Mitotic arrest and toxicity in Biomphalaria glabrata (Mollusca: Pulmonata) exposed to colchicine.

Continuous exposure of Biomphalaria glabrata snails to 0.1% colchicine resulted in a significant increase, relative to non-exposed snails, in the number of arrested mitotic figures in the amebocyte-producing organ (APO) as soon as 4 h, with peak numbers after 12 h of exposure. The number of circulating hemocytes was significantly elevated at 24 h. However, by 72 h both the number of mitotic figures in the APO and the concentration of circulating hemocytes in the hemolymph had returned to control levels. Hemocytes appeared to possess normal morphology throughout this exposure, including the formation of long filopodia with supporting rodlike structures that have been reported to contain microtubules. Snail survival decreased as a function of exposure time. Significantly fewer snails, relative to controls, survived a 48-h exposure, and only 1 out of 30 snails recovered from a 72-h exposure to 0.1% colchicine. Colchicine-exposed snails displayed intoxicated behavior, even upon removal from the colchicine solution, although no histopathology was evident in the CNS of snails exposed for 72 h.