Résumé
Isolated posterior gills of the hyper-hyporegulating crab
Pachygrapsus marmoratus were perfused with extracts of homologous sinus glands. Sinus 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 crabs that had been acclimated to 10% salinity for at least 1 week was not significantly different from that of extracts prepared from seawater (36% salinity) crabs. The perfusion experiments with both extracts containing two sinus glands significantly increased Na
+ influx by about 150% and transepithelial potential difference by about 45%. Sinus gland extracts also increased the Na
+/K
+-ATPase activity by 54% in incubated posterior gills. The bioactivity of extracts was reduced by pronase and trypsin, but not by heating for 10 min at 100°. The molecular weight of the responsible factor(s) was > 5000 Da. Thus, the sinus gland of
P. marmoratus is concluded to be involved in the neuroendocrine control of osmoregulation and to contain a peptide(s) that directly influences branchial function.