Neural development in the planktonic and early benthic stages of the palinurid lobster Jasus edwardsii

Jasus edwardsii has eleven phyllosoma larvae that are morphologically adapt ed for a planktonic existence. These are followed by a puerulus stage which , although it has the general body form of the adult, is also adapted for s wimming. The next moult is the first of the truly benthic juvenile stages. Using transmission electron microscopy we compared transverse sections of c onnectives in the ventral nerve cord of the first phyllosoma, the puerulus and the first post-puerulus stage at a number of points. We found that the anterior cord of the phyllosoma has approximately the same number of neuron s as the puerulus. This has implications for our understanding of crustacea n larval sensory systems because previous work shows that most fibres in th e adult nerve cord are sensory. Fibre counts in the post-puerulus increase in the expected manner. The cord structure of the puerulus and post-puerulu s is the same as that found in the adult whereas that of the early phylloso ma is not.