Studies On Population Genetics Of Octopus Minor Located In The Waters Of China

Octopus minor is a kind of commercially important cephalopod in the waters ofChina. Due to its high nutritional value, it is very popular with consumers. Wildpopulations of O.minor have been declining in recent years because ofover-exploitation. At present, there are still few research reports about populationgenetic diversity and genetic structure of the species located in Chinese waters. In thispaper, ten wide geographic populations (334individuals) were collected from Dalian,Laizhou, Yantai, Rongcheng, Ganyu, Shengsi, Nanji Island, Lianjiang, Quangang andYilan located in the Bohai Sea, Yellow Sea, East Sea as well as Taiwan, respectively.The population genetic structure and diversity of O.minor were analyzed based onmultivariate analysis methods of morphological measurements and microsatelliteDNA markers. The main results of this study are summarized as follows:Morphological measurements indicated that the arm formula of O.minor was1>2>3>4and the web formula was A> B> C> D>E. The correlation relationshipsamong body length, weight, mental traits and funnel traits reached significant levels.Principal component analysis constructed two main components. The cumulativecontribution rate was up to97.090%, indicating that it was suitable for O.minor toexplain difference between different populations with several independent factors. Tendiscriminant functions were established based on stepwise discriminant analysis andoverall discrimination accuracy was70.1%which was ideal. YL could be clearlyseparated from the other populations based on scatter plots of discriminant functions.Also it could separate the southern from the northern populations. ANOVA analysisshowed that: there was no significant difference in the number of suckers between DL,LZ, YT and YL populations. The number of suckers was very close between GY and RC and also between NJD and QG. SS and LJ had the most suckers and revealedsignificant difference with other populations. Ten populations were clustered into twocategories: five northern populations (DL, LZ, YT, RC, GY) and four southernones(SS, LJ, NJD, QG), while YL was clustered together with northern populations.Genetic diversity and population structure of ten O.minor geographic populations inChinese waters were investigated with microsatellite DNA markers. Eightmicrosatellites revealed high allelic diversity with11-26alleles per locus. Observedand expected heterozygosity varied from0.412to0.900and from0.337to0.845,respectively. Pairwise Fstvalues indicated that genetic differentiation amongpopulations had reached a significant level and the total Fstvalue was0.198,indicating a great genetic differentiation among populations. The Fstvalue of YL wasup to more than0.3and its degree of differentiation may reached the level ofsubspecies. Results of AMOVA analysis revealed that most of the variance wasdistributed within populations (70.006%). Variance between groups (14.551%) andamong populations within groups (15.443%) also reached significant level. Manteltest showed significant correlations between genetic distance and geographicaldistance (R=0.383, P=0.004) indicating that genetic differentiation of O.minorconformed to a pattern of isolation-by-distance. Cluster analysis usingneighbor-joining divided nine populations into three groups and divided tenpopulations into two groups while YL was distinguished from the others. Bayesiananalysis also showed the difference between southern and northern populations andYL showed larger similarities with northern populations especially with GY. Theresults demonstrated the consistency with morphological analysis. Analysis based onFst, Dcvalue and clustering showed the heterogeneity of YL and the relativehomogeneity between YL and GY. The significant population genetic structure ofO.minor was related to the combined effects of geographical barriers, current featuresand life history characteristics.