated to the Late Miocene or early Pliocene. Furthermore we recovered two novel mitochondrial haplotype lineages within the Haplochromini tribe: 'Orthochromis' indermauri and 'Haplochormis' vanheusdeni.

CONCLUSIONS

Divergence time estimates of the MRCA of several Tanganyika cichlid tribes predate the age of the extant Lake Tanganyika basin, and hence are in line with the recently formulated "Melting-Pot Tanganyika" hypothesis. The radiation of the 'Lower Congo Lamprologus clade' might be linked with the Pliocene origin of the modern lower Congo rapids as has been shown for other Lower Congo cichlid assemblages. Finally, the age of origin of the Lake Malawi cichlid flock agrees well with the oldest age estimate for lacustrine conditions in Lake Malawi.

Nonadditive and allele-specific expression of insulin-like growth factor 1 in Nile tilapia (Oreochromis niloticus, ♀) × blue tilapia (O. aureus, ♂) hybrids

Hybrid Nile tilapia (Oreochromis niloticus, ♀) × blue tilapia (O. aureus, ♂) is a widely cultured tilapia variety due to its growth vigor compared to the parent species. As a peptide hormone, insulin-like growth factor 1 (IGF-1) plays a critical role in regulating somatic growth. The present study focuses on the expression characteristics of IGF-1 in hybrid tilapia. The cloned complete open reading frame of IGF-1 in hybrid tilapia is 549 bp in length, encoding a protein of 182 amino acids. The deduced protein is highly similar to that of Nile tilapia and blue tilapia. IGF-1 was found to be primarily expressed in the liver and muscle in the hybrid; lower expression levels were found in other tissues such as the intestine, spleen, and head-kidney. Increased mRNA expression was observed in the liver and muscle of the hybrid compared to Nile tilapia and blue tilapia, indicating a nonadditive expression pattern in the hybrid. An IGF-1 SNP site (397 site: C in Nile tilapia, G in blue tilapia) for differentiating the Nile tilapia or blue tilapia subgenome in hybrids was identified. Pyrosequencing analysis of the liver transcriptome indicated that most of the hybrids (9 of 10 individuals) predominantly expressed the G allele, demonstrating bias of the blue tilapia subgenome. The present study provides novel data indicating, for the first time, overall gene expression of IGF-1 and allele-specific expression in hybrid tilapia.

Mitochondrial genome annotation and phylogenetic placement of Oreochromis andersonii and O. macrochir among the cichlids of southern Africa

Genetic characterization of southern African cichlids has not received much attention. Here, we describe the mitogenome sequences and phylogenetic positioning of Oreochromis andersonii and O. macrochir among the African cichlids. The complete mitochondrial DNA sequences were determined for O. andersonii and O. macrochir, two important aquaculture and fisheries species endemic to southern Africa. The complete mitogenome sequence lengths were 16642 bp and 16644 bp for O. andersonii and O. macrochir respectively. The general structural organization follows that of other teleost species with 13 protein-coding genes, 2 rRNAs, 22 tRNAs and a non-coding control region. Phylogenetic placement of the two species among other African cichlids was performed using Maximum Likelihood (ML) and Bayesian Markov-Chain-Monte-Carlo (MCMC). The consensus trees confirmed the relative positions of the two cichlid species with O. andersonii being very closely related to O. mossambicus and O. macrochir showing a close relation to both species. Among the 13 mitochondrial DNA protein coding genes ND6 may have evolved more rapidly and COIII was the most conserved. There are signs that ND6 may have been subjected to positive selection in order for these cichlid lineages to diversify and adapt to new environments. More work is needed to characterize the southern Africa cichlids as they are important species for capture fisheries, aquaculture development and understanding biogeographic history of African cichlids. Bio-conservation of some endangered cichlids is also essential due to the threat by invasive species.

