Naked Carp Gymnocypris Przewalskii Research Articles

Comparisons of fecundity and reproductive hormone levels in three populations of Gymnocypris przewalskii

The naked carp Gymnocypris przewalskii (Kessler, 1876) is the only economical fish in the Lake Qinghai. In order to determine the relationship between spawning behavior, gonadal development and reproductive hormone levels of the naked carp, we surveyed three populations: artificial farming population (AP), freshwater wild population (FP) and saltwater wild population (SP). This study was conducted from August 2016 to June 2017. A total of 339 naked carps were collected by gill net and purse seine. The body length, body weight, age composition, gonadal development were determined by using conventional biological methods. The fecundity statistics were carried out for female individuals whose maturation of gonads exceeded stage IV and four reproductive hormones were detected by ELISA. The results showed that the average body length, body weight and age composition of AP, FP and SP were 293.37 ± 0.43 mm, 345.79 ± 1.52 g, 4+-10+; 306.48 ± 1.10 mm, 363.20 ± 5.21 g, 4+-20+ and 233.25 ± 0.12 mm, 150.36 ± 0.27 g, 3+-11+, respectively. The average absolute fecundity of the SP was lower than that of the other two populations, but the average relative fecundity was higher. Only the reproductive hormones in the SP had the trend of annual variation, during reproduction-peaks, the levels of reproductive hormone peaked in June. In conclusion, only the reproductive hormone levels and the migratory reproductive activities are synchronized, the natural breeding activities of the naked carp can be carried out.

Identification and characterization of microRNAs involved in scale biomineralization in the naked carp Gymnocypris przewalskii

The mineralized scale derived from skin plays a protective role for the fish body and also possesses important application values in the biomaterial field. However, little is known about fish scale biomineralization and related molecular regulatory mechanisms. Here, we used a comparative microRNA sequencing approach to identify and characterize differentially expressed microRNAs (DEMs) involved in scale biomineralization in the naked carp Gymnocypris przewalskii. A total of 18, 43, and 66 DEMs were obtained from skin tissues covered with initial, developing, and mature scales (IS, DS, and MS) compared with scale-uncovered skin. The target genes of these DEMs were significantly enriched in a sole biomineralization-related sphingolipid signaling pathway. Seven DEMs (dre-miR-124-3p, dre-miR-133a-2-5p, dre-miR-184, dre-miR-206-3p, novel_33, novel_56 and novel_75) were common in IS, DS, and MS. Dre-miR-124-3p, dre-miR-206-3p, and novel_33 were predicted to be able to target biomineralization-related genes. Stem-loop real-time quantitative PCR further confirmed that the common DEMs had higher expression levels in scale-covered skin tissues than that in the gill, intestine, and brain, except for dre-miR-133a-2-5p. Our results suggest that these identified microRNAs may play a role in scale biomineralization in G. przewalskii, and the obtained microRNAs are expected to be candidates in understanding the molecular mechanism of scale biomineralization in fish species.

The microRNA repertoire of Tibetan naked carp Gymnocypris przewalskii: A case study in Schizothoracinae fish on the Tibetan Plateau.

Tibetan naked carp Gymnocypris przewalskii is an ideal model system to study highland adaptation of fish, because it evolved specific genetic and phenotypic characteristics to adapt to chronic cold and alkaline environments in Lake Qinghai. MicroRNAs (miRNAs) are small noncoding RNAs that regulating gene expression post-transcriptionally in a wide range of biological processes. In this study, we focus on the role of miRNAs in adaptation of G. przewalskii to extreme conditions in Lake Qinghai. We generate the first miRNAome of G. przewalskii in Schizothoracinae fish. Using several genomic resources, we inferred 341 conserved miRNAs belonged to 152 miRNA families and 43 novel miRNAs in G. przewalskii, and also identified 15 teleost-specific miRNAs. Using a large scale of conserved miRNAs, we constructed a high-confidence phylogenetic tree between teleost and mammals than mitochondria and nuclear genes. In addition, we found that several miRNA family (e.g. miR-10 and let-7) members highly expressed in G. przewalskii, which may function in multiple biological processes. Finally, we predicted a total of 34,258 miRNA targets genes. Conserved miRNAs target genes participating in signal transduction, cell differentiation and biosynthetic process, and showed signature of functional constraint. While novel miRNAs in a species displayed species-specific targets and involved in ion binding, transport and oxidoreductase activity, may affect the expression patterns of targets with signature of gene family expansion or positive selection under extreme environment. Taken together, this study demonstrated that miRNAs may involve into roles of adaptation of G. przewalskii to highland aquatic environment, and also provide insights into miRNA regulatory network in Schizothoracinae fish as a case study.

