Mouthpart and foregut ontogeny in phyllosoma larvae of the spiny lobster Jasus edwardsii (Decapoda; Palinuridae)

Abstract

The mouthparts and foregut structure of 10 stages of spiny lobster (Jasus edwardsii) phyllosoma were described using scanning electron microscopy and resin histology to investigate developmental morphology and its implications for diet. Mouthpart and foregut structure indicate that J. edwardsii phyllosoma ingest soft fleshy foods such as gelatinous bodied 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, pre-ground by the mouthparts. Phyllosoma have been divided into early (stage I-III), mid (IV-V) and late (VI-X) stages based on the level of development of the filter press and main brushes. Increasing robustness of setation and complexity of the foregut suggests that the texture of prey becomes more fibrous with larval development. The results presented here suggest that early stage phyllosoma would benefit from a diet comprising soft gelatinous items, while late stage phyllosoma 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.