Transcriptome analysis reveals novel insights into the response of low-dose benzo(a)pyrene exposure in male tilapia

Despite a wide number of toxicological studies that describe benzo[a]pyrene (BaP) effects, the metabolic mechanisms that underlie these effects in fish are largely unknown. Of great concern is the presence of BaP in aquatic systems, especially those in close proximity to human activity leading to consumption of potentially contaminated foods. BaP is a known carcinogen and it has been reported to have adverse effects on the survival, development and reproduction of fish. The purpose of this study was to investigate if a low dose of BaP can alter genes and key metabolic pathways in the liver and testis in male adult tilapia, and whether these could be associated with biological endpoints disruption. We used both high-throughput RNA-Sequencing to assess whole genome gene expression following repeated intraperitoneal injections of 3 mg/kg of BaP (every 6 days for 26 days) and morphometric endpoints as indicators of general health. Condition factor (K) along with hepatosomatic and gonadosomatic indices (morphometric parameters) were significantly lower in BaP-treated fish than in controls. BaP exposure induced important changes in the gene expression pattern in liver and testis as revealed by both Pathway and Gene Ontology (GO) analyses. Alterations that were shared by both tissues included arachidonic acid metabolism, androgen receptor to prostate-specific antigen signaling, and insulin-associated effects on lipogenesis. The most salient liver-specific effects included: biological processes involved in detoxification, IL6-associated insulin resistance, mTOR hyperactivation, mitotic cytokinesis, spindle pole and microtubule binding. BaP effects that were confined to the testis included: immune system functions, inflammatory response, estrogen and androgen metabolic pathways. Taken together, gene expression and morphometric end point data indicate that the reproductive success of adult male tilapia could be compromised as a result of BaP exposure. These results constitute new insights on the mechanism of action of low dose BaP in a non-model organism (tilapia).

Differentiating collagens based on mitochondrion 12SrRNA gene

Aquatic collagens are one of the main collagens sold in the market due to superior physicochemical and biological activities. In this work, the species of three types of aquatic and commercial collagens were identified by molecular biotechnology. After isolating DNA from bovine, porcine and three types of aquatic animals, DNA was dissolved in a storage buffer. The animals' mitochondrion 12SrRNA sequences were downloaded from the GenBank database, and three pairs of primers that can be used to detect the aquatic collagens were designed by Primer Premier 6 and evaluated by Oligo 7. Analysis of the polymerase chain reaction and agarose electrophoresis showed that the fragments were 440, 307, 112 and 270bp, respectively, thereby enabling successful detection of the collagen species. Results indicate that PCR-based detection methods can also suitably trace the species of aquatic collagens.

The complete mitochondrial genome of the Chinese Daphnia pulex (Cladocera, Daphniidae)

Daphnia pulex has played an important role in fresh-water ecosystems. In this study, the complete mitochondrial genome of Daphnia pulex from Chaohu, China was sequenced for the first time. It was accomplished using long-PCR methods and a primer-walking sequencing strategy with genus-specific primers. The mitogenome was found to be 15,306 bp in length. It contained 13 protein-coding genes, two rRNA genes, 22 tRNA genes and a typical control region. This research revealed an overall A+T content of 64.50%. All of the 22 typical animal tRNA genes had a classical clover-leaf structure except for trnS1, in which its DHU arm simply formed a loop. The lengths of small and large rRNA were 744 bp and 1,313 bp, respectively. The A+T-rich region was 723 bp in length, which is longer than that from the North American species (689 bp). In terms of structure and composition, many similarities were found between the Chinese and North American Daphnia pulex.

