Re: Sea Hare 'Love Drug'

August 14, 2006
From: Bill Rudman

Concerning message #9364:

In that earlier message I commented on the discovery of a chemical [pheromone] in the egg masses of Aplysia californica which was named attractin because it appeared to attract Sea Hares and so cause them to aggregate and then mate.  Since then the team working on this unique pheromone have found very similar proteins in 5 other species of Aplysia and have studied the effects of A. californica attractin on these species. They have also studied the effect of an artificial hormone made of what they think is the active part of the attractin molecule.

While each species produces a slightly different pheromone, the research shows that  Aplysia californica attractin attracts species such as Aplysia brasiliana, whose attractin is chemically very similar.  They also describe attractins for Aplysia fasciata, Aplysia depilans and Aplysia vaccaria.

Interestingly the attractins fell into two structural groups, those of A. californica, A. brasiliana and A. fasciata, species which are not found together, all have very similar attractins. On the other hand, A. vaccaria, which is often found in aggregations with A. californica, and A. depilans, often found with A. fasciata, have structurally different attractin molecules. This would suggest that while any Aplysia attractin may interest any species of Aplysia, a particular species needs a species specific, or closely matching attractin molecule, to invoke mating 'closeness'.

Attractins are the first family of waterborne peptide pheromones to have been isolated and characterised in invertebrates.

• Cummins, S. F., Nichols, A. E., Rajarathnam, K., and Nagle, G. T. (2004) A conserved heptapeptide sequence in the waterborne attractin pheromone stimulates mate attraction in Aplysia. Peptides, 25: 185-189.
• Painter, S. D., Chong, M. G., Wong, M. A., Gray, A., Cormier, J. G., and Nagle, G. T. (1991) Relative contributions of the egg layer and egg cordon to pheromonal attraction and the induction of mating and egg-laying behaviour in Aplysia. Biological Bulletin, 181: 81-94.
• Painter, S. D., Cummins, S. F., Nichols, A. E., Akalal, D. G., Schein, C. H., Braun, W., Smith, J. S., Susswein, A. J., Levy, M., de Boer, P. A., ter Maat, A., Miller, M. W., Scanlan, C., Milberg, R. M., Aweedler, J. V., and Nagle, G. T. (2004) Structural and functional analysis of Aplysia attractins, a family of water-borne protein pheromones with interspecific attractiveness. Proceedings of the National Academy of Sciences, 101: 6929-6933.

Best wishes
Bill Rudman

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