Further observations on the antennal receptors of rock lobsters and their possible involvement in puerulus stage navigation

Abstract

This report examines aspects of internal and external structure of lobster larvae and juveniles. We examined the external morphology of the antenna of some phyllosoma and of a series of post‐puerulus moult stages in several species of rock lobster from different localities (Jasus edwardsii, New Zealand; Jasus novaehollandiae (=7. edwardsii), Victoria, Australia; Panulirus cygnus, Western Australia) with particular reference to the hypothesis that pueruli are morphologically specialised for direction finding (Phillips and Macmillan, 1987). We also examined the internal morphology of the antenna in the puerulus of Panulirus cygnus to see if the internal morphology could support the conclusions of the earlier scanning electron microscope study. We found that externally, the sensory equipment of the puerulus stage is essentially that of the later benthic stages. The internal structure is also the same in puerulus and post‐puerulus stages of Panulirus cygnus. The spines and pinnate setae, which previous studies suggest have some mechanosensory function, are closely similar in internal structure but with an innervation pattern that does not appear to conform to that described from other crustacean mechanoreceptors systems. While the results do not disprove the vibrational navigation hypothesis they weaken the force of the main argument in its favour: that the puerulus stage is uniquely equipped for vibrational sensitivity. Our results indicate a need for further field information on the behaviour of pueruli and leave the matter of puerulus navigation unresolved.