Abstract:Octopus ocellatus, affiliated to Octopodidae under the phylum Mollusca, is one of the most important economic species along the northern coastal areas of China. It has been considered as a candidate for aquaculture enhancement and release owing to its short life span and rapid growth. However, little is known about sexual selection before and after copulation in this species. To explore the mechanism of sexual selection in O. ocellatus, 11 morphological parameters of 36 adult octopuses were first measured and analyzed. Afterwards, 14 polymorphic microsatellite DNA markers were used to identify the paternity of 176 offspring and 3 female and 17 male parent candidates. The morphological parameters of male parents with and without offspring and those with high and low proportion of offspring were analyzed in three families by the t-test. The genetic similarity between female and male parents which had high and low percentage of offspring was also calculated. The results showed that there was a strong correlation between mantle length, wrist 2, wrist 6, and body weight in male octopuses, and that sexual dimorphism in the total weight and mantle width between male and female octopuses existed. Paternity testing revealed all three females mated with more than two males and 10 males mated with at least two females, which confirmed the polygyny and polyandry pattern in this species. There was no correlation between male octopuses with or without offspring and their morphological parameters. Moreover, the proportion of offspring was not related to the morphological parameters of males but was correlated to the genetic similarity and genetic distance between female and male parents—higher the genetic similarity, higher the proportion of offspring. This study provides a scientific basis for the resource protection and artificial breeding of O. ocellatus, and also, important information for research on the mechanism of sexual selection in marine cephalopods.
