Uric acid accumulation within intracellular crystalloid corpuscles of the midgut gland in Pomacea canaliculata (Caenogastropoda, Ampullariidae)

VEGA, I.A.; GIRAUD-BILLOUD, M.G; KOCH, E.; GAMARRA-LUQUES, C.; CASTRO-VAZQUEZ, A.

VELIGER

California Malacozoological Society

Año: 2007 vol. 48 p. 276 - 283

0042-3211

Pomacea 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. The physiological significance of uric acid storage in such specialized tissue is discussed