A study of corpuscular DNA and midgut gland occupancy by putative symbiotic elements in Pomacea canaliculata (Caenogastropoda, Ampullariidae).

VEGA IA, GAMARRA-LUQUES C, KOCH E, BUSSMAN LE & CASTRO-VAZQUEZ A.

SYMBIOSIS

Balabán

Lugar: Filadelfia; Año: 2005 vol. 39 p. 37 - 45

0334-5114

Abstract Morphology of C and K corpuscles in the midgut gland of Pomacea canaliculata has suggested they may be the vegetative and cystic forms (respectively) of a prokaryotic symbiont. The corpuscles were isolated from midgut gland tissue to (1) quantify gland occupancy in different experimental conditions and (2) determine the presence of DNA in them. C and K corpuscles occupied 8.2 - 11% of the gland, and this percentage did not vary significantly according to sex or diet (a mixed diet or a paper-only diet during eight weeks). DNA was detected in both C and K corpuscles. DNA content in C corpuscles was estimated as 57 fg/corpuscle which is moderately above the range of known prokaryotic genome sizes. Determination of the DNA/protein ratio in lysates of C corpuscles yielded values similar to those of bacterial cells used as controls (Escherichia coli, Synechococcus sp.). The DNA/protein ratio in K corpuscles, however, was much lower than in C corpuscles, probably owing to the high protein content of the envelop of K corpuscles. The current results confirm the view that the corpuscles may be morphs of a prokaryotic symbiont and not ingested modified chloroplasts, as it is known in Elysiidae.