Chemosensory communication in the New Zealand rock lobster Jasus edwardsii (Hutton) (Decapoda, Palinuridae)

Abstract

Evidence has accumulated that in decapod crustaceans chemical signals (pheromones) are released with the urine through the nephropores on the ventral base of the second antenna and that these affect behaviour associated with agonistic interactions as well as with courtship and mating. Research has mainly focused on solitary living species such as clawed lobsters and crabs which tend to be highly aggressive towards their peers. Little is still known about the importance of pheromones for the social life of the highly gregarious Palinuridae (spiny lobsters). This thesis had therefore the two major aims to determine if the New Zealand spiny lobster Jasus edwardsii also releases pheromones with the urine and if so, what role chemosensory communication may play especially during the short reproductive season in autumn. A catheterisation method had to be developed to allow for urine collection without interfering unduly with the behaviour of the animals. I found that mature females were then able to distinguish the urine of male and female conspecifics, suggesting that sex pheromones are indeed contained in the urine. Further investigations determined that aggregation pheromones are released by subadults and that production of sex pheromones only starts once maturity is reached. Investigations on the effects of abiotic and biotic factors like temperature, salinity, feeding and the lobster's moult stage were fixther necessary to establish if the outcome of studies on urine-based chemosensory communication may be modified by these factors. Since chemoreceptors on the antennules are responsible for the detection of pheromones, scanning electron micrographs were taken of these structures and their morphology was compared with the receptors of other Palinuridae, enabling better comparison of behavioural studies on other species. The thesis then focused on the role of pheromone release and detection during the reproductive period. In summary, chemosensory communication is used by J. edwardsii but does not seem to play as crucial a role as for example in the clawed lobster Homarus americanus, where the prevention of olfaction has been shown to have dramatic results especially during reproduction. It is hypothesised that the observed differences in chemosensory communication are a consequence of different population structures, social life and mating strategies of the different species.