Characterization of intracellular crystalloid bodies in the midgut gland of the ampullariid snail Pomacea canaliculata.

GIRAUD BILLOUD, MAXIMILIANO; VEGA, ISRAEL A; CASTRO-VAZQUEZ, ALFREDO

San Luis

Congreso; XXII Reunión Científica Anual de la Sociedad de Biología de Cuyo.; 2004

Sociedad de Biología de Cuyo

P. canaliculata shows sleeves of a specialized tissue surrounding arteries of the midgut gland. This tissue is formed mainly by “radiated cells” (large vacuolated cells, bearing small nuclei without nucleoli) which are arranged around the vascular muscular layer. Smaller “satellite cells”, with a scarce cytoplasm and clear nucleolated nuclei, are found together with some nerve endings and muscle fibers on the external surface of these sleeves. Radiated cells are full of crystalloid spheres (about 5 µm diameter) showing a complex inner fibrillar structure. Crystalloid corpuscles, and pigmented C and K corpuscles present in midgut gland alveoli, were isolated from gland homogenates. Uric acid, urea, ammonia, protein and calcium were determined in both gland homogenates and corpuscular fractions. Uric acid was the major non-protein nitrogen compound of the midgut gland and was concentrated in crystalloid corpuscles (accounting for 53% of corpuscular dry mass), but was not detected in pigmented corpuscles. Calcium accounted for only 0.6% of crystalloid dry mass. Protein was another significant component of crystalloid bodies (32% of dry mass). Ammonia, followed by urea, was the main nitrogen excretory product in the soluble fraction of excreta, while protein predominated in the particulate excretory fraction. Uric acid stored in such specialized tissue may serve as a free radical scavenger and antioxidant compound, a function that may be particularly important when the snail arises from seasonal dormancy.