Signature of adaptive evolution and functional divergence of TLR signaling pathway genes in Tibetan naked carp Gymnocypris przewalskii

The Tibetan naked carp Gymnocypris przewalskii is a newly diverged species from Schizothoracinae fish, only dwelled in the China largest salt lake, Qinghai Lake. Its living condition is hypoxia, cold temperature and high salinity. Noteworthy, it is more susceptible to parasite infection in freshwater that wild environment. Our recent genome wide analyses studies indicated that naked carp TLR signaling pathway genes, TLR4 and TLR9 within TLR family, IRF3, IRF5 and IRF7 within IRF family underwent significant positive selection in response to the inhospitable environment trigged by the uplift of the Tibetan Plateau. The experimental evidences indicate that TLR4 gene function towards neofunctionalization when exposure to parasite infection, IRF3 and IRF4 towards significant functional divergence in biotic and abiotic stress response. These finding provide novel insights into evolutionary history and molecular mechanism of highland fish respond to environment changes.

Positive Darwinian selection within interferon regulatory factor genes of Gymnocypris przewalskii (Cyprinidae) on the Tibetan Plateau.

Tibetan Plateau (TP) had experienced phased uplift, resulting in inhospitable environment of low temperature, hypoxia and high ultraviolet radiation for Tibetan wildlife. Many organisms can well adapt to TP, it is of ecological and evolutionary interest to untangle how organisms adapt to extreme environment on TP through evolution. Previous studies mainly focused on hypoxia and metabolism related genes, but we know little about the evolutionary history of immune genes in Tibetan wildlife. In this study, we first identified 10 interferon regulatory factor (IRF) genes from Tibetan naked carp Gymnocypris przewalskii. Within this gene family, IRF3, IRF5, IRF7 and IRF8 contained positive selection sites. Evidences indicated that positive selection may lead to IRF genes functional alternations, presumably driving genes towards adaptation to the environmental changes. Taken together, our results suggested 4 candidate genes as interesting targets for further experimental confirmation of their functional variations and contributions to high altitude adaptation in Tibet fish.

Oxygen and strontium isotope markers of Lake Qinghai naked carp otoliths and their implication for fish migratory pattern

As the dominant and unique species in Lake Qinghai, the naked carp Gymnocypris przewalskii (Kessler) is characterized by upstream migration to spawn during late spring and summer in each year and back lake to live during the remaining seasons, but little is known about its migratory pattern. The migratory pattern of the naked carp is significant in understanding its living habitat and in protecting this precious fish. Otoliths are paired biogenic carbonates in the inner ear of teleost fish and grow layer by layer throughout the fish life. Owing to its metabolically inert without involvement in metabolic processes after deposition, chemical compositions of daily and annual growth increments in otoliths record the water elements of the ambient waters where the fish encountered during its life history. Therefore, microchemistry variation of otoliths has been used widely to trace migration pattern of fish and to reconstruct water chemistry and environmental conditions in the past.

