Useful Techniques for Artificial Fertilization of the Ommastrephid Squid Illex argentinus

概要

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This study examined the rate of fertilization in the Argentine shortfin squid <I>Illex argentinus</I> after artificial insemination using sperm from different sources, as well as the effect of cold-storage on the fertilization capacity of gametes from mature squids, and the impact of mechanical agitation on embryonic development. In addition, the process of chorionic expansion during the course of embryonic development was also examined. High fertilization rates were obtained from spermatophores (76-95%) and spermatozoa from the vas deferens (73-87%), but no fertilization was observed using spermatozoa from testes. Female and male gametes stored at 0°C had a high fertilization capacity (>72%) within 24 h. Embryos (stages 4 to 17; 3 to 61 h at 20°C) subjected to mechanical agitation at a critical period (stages 5 to 12; 5 to 20 h at 20°C) exhibited high mortality and abnormal development. In the course of embryonic development, the chorion expanded four times: once at fertilization and then at developmental stages 15-16, 17-21, and finally at stages 25-27. The growth rate of the third expansion corresponded with an increase in embryonic body length. To improve the fertilization rate and increase the production of healthy paralarvae in on-board experiments, factors such as the origin of spermatozoa, gamete storage methods, and the handling of fertilized eggs during the critical period should be carefully controlled.