Embryonic Development of the Squid, Illex illecebrosus , and Effect of Temperature on Development Rates

Abstract

Development stages for artifically fertilized and naturally spawned eggs of II/ex illecebrosus were observed and a staging scheme proposed which relates to earlier studies on naturally spawned eggs of IIlex coindetii and artifically fertilized eggs of Todarodes pacificus. Photographs and descriptions of stages provide a reference for embryonic development of small ommastrephid eggs and an aid to the identification of egg masses of the species in nature, an essential step in understanding its life cycle. Embryonic development in I. il/ecebrosus fails at temperatures below 12.5° C, and the development rate at 21° C is nearly twice that at 12.5° C. This temperature requirement restricts the spatial and temporal distribution of spawning in this squid, and temperature-related development rates allow prediction of the age of egg masses found in nature in water masses of a particular temperature.