The first complete mitochondrial genome of the Maylandia zebra

Maylandia zebra, a member of the family cichlid living in individual African lakes, are regarded as a significant evolution model. Recently the genome sequencing had been done, but there is no sufficient information about its mitochondria. Herein, we first assembled the complete mitochondrial genome sequence of Maylandia zebra. It is a 16 582 bp long sequence with most mitogenome's characteristic structure, 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and 1 putative control region. The GC-content of our fresh sequence is 45.86%, similar to closely related species Oreochromis niloticus. The accuracy and utility of new determined mitogenome sequences can be verified by the phylogenetic analysis, based on whole mitogenome alignment with Neolamprologus brichardi, Pseudotropheus crabro, Oreochromis niloticu, which is closest relative to Maylandia zebra, and 6 others. Using the full mitogenome, we expect to address taxonomic issues and study the related evolution events. Moreover, this is the first report of the mitogenome of genus Maylandia.

The complete mitochondrial genome sequence of Hemibagrus sp. (Siluriformes: Bagridae)

At present, the phylogenetic and taxonomic positions of Bagridae and Siluriformes have long been unclear. In this paper, we sequenced and annotated the complete mitogenome of Hemibagrus sp. The total length was 16,529 bp, and was typically consist of 37 genes, including 13 protein-coding genes, 2 rRNAs, 22 tRNA, a light-strand replication origin (OL) and a single large control region (CR). Except for eight tRNA and ND6 genes, all other mitochondrial genes were encoded on the heavy strand (H-strand). The gene content, organization and arrangement were identical to that of a typical bony fish. The overall base composition was 26.5%, 26.8%, 31.7% and 15.0% for T, C, A and G, respectively, with a slight bias on AT content (58.2%). This information could not only contribute to provide useful molecular data for the species identification, but also to further taxonomic and phylogenetic studies of Hemibagrus and Bagridae.

The complete mitochondrial genome of Western rainbowfish (Melanotaenia australis Castelnau, 1875)

In this study, the mitochondrial genome of Melanotaenia australis Castelnau, 1875 (Atheriniformes:Melanotaeniidae) was sequenced for the first time. The assembled mitogenome consisting of 16,530 bp, includes 13 protein-coding genes, 22 transfer RNAs, two ribosomal RNAs genes and one putative control region. The overall base composition of M. australis is 27.79% for A, 29.66% for C, 15.90% for G, 26.66% for T and shows 92% identities to Lake Kutubu Rainbowfish, Melanotaenia lacustris. These data would provide useful molecular information for phylogenetic relationships within the family Melanotaeniidae species.

The complete mitochondrial genome of Neon rainbowfish (Melanotaenia praecox Weber & de Beaufort, 1922)

In this study, the mitochondrial genome of Melanotaenia praecox Weber and de Beaufort, 1922(Atheriniformes: Melanotaeniidae) was sequenced for the first time. The assembled mitogenome consisting of 16,536 bp, includes 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs genes and 1 putative control region. The overall base composition of M. praecox is 27.51% for A, 29.97% for C, 16.18% for G, 26.34% for T and shows 89% identities to Lake Kutubu Rainbowfish, Melanotaenia lacustris. These data would provide useful molecular information for phylogenetic relationships within the family Melanotaeniidae species.

The complete mitochondrial genome sequence of Yongeichthys criniger and phylogenetic studies of Gobiidae

Yongeichthys criniger belongs to Gobiidae, Gobioidei, and Perciformes in taxonomy. Its mitochondrial genome was first determined, which consists of 13 typical vertebrate protein-coding genes, 22 tRNA, 2 rRNA genes, and 1 control region. The mitogenome base's composition is 27.28% for A, 26.12% for T, 28.98% for C, and 17.62% for G. The phylogenic analysis involves 32 Gobiidae species in GenBank database. The results will provide more molecular information for the further studies on species identification and phylogenic evolution of Gobiidae.

