“Polyploid cells containing an endocyanobiont in the midgut gland of the applesnail Pomacea canaliculata”.

CUETO JA.; VEGA IA.; E KOCH.; A CASTRO-VAZQUEZ

San Luis, Argentina

Congreso; XXIV Reunión Anual de la Sociedad de Biología de Cuyo; 2006

Sociedad de Biología de Cuyo.

146. POLYPLOID CELLS CONTAINING AN ENDOCYANOBIONT IN THE MIDGUT GLAND OF THE APPLESNAIL Pomacea canaliculata Cueto JA, Vega IA, Koch E, Castro-Vazquez A. Lab. of Physiology, IHEM (FCM/UNCuyo-CONICET), Mendoza Argentina. E-mail cueto.juan@fcm.uncu.edu.ar Pomacea canaliculata (Caenogastropoda, Ampullariidae) is a South American freshwater snail which lodges a cyanobacterium in epithelial cells of its midgut gland. Two morphotypes of this cyanobacterium (identified as C and K morphs) are each one associated to a specific epithelial cell type in the gland. C morphs are contained within “columnar”, probably digestive cells bearing regular size nuclei, while the K morphs are associated to “pyramidal” cells bearing large nuclei, with two or more nucleoli, and a conspicuous development of the rough endoplasmic reticulum. Electron microscopy studies suggested that pyramidal cells contribute to the generation of the thick protein cover of K corpuscles. In the current work we wanted to establish if the larger nuclear size might be indicating a greater ploidy of pyramidal cells, which may mean a larger extent of protein expression by these cells. Squash, paraformaldehyde-fixed preparations of adult glands were subjected to the Feulgen reaction to establish, through image cytometry, the relative DNA quantity present in the different nuclei. The obtained histograms showed the existence in the midgut gland of P. canaliculata of several cell populations with different DNA-ploidy (2, 4, 8 and 16 C). Polyploid nuclei (i.e., those showing either 4, 8 or 16 C) where the larger ones, and with prominent nucleoli. Feulgen- treated embryos’ squashes also indicated definite polyploid cells populations, i.e., at a time when K corpuscles have not yet colonized the midgut gland.