虎嘉鱼保护生物学的研究V.生境特点及保护对策

本文报道了虎嘉鱼的生境特点及保护对策,主要是加强宣传教育,严禁滥捕,深入研究,开展人工养殖试验和建立自然保护区等措施,确保物种生存和繁衍。     

线粒体序列分析黑龙江流域哲罗鲑的种群遗传结构

哲罗鲑是我国土著的重要经济鱼类,近些年来,由于环境的恶化及人类活动的加剧,已对其资源量、栖息地、产卵场等造成了严重的破坏,种群处于濒危状态,被列入濒危物种红色名录中,因此研究哲罗鲑的群体遗传结构、演化历史、分布动态等对其进行有效保护具有重要意义.用线粒体Cox1和ND1基因序列对黑龙江流域内9个群体(n＝30)进行了遗传结构、群体演化分析.在30个个体中,Cox1扩增出1550bp的片段,群体间序列分歧距离在0～0.0028之间,共发现10个单倍型;ND1基因扩增出1000bp的片段,群体间序列分歧距离在0～0.0013之间,共发现7个单倍型.单倍型网络(TCS)和AMOVA分析结果均表明黑龙江流域哲罗鲑存在显著的群体分化,Cox1基因、ND1基因及组合数据的群体间Fst分别为0.0704、0.0491、0.0792,均达到显著性水平(P<0.05),根据配对群体间Fst(Pairwised Fst)可以将黑龙江流域哲罗鲑群体分为黑龙江上游群体、呼玛河群体、乌苏里江群体、内蒙古伊敏河上游群体4个地理群.9个群体共享同一个单倍型(BH11),表明这些群体具有相同的演化历史,为同一个祖先群体(黑龙江上游群体)演化而来.     

哲罗鱼消化系统器官发生发育的组织学观察

采用形态观察与连续组织切片技术,对哲罗鱼(Hucho taimen)胚胎期(水温7~8℃)和胚后期(水温3~14℃)消化系统的发生发育进行观察和研究。结果表明,哲罗鱼受精11d形成原始的消化管。受精18d肝原基出现,U型胃雏型形成。受精30d鱼体破膜,口能自由闭合。破膜8d后,齿形成,肛门与外界相通,消化道初步形成口咽腔、食道、U型胃、肠和肛门。破膜16d,胰及瓣囊出现,仔鱼消化系统初步具备了摄食和消化外源性食物的能力。破膜24d后,鱼体开始上浮,主动摄食,由内源性营养转向混合性营养。破膜30d后,卵黄囊完全被吸收,各消化器官功能和结构逐步发育完善,鱼体由混合性营养进入外源性营养阶段。此后随着鱼体的生长消化器官逐步发育成熟,舌齿和下颌齿分别为双排,胃腺发达,形成网状结构,幽门盲囊较多,肠为直行,肝和胰为相互分开的独立器官。     

Estimating the inbreeding level and genetic relatedness in an isolated population of critically endangered Sichuan taimen (Hucho Bleekeri) using genome‐wide SNP markers

Sichuan taimen (Hucho bleekeri) is critically endangered fish listed in The Red List of Threatened Species compiled by the International Union for Conservation of Nature (IUCN). Specific locus amplified fragment sequencing (SLAF‐seq)‐based genotyping was performed for Sichuan taimen with 43 yearling individuals from three locations in Taibai River (a tributary of Yangtze River) that has been sequestered from its access to the ocean for more than 30 years since late 1980s. Applying the inbreeding level and genetic relatedness estimation using 15,396 genome‐wide SNP markers, we found that the inbreeding level of this whole isolated population was at a low level (2.6 × 10^?3 ± 0.079), and the means of coancestry coefficients within and between the three sampling locations were all very low (close to 0), too. Genomic differentiation was negatively correlated with the geographical distances between the sampling locations (p < .001), and the 43 individuals could be considered as genetically independent two groups. The low levels of genomic inbreeding and relatedness indicated a relatively large number of sexually mature individuals were involved in reproduction in Taibai River. This study suggested a genomic‐relatedness‐guided breeding and conservation strategy for wild fish species without pedigree information records.     

Isolation of microsatellite DNA and analysis on genetic diversity of endangered fish,Hucho taimen (Pallas)

Hucho taimen (Pallas) is an endangered species in China. To evaluate the species’ genetic diversity and population genetic structure, we isolated six polymorphic microsatellite markers from its genomic libraries by (ACA)₁₆ enriched, and characterized using 61 wild individuals. The number of alleles per locus ranged from two to seven, expected heterozygosity ranged from 0.3200 to 0.7410, polymorphism information content ranged from 0.3047 to 0.6896. These markers will be useful for the genetic variation assessment of taimen.     

