| Epinephelus awoara belongs to the Perciforme,Epinephelidae,Epinephelus[1],and is one of the important economic fish.In recent years,the size and resources of wild E.awoara have declined,because of overfishing and environmental pollution.However,at this stage,the research of E.awoara is mainly focused on breeding technology,diseases,etc.There is still a lack of systematic research and combing in basic biology learning and population genetics.In this study,we conducted systematic observations on the basic biological learning of the three wild populations(MN,DYW,BBW),such as growth regularity and gonadal development,in order to investigate whether the wild grouper resources have evolved adaptively under the influence of intense human activities recently.At the same time,we conducted a systematic population genetics study on the three wild populations by using three techniques of sequence analysis of mitochondrial and nuclear genes,microsatellite molecular markers and RAD-seq technology.Tha aim was to provide basic reference materials and information for the protection,artificial breeding and related fishery policy of the existing wild resources of awara.The main conclusions of this paper were as follows:1.The relationship between the body length and weight of female and male E.awoara was:W♀=8E-5L2.7961;W(?)=2E-5L3.0028,indicating that females growed at a heterogeneous rate and males growed at a uniform rate.The growth rate of the Minnan population was significantly higher than that of the Daya Bay population,which was presumed to be greatly influenced by environmental factors such as nutrition.In the study of the reproductive habits of E.awoara,the characteristics of different gonadal development patterns were compared.The histological characteristics of oocytes and development of ovarian and sperm nests at different stages were described in detail.Through the observation of the slices,it was found that no oocytes appeared in the gonads after the fourth stage of the testis.It was histologically verified that the male individuals of E.awoara would not undergo the sex reversal process from male to female.Compared with the 1980 data,the highest peak of the maturity coefficient was also from May to June,whitch it was also found that the samples collected in the Daya Bay waters matured in early May(22～25℃),whitch was earlier than the samples collected in Zhejiang at the same period in 1980(21～23℃).It was speculated that the development of gonads and ovulation behavior were greatly affected by water temperature.At the same time,it was found that the GSI value and egg diameter of each stage of the ovary generally declined.It was speculated that the E.awoara populations may had undergone some adaptive evolution due to the impact of overfishing and environmental pollution.In addition,the detection of male E.awoara in this study further supportted the inference that the appearance of primary male grouper samples may be related to the growth environment.2.The genetic diversity and the historical dynamics of three wild populations of E.awoara(MN,DYW,BBW)were analyzed.A total of 56 haplotypes and 97 polymorphic loci were defined,Ts/Tv=5.1.The haplotype diversity(Hd)ranged from 0.889 to 0.980,and the nucleotide diversity(π)ranged from 0.00327 to 0.00404,showing high Hd and low π values.The nuclear gene RyR3 detected 5 alleles,8 polymorphic loci,Ts/Tv=1<2,indicating that the RyR3 gene sequence had reached mutation saturation.The allele frequency was 0.000～0.078.The nucleotide polymorphism(π)was between 0.00000 and 0.00011.The results based on microsatellite markers showed that Ho and He were 0.562 and 0.603;PIC ranged from 0.463 to 0.636.The results based on RAD-seq showed that Ho was between 0.025～0.122,and Hs was between 0.165～0.183.The above results indicated that although the E.awoara had been affected by a certain degree of human interference,the current genetic diversity of its wild populations was still at a moderately high level.3.The above three techniques had similar conclusions on the genetic structure of three grouper wild populations.AMOVA analysis showed that the genetic variation of E.awoara were mainly within the populations.The results of the three technologies were slightly different in terms of population differentiation level.The genetic differentiation index FST value was 0.000～0.001 based on RAD-seq,indicating that no significant differentiation among the three populations.Based on the results of mitochondrial sequencing,the FST value was between 0.00505～0.09939,which showed that only the BBW population and the MN population had a low degree of differentiation.Based on the analysis of microsatellite markers,the FST range was from 0.043 to 0.091,which showed that in addition to the MN group,the BBW group also had low differentiation with the DYW population.It may be related to the number of samples detected and the difference in sensitivity of different methods,but it still suggested that the hydrological characteristics of the Qiongzhou Strait may had a certain effect on the genetic communication between the grouper populations on both sides of the Strait.In addition,the haplotype network diagram showed that there was no significant geographic lineage structure in the three populations.The nucleotide mismatches distribution showed a unimodal distribution,which was consistent with the model of the population expanding after experiencing the bottleneck effect.Finally,based on the above research results,this article put forward protective suggestions in terms of improving the environment of the E.awoara habitat,strictly controlling the fishing intensity,promoting artificial breeding techniques and conducting resource research. |
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