The complete mitochondrial genome of Triplophysa sp. (Teleostei: Cypriniformes: Balitoridae)

The complete mitochondrial genome sequence of balitorid fish, Triplophysa sp., which was from Qinling mountains, central China, has been sequenced by the long polymerase chain with primer walking method. The mitochondrial genome of Triplophysa sp. is similar to those of the typical vertebrates, 16 570 bp in length, including 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and one control region (D-loop). Most mitochondrial genes are encoded on the heavy strand, except for ND6 and eight tRNA genes which are encoded on the light strand. The overall base composition of the heavy strand of the Triplophysa sp. mitogenome is A: 28.0%, T: 28.0%, C: 25.8%, and G: 18.2%. Combined with the complete mitogenome sequences of other 15 balitorids, the topology demonstrated that Triplophysa sp. has a close relationship with the cluster consisting of Triplophysa yarkandensis, Triplophysa siluroides, and Triplophysa robusta with high support values. The genera Triplophysa and Barbatula formed a sister-group relationship. Further investigations with more Triplophysa species included need to be performed to better understand the evolutionary history of this intriguing genus.

The complete mitochondrial genome of Boeseman's rainbowfish (Melanotaenia boesemani Allen & Cross, 1980)

In this study, the mitochondrial genome of Melanotaenia boesemani (Allen & Cross, 1980 ) (Atheriniformes: Melanotaeniidae) was sequenced for the first time. The assembled mitogenome consisting of 16 493 bp, includes 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs genes and 1 putative control region. The overall base composition of M. boesemani is 27.88% for A, 29.92% for C, 15.74% for G, 26.47% for T and shows 96% identities to Lake Kutubu rainbowfish, Melanotaenia lacustris. These data would provide useful molecular information for phylogenetic relationships within the family Melanotaeniidae species.

The mitochondrial genome of an endangered native Singidia tilapia, Oreochromis esculentus: genome organization and control region polymorphism

Singidia tilapia (Oreochromis esculentus) is a native Cichlid fish of important commercial value, distributed in Lake Victoria, East Africa. Due to its declining population levels in its natural habitat, this species has now been classified as a Critically Endangerd by the International Union for the Conservation of nature (IUCN). In the present study the complete nucleotide sequence of the mitochondrial genome (mtDNA) of O. esculentus was determined. In addition, polymorphism analysis based on the mtDNA's control region sequence was investigated on two of its remaining populations of Yala and Borabu as well as a phylogenetic consideration using 16S rRNA mtDNA genes to explore its position and relationship within Cichlidae fish. The length of the complete mitogenome of O. esculentus is 16 622 bp, containing the same order and an identical number of genes and regions with the other reported Cichlid fishes, which consists of 13 protein-coding genes, 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and a putative non-coding region. The phylogenetic analysis shows O. esculentus being clustered within the Oreochromini sub-tribe of the Cichlidae. The high genetic diversity and low genetic differentiation between the two populations indicated the need for conservation of both the refuge ecosystems and the fish species under study.

The complete mtDNA genome of Triplophysa dorsalis (Cypriniformes, Balitoridae, Cobitoidea): genome characterization and phylogenetic analysis

Based upon the morphological characters, the genus Triplophysa (plateau Loach) is a highly diverse group in the family Balitoridae (or Cypriniformes, Cobitoidea) with 133 valid species. Therefore, the taxonomic relationship of this species at the genetic level remains ambiguous. In the present study, we sequenced the complete mitochondrial genome of Triplophysa dorsalis. In order to understand its position and genetic background at the gene level, the characteristics of mitochondrial DNA sequences and phylogenetic relationship were examined. The mitochondrial genome of T. dorsalis is similar to those of the typical vertebrates, 16 572 bp in length, including 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, and a non-coding control region (D-loop). All genes were encoded on the heavy strand except for ND6 and 8 tRNA genes. The overall base composition of the heavy strand was 28.16%, 28.41%, 25.62% and 17.82% for A, T, C and G, respectively. Phylogenetic analyses showed that the seven Triplophysa species clustered together with T. dorsalis to form a sister group with Triplophysa strauchii, T. bleekeri, T. stoliczkai and T. bombifrons. The two genera Triplophysa and Barbatula formed a sister-group relationship, the species Homatula potanini located in the intermediate position, and the genus Leptobotia elongata was in the basal position in the subfamily Nemacheilidae. Further investigations with more Triplophysa species need to be performed for better understanding of the evolutionary history of this fascinating genus.

