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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.

Mouthpart and foregut structure indicates that Jasus edwardsii phyllosomas ingest soft fleshy foods such as gelatinous zooplankton. Mouthpart morphology changes little during larval development, indicating that ingestive capabilities and external mastication are well developed from an early age. However, the density and complexity of setation and robustness of individual mouthparts increases with age, suggesting a greater capacity to ingest larger prey during development. The foregut consists of a single chamber with a number of well-developed grooves, ridges, and setae but lacking a gastric mill. The primary role of the foregut is mixing, sorting, and filtering particles, preground by the mouthparts. Phyllosomas have been divided into early (stage I-III), mid (IV-V), and late (VI-X) stages based on the development of the filter press and main brushes. Increasing robustness of setation and complexity of the foregut suggest that the texture of prey becomes more muscular (fibrous) with larval development. The results presented here suggest that early-stage phyllosoma would benefit from a diet comprising soft gelatinous items, whereas late-stage phyllosomas are better prepared to deal with larger, fleshy prey. The changes in structural characteristics with age should also serve as a guide in the development of formulated diets.

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