The Wild Resource Distribution And Population Genetic Diversity Of Leptobotia Elongata(Bleeker)

Elongate loach (Leptobotia elongate Bleeker), an endemic fish species to China, is a famous ornamental freshwater fish, which disturbuted in the upper reaches of the Yangtze River of China. The resource of Elongate loach in Yangtze River was investigated by visiting fishermen, trawling, and so on. The results showed that the Elongate loach resources in Yangtze River has rapidly decreased and at the brink of extinction.To analyze wild population structure and evaluate genetic diversity of the famous ornamental fresh water fish, elongate loach (Leptobotia elongata (Bleeker)), a comparative analysis using partial mtDNA control region (D-loop)(835bp) sequences was performed for110individuals from five localities in upper reaches of the Yangtze River, China. A total of49polymorphic sites and45haplotypes were detected, and the haplotype diversity (h) and nucleotide diversity (π) were0.952and0.00454, respectively. The overall mean genetic distance among individuals was0.0046±0.0010. The genetic distance of intra-group ranged from0.0033±.0011to0.0050±0.0012, and that between pairwise groups ranged from0.0037±0.0.0011to0.0050±0.0012. The neutral test of Tajima’s D (-1.86383, P<0.01) and Fu’s Fs (-25.92536, P<0.01), together with uni-modal mismatch distribution, indicated a recent genetic bottleneck or population expansion of the species in history. Analysis of molecular variance (AMOVA) revealed that small variances occurred among groups (1.7%), while most variances occurred within groups (98.3%). Also, there were no significant population structure (Fst=0.01702, P>0.05), and extremely high gene flows among groups (Nm=28.88), suggesting low genetic divergence in the species. It should be attribute to that the fish spawn drift eggs and the individuals migrate downstream or upstream in its distribution ranges frequently. Thus, the gene flows could frequently occur among these groups. These groups of Elongate loach distributed in upper reaches of the Yangtze River should be considered as a whole unit for management.The complete mitochondrial genome of Elongate loach was determined using pairs of conservation primers, high-fidelity PCR reaction and primers walking sequencing, which was16591bp in length. It contained13protein-coding genes, two ribosomal RNA (rRNA) genes,22transfer RNA (tRNA) genes and one control region, with an identical sequence order to that of most vertebrates.The origin of L-strand replication (OL) in Elongate loach mitochondrion was located in a cluster of five tRNA genes (WANCY region) with30nucleotides in length. The control region was925nucleotides in length,and was located between tRNA-Pro and tRNA-Phe genes. Based on the12protein-coding genes on the heavy strand of Elongate loach and other cobitidae species, the phylogenetic relationship analysis among13cobitidae species was performed by Bayesian and maximum parsimony methods. The result suggested that phylogenetic tree was divided into two branchs. Acantopsis, Pangio, Cobitis, Niwaella, Koreocobitis and Misgurnus clustered into a sub-family (cobitinae), Chromobotia and Leptobotia clustered into another sub-family (botiinae).The absolute fecundity for Elongate loach was between6160and47239, with the average of27511. The relative fecundity was between26.6and48.8particles per gram of body weight, with the average of37.7. The mixture of LRH-A2and pituitary were used to promote Elongate loach spawning, and spawing rate was75%-81.8%. The fertilization rate and hatching rate were up to82%-83%and87%-98%, respectively.