Threatened fishes of the world: <Emphasis Type="Italic">Hucho bleekeri</Emphasis> Kimura, 1934 (Salmonidae)

Conservation status, identification, distribution, habitat and ecology, reproduction, threats, conservation actions and recommendations of a critically endangered fish, Hucho bleekeri Kimura, which is endemic to China, was introduced.     

Comparative phylogeography of salmonid fishes (Salmonidae) reveals late to post-Pleistocene exchange between three now-disjunct river basins in Siberia

Abstract. We use a comparative phylogeographical framework to evaluate the hypothesis of hydrological exchange during the Pleistocene among the now disjunct Lena, Amur, and Enisei basins in Siberia, and to provide evidence on the causal mechanism of their present day faunal dissimilarities. Approximately 600 bases of the mitochondrial control region were sequenced in five distinct lineages among three genera of salmonid fishes, Hucho, Brachymystax and Thymallus. All three basins were fixed for divergent (2–5.4%) lineages of Thymallus whereas a single shared haplotype was present in all three basins for Hucho taimen ( Pallas, 1773 ) and one shared haplotype between the Lena and Amur basins out of a total of five for blunt‐snouted and one out of five for sharp‐snouted Brachymystax lenok ( Pallas, 1773 ). For both blunt‐ and sharp‐snouted lenok the haplotypes found within each basin did not form clades, so no relationship between genotypes and geographical occurrence was found. Our data support relatively recent hydrological mixing of the major river drainage systems in eastern and far‐eastern Siberia, congruent with the hypothesis of large‐scale palaeo‐hydrological exchange stemming from glacial advance, retreat and melting during Pleistocene climate fluctuations. Furthermore, these results in conjunction with a comparison of overall faunal composition suggest that environmental differences rather than historical contingency may be responsible for the faunal dissimilarities of the Amur, Lena, and Enisei river basins.     

Analysis of genetic diversity in the endangered Hucho taimen from China

Hucho taimen are listed as endangered in China. The population size has declined recently, prompting an increase in the level of listing from grade three in 2002 to grade five in 2006. We analyzed the genetic diversity of wild populations using 17 microsatellite markers to establish a scientific basis for conservation of this species. We collected tissue samples from four populations in the Heilongjiang River basin: Huma River (HM), Hutou (HT), Haiqing (HQ), and Zhuaji (ZJ). A total of 21 loci were amplified, 18 of which were polymorphic. The number of alleles per locus ranged from 2 to 9 (mean: 4.1905). There were 13 highly polymorphic loci and 5 moderately polymorphic loci. Analysis of five genetic diversity parameters (Na, Ne, Ho, He, and PIC) suggested moderate levels of diversity within the populations. The populations were ranked HT > HQ > ZJ > HM, but the differences in diversity were not statistically significant (P > 0.05). A comparison of variation among all four populations suggested Hardy–Weinberg disequilibrium at 20% of the loci. Genetic differentiation (Fst) was 0.0644 and the gene flow among populations was estimated at 3.36 individuals per generation. The majority of diversity (93.88%) occurred among individuals within a population. In contrast, relatively little (6.12%) of the genetic diversity was distributed between the populations. An analysis of genetic differentiation and genetic distance between pairs of populations revealed that both parameters were higher in comparisons of the HM population to the HT, HQ, and ZJ populations than among the three latter populations. This suggests that the HM population has a distinct genetic structure. We hypothesize that habitat degradation and excessive fishing, not low genetic diversity, has caused the decline in H. taimen populations. However, this species should be protected from further declines in genetic diversity.     

First mtDNA sequencing of Volga and Ob basin taimen Hucho taimen: European populations stem from a late Pleistocene expansion of H. taimen out of western Siberia and are not intermediate to Hucho hucho

New concatenated mtDNA sequences (three genes; n = 22) of Siberian taimen Hucho taimen primarily from west Siberian and European regions of the species' range were added to 12 previously published sequences to provide a phylogeographic overview of the species. European samples show only very minor divergence from west Siberian populations, supporting a late Pleistocene expansion from Siberia into the Urals, with no particular relation to the Danube River basin huchen Hucho hucho as once hypothesized. The disjunct distribution of the genus is most likely based on an early Pleistocene vicariant event.