Role of neuropeptide F in regulating filter feeding of Manila clam, Ruditapes philippinarum

Endogenous signals which may be involved in the regulation of filter feeding in bivalves have never been examined. NPY/NPF homologue has been proved to play an important role in the regulation of food intake in vertebrate and several invertebrates. In this study, a NPF homologue was cloned from visceral ganglia of clam Ruditapes philippinarum. The full-length cDNA sequence was 892 bp in length and encoded a precursor of 82 amino acid residues. We then examined the effects of fasting and refeeding on the filtration rates (FR), plasma glucose concentration (PGC), 5-HT, DA and the expression level of the rp-NPF and insulin transcript. The mRNA expression level of rp-NPF in visceral ganglion was increased during fasting, and rose to highest level on 72 h after starvation and declined immediately after food had been supplied. Hemocoel injection of rp-NPF(5 μg/g)significantly increased FR of clams within 2 h. Compared to the controls, a significant increase in insulin mRNA levels was observed at 8 h after injection. Contents of 5-HT and DA also increased in the 5 μg/grp-NPF administrated clams at 8 and 24 h after injection. These results suggest that, similar to vertebrates, NPF, insulin, 5-HT and DA may play a role in the regulation of feeding in R. philippinarum.