DNA barcoding of feral tilapias in Philippine lakes

Tilapia (Oreochromis mossambicus) was first introduced to the Philippines in 1950 for aquaculture. Since then, other species of tilapia have been introduced to the country and some of them (mainly Oreochromis niloticus) have become established in lakes and other water bodies. In this study, DNA barcoding using the mitochondrial cytochrome c oxidase subunit I (COI) gene was done to assess the reliability of morphological identification and the degree of introgression among feral tilapias (Oreochromis spp.) in seven major Philippine lakes, namely Laguna de Bay, Lake Lanao, Taal Lake, Lake Mainit, Lake Naujan, Lake Bato, and Lake Buhi. Specimens were also collected from a private hatchery in Sual, Pangasinan to serve as reference. Morphological traits, Nucleotide BLAST (BLASTn), and Translated BLAST (BLASTx) analyses were used to classify the specimens. A Neighbor-Joining tree was constructed using the Kimura 2-Parameter method, incorporating 66 COI sequences generated from the study and 20 additional reference sequences obtained from GenBank. Three Oreochromis clusters were obtained and were classified as the O. niloticus group, O. mossambicus group, and O. aureus group, with bootstrap support values of 99%, 74%, and 99%, respectively. The mean K2P genetic distances within each group were 0.008%, 0.959%, and 0.086%, respectively. The clustering of COI sequences generated from this study corresponded with the results of the BLASTn analysis. Oreochromis hybrids were also found in all the lakes. The study highlights the usefulness of DNA barcoding for molecular identification and detection of introgressed individuals, with potential applications in management of feral stocks.

The first complete mitochondrial genome of the Pundamilia nyererei

Pundamilia nyererei, a member of the family cichlid lived in individual African lakes, regarded as a significant evolution model. Recently the genome sequencing had been done, but no more information of its mitochondrial reported. Herein, we first assembled the complete mitochondrial genome sequence of Pundamilia nyererei. It is a 16 758 bp long sequence with most mitogenome's characteristic structure, 13 protein-coding genes, 20 of tRNA genes, two of rRNA genes, and one putative control region. The GC-content of our fresh sequence is 45.24%, similar to closely related species Oreochromis niloticus. It can verify the accuracy and the utility of new determined mitogenome sequences by the phylogenetic analysis, based on whole mitogenome alignment with Dimidiochromis compressiceps, which is closest relative to Pundamilia nyererei, and seven others. We expect that using the full mitogenome to address taxonomic issues and study the related evolution events. Moreover, this is the first report of the mitogenome of genus Pundamilia nyererei.

The complete mitochondrial genome of red rainbowfish (Glossolepis incises Weber 1907)

In this study, the mitochondrial genome of Glossolepis incisus (Weber 1907 ) (Atheriniformes: Melanotaeniidae) was sequenced for the first time. The assembled mitogenome consisting of 16 529 bp, includes 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs genes and 1 putative control region. The overall base composition of G. incisus is 27.51% for A, 30.04% for C, 16.06% for G, 26.39% for T and showS 91% identities to Lake Kutubu Rainbowfish, Melanotaenia lacustris. These data will provide useful molecular information for phylogenetic relationships within the family Melanotaeniidae species.

The complete mitochondrial genome sequence of Symphysodon discus Heckel (1840)

The complete mitochondrial genome of Symphysodon discus Heckel was 16 544 bp in length, consisting of 22 tRNA genes, 13 protein-coding genes, 2 ribosomal rRNA genes, and a control region or displacement loop (D-loop). With the exception of 8 tRNAs and ND6 genes, the others were encoded on H-strand. The base composition on H-strand was 30.04% C, 28.39% A, 26.49% T and 15.07% G, exhibiting an A + T rich pattern. The codon usage was consistent with the other vertebrate mitochondrial pattern, i.e. start codon is ATG or GTG and stop codons are TAA, TAG or T- -. Stop codon TAG was only found in the ND6. There were 8 regions of gene overlapped with the length of 26 bp in total and 12 intergenic spacer regions (99 bp in total).

