Development of the proventriculus in larvae of the slipper lobster, Ibacus ciliatus (Decapoda: Scyllaridae)

The morphological development of the proventriculus in the phyllosomal and nisto stages of the scyllarid slipper lobster is described and illustrated. Possible flow pathways of food particles is deduced from the structure of the proventriculus. Through all phyllosomal stages, no gastric teeth or cardio-pyloric valve are found, the proventriculus consisting of a straight tube in sagittal views. A series of grooves, spines, setae and brushes are found, and the posterior filter-press is well-developed except in newly hatched (1 st stage) larvae. It is concluded that the major function of the phyllosomal proventriculus is the filtering of food particles previously masticated by the mouthparts. By contrast, the proventriculus in the nisto stage is very different from that of the phyllosoma, being similar to that of adult lobsters. The proventriculus in the nisto stage is divided into two principal chambers (the anterior and posterior) by the cardio-pyloric valve which is formed from folds in the wall. This valve is absent from the phyllosomal proventriculus. On the other hand, in the nisto, the lateral teeth, spines, setae, grooves and filter-press are less developed than those of the phyllosomal stage. Similarly, the chitinous wall is un-calcified, and thus calcified gastric teeth are absent from the proventriculus of the nisto. These results suggest the absence of phyllosoma-like filtering and the development of juvenile/adult masticating functions in the proventriculus of the nisto. Dietary changes would therefore be expected to occur when the planktonic phyllosoma larvae metamorphose into the nisto stage, which is transitional between the planktonic phyllosoma and the benthic juvenile.