These peptides are synthesized in the x-organ (XO) and travel via axoplasmic flow to the synaptic terminals of the sinus gland (SG) where they are secreted into the hemolymph (see Hopkins, 2012, for review).
Additionally we treated intact crabs that had been transferred from 35 ppt to 15 ppt salinity with whole-eyestalk injections as well as with separate sinus gland and medullary tissue injections in an attempt to demonstrate the capacity of the eyestalk to inhibit CA induction and to determine the anatomical location of the putative hormone.
For medullary tissue (MT) and sinus gland (SG) injections, the two
Injection of isolated sinus gland (SG) homogenate harvested from 35ppt-acclimated donor crabs (SG-35 ppt) reduced CA induction significantly by 49% (P < 0.
Specifically, this CA repressor hormone is likely to be localized to the sinus gland, as SG injection caused a 49% decrease in salinity-stimulated CA activity while MT injection triggered only a nonsignificant, 22% decrease (Fig.
In conclusion, in this study we demonstrate the presence of a carbonic anhydrase repressor hormone localized to the sinus gland of the euryhaline marine crab Callinectes sapidus.