Complete mitochondrial DNA sequences of the Victoria tilapia (Oreochromis variabilis) and Redbelly Tilapia (Tilapia zilli): genome characterization and phylogeny analysis

The Cichlid fishes have played an important role in evolutionary biology, population studies and aquaculture industry with East African species representing a model suited for studying adaptive radiation and speciation for cichlid genome projects in which closely related genomes are fast emerging presenting questions on phenotype-genotype relations. The complete mitochondrial genomes presented here are for two closely related but eco-morphologically distinct Lake Victoria basin cichlids, Oreochromis variabilis, an endangered native species and Tilapia zilli, an invasive species, both of which are important economic fishes in local areas. The complete mitochondrial genomes determined for O. variabilis and T. zilli are 16 626 and 16,619 bp, respectively. Both the mitogenomes contain 13 protein-coding genes, 22 tRNAs, 2 rRNAs and a non-coding control region, which are typical of vertebrate mitogenomes. Phylogenetic analyses of the two species revealed that though both lie within family Cichlidae, they are remotely related.

Assembly and variation analyses of Clarias batrachus mitogenome retrieved from WGS data and its phylogenetic relationship with other catfishes

Whole genome sequencing (WGS) using next generation sequencing technologies paves the way to sequence the mitochondrial genomes with greater ease and lesser time. Here, we used the WGS data of Clarias batrachus, generated from Roche 454 and Ion Torrent sequencing platforms, to assemble the complete mitogenome using both de novo and reference based approaches. Both the methods yielded almost similar results and the best assembled mitogenome was of 16,510 bp size (GenBank Acc. No. KM259918). The mitogenome annotation resulted in 13 coding genes, 22 tRNA genes, 2 rRNA genes and one control region, and the gene order was found to be identical with other catfishes. Variation analyses between assembled and the reference (GenBank Acc. No. NC_023923) mitogenome revealed 51 variations. The phylogenetic analysis of coding DNA sequences and tRNA supports the monophyly of catfishes. Two SSRs were identified in C. batrachus mitogenome, out of which one was unique to this species. Based on the relative rate of gene evolution, protein coding mitochondrial genes were found to evolve at a much faster pace than the d-loop, which in turn are followed by the rRNAs; the tRNAs showed wide variability in the rate of sequence evolution, and on average evolve the slowest. Among the coding genes, ND2 evolves most rapidly. The variations present in the coding regions of the mitogenome and their comparative analyses with other catfish species may be useful in species conservation and management programs.

Complete mitochondrial genome of Kashgarian loach, Triplophysayarkandensis (Day, 1877) in the Tarim river

Kashgarian loach, Triplophysayarkandensis (Day, 1877), a native species in the Tarim River of Northwest China, has been dramatically declined in population size in recent years. In this article, the mitochondrial genome of Kashgarian loach was first determined. The whole mtDNA sequence was 16,574 bp in length, which is similar to other bony fishes in gene order, including 2rRNA genes, 22tRNA, 13 protein-coding and 1 putative control region.

Characterization of mitochondrial ATPase 6/8 genes in wild Labeo calbasu (Hamilton, 1822) and mapping of natural genetic diversity

We characterized mitochondrial ATP synthase (ATPase) 6 and 8 genes in Labeo calbasu (Hamilton, 1822) and determined genetic variation in wild populations across the natural distribution in Indian rivers. A total of 206 individuals were sampled from 11 riverine sites belonging to distinct geographical locations covering five major river basins. Sequencing of 842 base pairs of ATPase 6/8 revealed 21 haplotypes with haplotype diversity ranging from 0.1250 (River Satluj) to 0.8846 (River Bhagirathi). Analysis of molecular variance (AMOVA) of mitochondrial DNA (mtDNA) data revealed significant genetic differentiation among sites (FST = 0.192, p < 0.0001) which was indicative of moderate level of genetic structuring in the wild L. calbasu populations. The patterns of genetic divergence and haplotype network of mtDNA revealed distinct clades present in Indian rivers. The analysis of data demonstrated the potential of ATPase 6/8 genes in determining the genetic diversity and indicated considerable sub-structuring in wild calbasu populations present in different rivers.

