スルメイカの熟度に関する研究-III

Abstract

In some species of squids, it had been found out that the exhaustion of their generative activities after copulation and spawning leads to death. With the intention of expressing numericaly the maturation and exhaustion of the common squid, Todarodes pacificus STEENSTRUP, the present report deals with weight changes of body, liver, and genital organs in relation to the maturity condition that was proposed in the first report. The materials used were composed of autumn-spawned squids caught in the southwestern part of the Japan Sea, during November 1968 to October 1970. The results obtained are summarized as follows: 1. Exhaustion could be first seen by the loss of liver weight and subsequently by the loss of body weight. The emaciation of genital organs could be noticed at the final stage of exhaustion. 2. In males, following copulation loss in liver weight was substantial and the livers in the spent stage (0.85 in maturity condition) were exhausted to the extent that their weights were less than a quater of those in the immature stage (0.15 in M). Females also showed reduction in their liver weights after copulation (0.25 in M) but they soon regained it (0.35 in M). Nevertheless, spawning made them lose liver weights once again (0.75 in M). 3. The influence of copulation and spawning on body weight was so severe that the consumption of reserved nutrients in the liver and other body substances was hardly adequate and led the squid to death by general prostration, while retaining some spermatophores in Needham's sac (male) or eggs in oviducts (female) not spawned out.