Meeting Abstract

P2.44  Friday, Jan. 4  Structure of the calcified tendons of the dactylopodite in the blue crab Callinectes sapidus CRAWFORD, E A; GAY, D M; DILLAMAN, R M*; University of North Carolina Wilmington; University of North Carolina Wilmington; University of North Carolina Wilmington dillamanr@uncw.edu

Cuticle morphology in crustaceans varies tremendously, from the thick, multilayered and calcified cuticle of the dorsal carapace to the thin, homogeneous non-calcified cuticle covering the gills. We examined the histology and ultrastructure of the blade-shaped tendons that serve as the points of attachment for the abductor and adductor muscles of the first pereopod and found that they represent still another variation in cuticle structure. Using a variety of histochemical stains and light microscopy we were able to determine that the tendon is formed by the folding of a region of the cuticle and the subsequent fusion of the apposing epicuticular layers. There are at least two layers of cuticle under the epicuticle that vary both in morphology and composition from the epicuticle. The chitin fibrils also show a unique arrangement insofar as they do not display the rotational deposition pattern of the dorsal carapace, but rather seem more longitudinally oriented. Transmission electron microscopy of the cell types adjacent to the surface of the tendon revealed both hypodermal-like cells that appear to be secreting the cuticle and microtubule-filled epidermal cells that bridge the gap between the muscle cells and the cuticle and serve to anchor the muscle fibers to the cuticle. The tendons are also partially calcified and x-ray microanalysis of the mineral indicates that they have a much higher phosphate concentration than seen in the calcium carbonate of the dorsal carapace and the tendons may therefore be a calcium phosphate containing structure.