Complete F-type mitochondrial genome of freshwater mussels Unio douglasiae

The complete F-type mitochondrial genome of Unio douglasiae is reported for the first time in this research. It is 15,767 bp in size and contains 13 protein-coding genes, 22 tRNA genes, and 2 rRNA genes. Except for COI, ND2, CYTB, ND1, ND6, ND4L, ATP8 with ATA start codon, and ND4 with ATT start codon, the remaining protein-coding genes initiate with the orthodox ATG start codon. There are 25 noncoding regions found throughout the mitogenome of Unio douglasiae, ranging in the size from 1 to 312 bp, the largest of which is between tRNA^Glu and ND2 (312 bp).

The complete mitochondrial genome of the midas cichlid (Amphilophus citrinellus)

The midas cichlid (Amphilophus citrinellus) is an important aquarium fish that has served as a model organism for studying sympatric speciation. In this study, we sequenced the complete mitochondrial genome of the midas cichlid. We report that the cichlid's mitochondrial genome is a circular DNA double strand of 16,521 bp length, which contains 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and 1 control region. The overall-base compositions of the H-strand are as follows: A, 28.56%; C, 30.69%; G, 15.11%; T, 25.64%. This study provides important genomic data to further the research of the genetic evolution of cichlids.

Complete mitochondrial DNA sequence of the Eastern keelback mullet Liza affinis

Eastern keelback mullet (Liza affinis) inhabits inlet waters and estuaries of rivers. In this paper, we initially determined the complete mitochondrial genome of Liza affinis. The entire mtDNA sequence is 16,831 bp in length, including 2 rRNA genes, 22 tRNA genes, 13 protein-coding genes and 1 putative control region. Its order and numbers of genes are similar to most bony fishes.

Mitochondrial genome of the sucking disc gudgeon, Discogobio yunnanensis (Teleostei, Cypriniformes)

The complete mitochondrial genome of Discogobio yunnanensis was determined using the polymerase chain reaction and directly sequenced with the primer walking method. The whole mitogenome was 16,602 bp in length, consisting of 13 protein-coding genes, 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes and 1 control region. It had the typical circular molecule structure of vertebrate's mitogenome. The whole base composition was estimated to be 32.10% A, 26.79% T, 25.95% C, 15.16% G with AT bias of 58.89%. The complete mitogenome of D. yunnanensis provides the fundamental data for conservation genetics study on this freshwater fish species.

The complete mitochondrial genome sequence of Jinshaia abbreviata (Cypriniformes, Balitoridae)

Jinshaia abbreviata, belonging to the family Balitoridae in Cypriniformes, is endemic to the Upper Yangtze River with most population distributed in the Jinsha River. In this study, the complete mitochondrial genome of J. abbreviata was sequenced with its structure analyzed. The mitochondrial genome of J. abbreviata is similar to those of the typical vertebrates, 16,567 bp in length, including 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and one non-coding control region (D-loop). The D-loop of J. abbreviata was characterized by one termination-associated sequence with two pair of motifs and six conserved sequence blocks (CSB-F, CSB-E, CSB-D, and CSB I-III). The mitogenome sequence of J. abbreviata could contribute to estimate the phylogenetic relationship of the Balitoridae. And further investigations with more Jinshaia species and individuals included need to be performed to better understand the speciation process and evolutionary history of the genus Jinshaia.

