Marked changes in neuropeptide expression accompany broadcast spawnings in the gastropod Haliotis asinina

We demonstrate that genes encoding APGWamide, myomodulin, the putative proctolin homologue whitnin, FMRFamide, a schistosomin-like peptide (SLP), a molluscan insulin-related peptide (MIP) and a haliotid growth-associated peptide (HGAP) all are differentially expressed in the anterior ganglia during the two week spawning cycle in both male and female abalone. Each gene has a unique and sex-specific expression profile. Despite these differences, expression levels in most of the genes peak at or within 12？h of the spawning event. In contrast, lowest levels of transcript abundance typically occurs 36？h before and 24？h after spawning, with differences in peak and low expression levels being most pronounced in genes orthologous to known molluscan reproduction neuromodulators.Exploiting the predictable semi-lunar spawning cycle of the gastropod H. asinina, we have identified a suite of evolutionarily-conserved, mollusc-specific and rapidly-evolving neuropeptides that appear to contribute to the regulation of spawning. Dramatic increases and decreases in ganglionic neuropeptide expression levels from 36？h before to 24？h after the broadcast spawning event are consistent with these peptides having a regulatory role in translating environmental signals experienced by a population into a synchronous physiological output, in this case, the release of gametes.The Mollusca is an extraordinarily diverse and successful phylum whose members occupy a wide range of terrestrial, freshwater and marine habitats. In the marine environment, molluscs currently account for approximately 23% of the 230,000 known animal species, a proportion rivalled only by the Crustacea [1], and it is estimated that over 50% of extant molluscs still have yet to be discovered and described [2]. The success of marine molluscs can be attributed partially to their varied modes of reproduction, which range from synchronous broadcast spawning entrained by environmental cues (e.g. chitons, bivalves and gastropods) t