Abstract
Biologically active peptides play critical roles in regulating a wide range of physiological processes as neuropeptides, hormones and pheromones. Our knowledge of bioactive peptides in molluscs is expanding rapidly due to the introduction of next-generation nucleotide sequencing, sensitive mass spectrometry methods and developments in bioinformatics. It has been predicted that up to 200 different peptides may be present in any one species. Neuropeptides, which are peptides secreted from neurons, tend to be well conserved throughout evolution, indicating their critical role as regulators of physiological and behavioural processes such as development, reproduction, maintenance of growth and metabolism. In molluscs, neuropeptides may also be secreted from haemocytes, glands or endocrine cells. This presentation will provide an overview of our current understanding of those neuropeptides in molluscs that have a welldefined function, such as the egg-laying neuropeptide that triggers egg-laying in gastropod molluscs, and possibly others. Many neuropeptides identified have less distinct roles but we are gaining greater understanding of these through analysis of gene or protein expression, receptor characterisation and targeted peptide interference. For example, using the snail as our model, differential gene expression studies are showing that certain neuropeptides may regulate their ability to hibernate or aestivate, a state of extreme hypometabolism that ensures life may continue even during periods of difficulty. Peptides may also be secreted from the mollusc and have bioactivity as animal-animal signaling molecules; examples include peptide pheromones that regulate sea slug attraction, squid aggression, abalone aggregation, oyster spawning, freshwater snail ovoposition and terrestrial snail sperm storage. Such is the significance of bioactive peptides in almost every aspect of molluscan physiology, they provide excellent candidates for which to develop of mimetic therapies that could enhance aquaculture and eliminate invasive pest species.