Stratigraphy and otolith microchemistry of the naked carp Gymnocypris przewalskii (Kessler) and their indication for water level of Lake Qinghai during the Ming Dynasty of China

Otoliths are biogenic carbonate minerals in the inner ear of teleost fish, whose compositions can record the physical and chemical conditions of the ambient water environment inhabited by individual fish. In this research, the fishbones and otoliths of naked carp sampled near the Bird Island, offshore Lake Qinghai, were dated and analyzed for mineralogy and microchemical compositions. Comparing the microchemical compositions of ancient otoliths with those of modern otoliths, we conclude that the ancient naked carps inhabited a relict lake formed when the lake shrank from a high lake level, by combining with the AMS-14C ages of fishbones and otoliths, the stratigraphy and surrounding topography of the sample site. AMS-14C dating results of ancient fishbones and otoliths show that these naked carps lived from 680 to 300 years ago, i.e. during the Ming Dynasty of China. The X-ray diffraction (XRD) patterns demonstrate that the ancient lapillus is composed of pure aragonite, identical to modern one, indicating that the mineral of lapillus didn’t change after a long time burial and that the ancient lapillus is suitable for comparative analysis thereafter. Microchemical results show that both ratios of Mg/Ca ((70.12±18.50)×10−5) and δ18O ((1.76±1.03)‰) of ancient lapilli are significantly higher than those of modern lapilli (average Mg/Ca=(3.11±0.41)× 10−5 and δ18O=(−4.82±0.96)‰). This reflects that the relict water body in which the ancient naked carp lived during the Ming Dynasty was characterized by higher Mg/Ca and δ18O ratios than modern Lake Qinghai, resulting from strong evaporation after being isolated from the main lake, similar to today’s Lake Gahai. Based upon the stratigraphy and altitude of naked carp remains, it can be inferred that the altitude of lake level of Lake Qinghai reached at least 3202 m with a lake area of 4480 km2 during the Ming Dynasty, approximately ∼5% larger than it is today.

Mineralogy of the otoliths of naked carp Gymnocypris przewalskii (Kessler) from Lake Qinghai and its Sr/Ca potential implications for migratory pattern

Otoliths are biogenic carbonate minerals whose microstructure and microchemistry have been used for age determination, stock identification, life history and environmental tracing. Using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, we have determined the mineral types and crystalline characteristics of three pairs of otoliths from naked carp Gymnocypris przewalskii, the predominant fish in Lake Qinghai. The results indicate that the mineral of both lapillus and sagitta of the naked carp is aragonite, and that of asteriscus is vaterite. The aragonite of lapillus has prefect crystallization. Given the shape of lapillus and the sensitivity of its aragonite to water chemistry, lapillus was used to analyze temporal Sr/Ca ratios along the maximal growth axis by an electron probe microanalyzer (EPMA). Consistent variations of Sr/Ca ratios with a range of 1.0×10−3–5.0×10 on the long and short radii indicate that Sr/Ca ratios of lapillus potentially respond to the chemical compositions of the host waters during the period of the naked carp’s growth and migration. Discontinuous (dark) zones of lapillus were formed during fall and winter when the naked carp grows slowly in Lake Qinghai, resulting in similar low Sr/Ca ratios to lake water, whereas incremental zones with higher Sr/Ca ratios respond to its migratory river waters during spring and summer. Various Sr/Ca ratios of incremental zones suggest that the migratory pattern of the naked carp may be much more flexible, rather than in a single river. Therefore, high-resolution otolith microchemistry of the naked carp can be used to trace its migratory behavior, which is of significance for determining its migratory pattern and life history of this precious species inhabiting the Tibetan Plateau.

Development and characterization of microsatellite markers to study population genetic diversity of Przewalski's naked carp Gymnocypris przewalskii in China

Two populations of Przewalski's naked carp Gymnocypris przewalskii, 30 individuals per population, were screened for 10 microsatellite loci. Moderate allele variation was found in these loci with two to eight alleles per locus. The expected and observed heterozygosity ranged from 0.019 to 0.805 and from 0.160 to 0.575, respectively.

Metabolic and osmotic responses of Lake Qinghai naked carp Gymnocypris przewalskii to acute hypoxia during spawning migration

Metabolic and osmotic responses of Lake Qinghai naked carp Gymnocypris przewalskii to acute hypoxia during spawning migration