ROER, R.D.*; TOWLE, D.W.; Univ. of N.C. at Wilmington; MDI Biological Laboratory, Salisbury Cove, ME: Temporal expression of Ca-ATPase in the hypodermis of the blue crab, Callinectes sapidus, during late pre- and early postmolt.

Previous studies provided physiological and histochemical evidence for the presence of Ca-ATPase in the hypodermis that underlies the calcifying regions of the exoskeleton of crabs. Physiological data suggested that the Ca-ATPase is involved in premolt resorption and postmolt deposition of CaCO₃ in the cuticle. The present study sought to determine if there is upregulation of Ca-ATPase precedent to or coincident with the onset of postmolt mineral deposition in the blue crab, and to determine if the expression of Ca-ATPase is restricted to hypodermal tissue involved in mineralization. RNA was extracted from the hypodermis underlying both the dorsal carapace (calcifying) and arthrodial membrane (non-calcifying) of pre- and postmolt crabs at specific time intervals. Following reverse transcription, the first-strand cDNA was subjected to semi-quantitative PCR using C. sapidus-specific primers for plasma membrane Ca-ATPase (PMCA) and arginine kinase (AK), the latter being used as a constitutively-expressed control. Data revealed very low levels of expression of PMCA during late premolt and during the first 2h postmolt. There was a marked increase in PMCA expression in both tissues at 3h postmolt, reaching a maximum at 4-6h, and then declining by 48h. Upregulation of PMCA coincides with the first observation of amorphous CaCO₃ and just precedes that of calcite in the cuticle. This work was supported by award IBN 0114597 from the NSF and a MDIBL New Investigator Award to RDR.