Temporal variation in microstructure of the inner shell surface of Corbicula Fluminea (Bivalvia: Heterodonta)

Temporal variation of shell microstructure with emphasis on the inner shell surface was examinedin caged and noncaged Corbicula flurninea (Muller) from the Leaf River, Mississippi. Shell structurein the outer shell layer, overlain by the periostracum, exhibited distinct seasonal variation from crossed lamellarin warmer months to structures resembling cone complex crossed-lamellar in cooler months.Other variations associated with season were subtle, involving only the inner shell surface microstructures,such as replacement of well developed lamellae in warmer months by pitted, deformed or reticulatemicrostructures in cooler months. The shell microstructure ventral to the pallial line is of possible usein taxonomic and phylogenetic analyses of the Corbiculacea and could also be of value as an environmentalmonitor because the microstructures in this region were less variable than those dorsal to the pallial line.