FOOD AND FEEDING OF PAEDOCLIONE DOLIIFORMIS DANFORTH, A NEOTENOUS GYMNOSOMATOUS PTEROPOD

¹ Marine Sciences Centre and Department of Biology, McGill University, Montreal, Quebec, Canada

The neotenous gymnosome, Paedoclione doliiformis, feeds exclusively on the thecosomatous pteropods, Spiratella retroversa or S. helicina. Three prehensile buccal cones are used to capture prey; the fourth buccal cone is rudimentary. Paedoclione employs its proboscis, radula and hooks to completely extract the prey body from its shell.

Paedoclione doliiformis frequently coexists in the collection area with another gymnosome, Clione limacina, which is also a feeding specialist on Spiratella. Paedoclione and polytrochous larvae of Clione preferentially select small-sized prey of less than 1.0 mm shell diameter and thus are potential competitors for food: adult Clione feed exclusively on Spiratella larger than 1.0 mm. It is suggested that neoteny in Paedoclione permits coexistence of these two gymnosome species by limiting food competition to the small-sized, more abundant prey.