Polymorphism of ova number in the egg case of bigfin reef squid, Sepioteuthis sp.1 ("aka-ika" type), in Tanegashima Island, Ryukyu Archipelago, Japan

Abstract

Species identification was conducted on egg masses collected from artificial spawning beds of bigfin reef squid, which were installed at 40 m depth off the coast of Tanegashima Island, Japan. Three egg masses were collected from the spawning beds. The mean number of ova of the three egg masses were 6.2 from 14 egg cases, 6.6 from 24 egg cases, and 6.0 from 30 egg cases, respectively. Phenotypic characters were identical to "shiro-ika type" Sepioteuthis sp. 2. egg cases. Interestingly, allozyme analysis indicated that the egg cases were from "aka-ika type" Sepioteuthis sp. 1, and not "shiro-ika type" Sepioteuthis sp. 2. Genetic analyses are essential to properly identify egg cases of Sepioteuthis to species level.