Abstract:Amphioctopus fangsiao, a synonym of Octopus ocellatus in China, is one of the most important economic species in the northern coast of China. Owing to overfishing and ever-increasing market demand, the wild resources of A. fangsiao are decreasing significantly, and therefore artificial breeding is imperative. The present study on the reproduction model of A. fangsiao would provide basic data for artificial breeding and germplasm conservation of the species. In the present study, 4 groups of triplex PCR sets were established using 12 high polymorphic microsatellite markers developed in our laboratory. Through the identification of paternity of 4 female parents (♀1, ♀2, ♀3, and ♀4), 104 offspring and 19 candidate male parents of the reproduction model A. fangsiao were analyzed. The results showed that the four groups of microsatellite multiplex PCR sets worked effectively in the paternity relationship analysis, and the identification rate of 104 offspring was 94.23%. Twelve offspring and 3 males were identified in ♀1 group, and the number of offspring and males identified in the groups ♀2, ♀3, and ♀4 were 40 and 7; 19 and 2; and 27 and 4, respectively, and ♂2, ♂3, ♂7, and ♂10 mate with two or more females, which indicates that A. fangsiao is polygynandry. Polygynandry is an adaptive mechanism by aquatic animals to environmental changes and human fishing pressure. It can effectively improve the genetic diversity of alleles and bring about genetic variation among offspring. In addition, polyandry plays a positive role in maintaining the stability of the population structure of A. fangsiao, and in improving the reproductive efficiency and offspring quality. The offspring from four groups assigned to ♂2 were as high as 71.43% (10/14), 60.98% (25/41), 85.71% (18/21), and 75% (21/28), respectively, which was higher than that assigned to the other male parents. This indicates that most of the sperm involved in fertilization were from ♂2; thus, ♂2 takes advantage of sperm competition and cryptic female choice. The present study provides important data for artificial breeding and proliferation, and also for the release of A. fangsiao.