Complete mitochondrial DNA sequencing of Vieja synspila, a cichlid fish

The Redhead cichlid (Vieja synspila) is an important aquarium fish and a useful phylogenetic organism of the Cichlidae family. In this study, we sequenced the mitochondrial genome of the Redhead cichlid for the first time. The mitogenome (16,543 bp) had the typical mitochondrial characteristics of other cichlid fish, including 13 protein-coding, 22 tRNA, two rRNA genes and one putative control region. This sequence will be helpful in studying the phylogenetic relationships between cichlid fish.

Complete mitochondrial DNA sequence of marble goby, Oxyeleotris marmorata (Bleeker, 1852)

Marble goby, Oxyeleotris marmorata (Bleeker) is a large-scale invasive goby in China. In this study, the mitochondrial genome of marble goby was firstly determined. The entire mtDNA sequence was 16,556 bp in length with 13 protein-coding genes, 22 transfer RNA genes (tRNAs), 2 ribosomal RNA genes (rRNAs) and control region (CR). Its mitochondrial genome has the common features with those of other bony fishes with respect to gene arrangement, base composition, and tRNA structures.

Comparative analysis of mitochondrial genomes in distinct nuclear ploidy loach Misgurnus anguillicaudatus and its implications for polyploidy evolution

Misgurnus anguillicaudatus has several natural ploidy types. To investigate whether nuclear polyploidy have an impact on mitochondrial DNA (mtDNA), the complete mitochondrial genomes (mitogenomes) of five distinct ploidy M. anguillicaudatus (natural diploid, triploid, tetraploid, pentaploid and hexaploid), which were collected in central China, were sequenced and analyzed. The five mitogenomes share the same gene arrangement and have similar gene size, base composition and codon usage pattern. The most variable regions of the mitogenome were the protein-coding genes, especially the ND4L (5.39% mutation rate). Most variations occurred in tetraploids. The phylogenetic tree showed that the tetraploid M. anguillicaudatus separated early from other ploidy loaches. Meanwhile, the mitogenomes from pentaploids, and hexaploids have the closest phylogenetic relations, but far from that of tetraploids, implying that pentaploids and hexaploids could not be formed from tetraploids, possibly from the diploids and triploids. The genus Misgurnus species were divided into two divergent inter-genus clades, and the five ploidy M. anguillicaudatus were monophyletic, which support the hypotheses about the mitochondrial introgression in loach species.

Two homologs of rho-class and polymorphism in alpha-class glutathione S-transferase genes in the liver of three tilapias

To clarify detoxification metabolism of tilapia, a natural and biological control for removing the leftover toxicants in fresh water, sequence structure, expression profile and polymorphisms of members of glutathione S-transferase (GST) genes were analyzed in Nile tilapia, blue tilapia and their hybrid. Full-length mRNA sequences of alpha-class GST (GSTA) and two homologs of rho-class GST (GSTR) were identified. Sequence analysis confirmed the similarity in conserved domain regions and their phylogenetic relationships with GST genes in other fishes. In addition, three single nucleotide polymorphisms of GSTA genes were identified in the three populations, two (C266T and G525A) of which showed significant association. The relative mRNA expression of GSTA gene was significantly (P<0.05) increased in the liver of Nile tilapia at 24h post-injection of MC-LR, significantly (P<0.05) decreased in blue tilapia whereas slightly decreased (P>0.05) in hybrid tilapia.

The complete mitochondrial genome of Aspiorhynchus laticeps and its phylogenetic analysis

The complete nucleotide sequence of the mitochondrial genome (mitogenome) of Aspiorhynchus laticeps was determined. The length of the complete mitochondrial DNA sequence of A. laticeps is 16,591 bp, which consists of 13 protein-coding genes, 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and a non-coding region 'D-loop'. Except for the D-loop, another non-coding region named replication origin of L-strand (OL) region was also found. According to the phylogenetic analysis, A. laticeps has a closer relationship with Schizothorax.