Carapace repair in the green crab, Carcinus maenas (L.).

Formation of a circular hole 8-10 mm in diameter in the calcified layers of the carapace from crabs in stage C of the molt cycle stimulates the tissue under and adjacent to the injury to deposit a unique calcified cuticular material below the intact membranous layer. Deposition was followed for 69 days using light microscopic histology, histochemistry, and scanning electron microscopy. Quantitative analyses of CaCO were conducted using atomic absorption spectrophotometry and Gran titration. Spatial distribution of CaCO was determined with X-radiography. A scab is formed by day two under the injury. At four days the epithelium changes from squamous to columnar and deposits a PAS-positive layer with an irregular lamellar fine structure, followed by highly organized lamellae structurally similar to normal exocuticle. Histochemically, however, these lamellae resemble normal endocuticle. CaCO is evident external to the outermost lamellae by day eleven as a fused mass of aragonite granules. The lamellar region calcifies proximally from the outer surface and is amorphous CaCO . Repair cuticle is approximately 20%CaCO by weight.