Meeting Abstract

P2.124  Sunday, Jan. 5 15:30  Structure of the meso- and urocardiac ossicles of the blue crab, Callinectes sapidus – molt dynamics and aging ROER, R; VATCHER, H*; DILLAMAN, R; Univ. of N.C. Wilmington; Univ. of N.C. Wilmington; Univ. of N.C. Wilmington roer@uncw.edu

The ossicles of the cardiac stomach of decapods are cuticular structures employed to grind food particles. A recent paper (Kilada et al., 2012) suggested that bands observed in sections of the mesocardiac ossicle in snow crabs, lobsters and shrimp corresponded to the age of the individuals. The present study examined the structure of the meso- and urocardiac ossicles of the blue crab to assess its utility in age determination. The ossicles, for the most part, bear a structural similarity to that of the calcified dorsal carapace. Staining with acridine orange showed the same arrangement of an epi-, exo- and endocuticle. In much of the meso- and urocardiac ossicles, the endocuticle is very reduced, with the exocuticle predominating; the reverse of the dimensions of the exoskeleton. The lamellate structure of the ossicles was confirmed with scanning electron microscopy. However, elemental mapping by energy-dispersive analysis of X-rays (EDAX) revealed that the ossicles are mineralized with calcium phosphate, in contrast to the calcium carbonate biomineral of the exoskeleton. The posterior tooth of the urocardiac ossicle is predominantly organic, not calcified but presumably heavily sclerotized. It also contains appreciable amounts of silicon. Histological examination of the ossicles demonstrated that they are molted during ecdysis, so despite the appearance of bands in the mesocardiac ossicle, it is difficult to hypothesize how these bands could represent a record of chronological age. This work was supported by funds from NC Sea Grant.