STIMULATION OF OSMOREGULATING PROCESSES IN THE PERFUSED GILL OF THE CRAB PACHYGRAPSUS-MARMORATUS (CRUSTACEA, DECAPODA) BY A SINUS GLAND PEPTIDE

Isolated posterior gills of the hyper-hyporegulating crab Pachygrapsus marmoratus were perfused with extracts of homologous sinus glands. Si nus gland extracts stimulated the influx of Na+ ions and increased the transepithelial potential difference in the gills in a dose-dependent and reversible fashion. The bioactivity of extracts prepared from cra bs that had been acclimated to 10 parts per thousand salinity for at l east 1 week was not significantly different from that of extracts prep ared from seawater (36 parts per thousand salinity) crabs. The perfusi on experiments with both extracts containing two sinus glands signifi cantly increased Na+ influx by about 150% and transepithelial potentia l difference by about 45%. Sinus gland extracts also increased the Na/K+-ATPase activity by 54% in incubated posterior gills. The bioactivi ty of extracts was reduced by pronase and trypsin, but not by healing for 10 min at 100 degrees. The molecular weight of the responsible fac tor(s) was >5000 Da. Thus, the sinus gland of P. marmoratus is conclud ed to be involved in the neuroendocrine control of osmoregulation and to contain a peptide(s) that directly influences branchial function. ( C) 1995 Academic Press, Inc.