SPAWN, DIET AND IMPOSEX PHENOMENON IN THE ZIGZAG VOLUTIO ODONTOCYMBIOLA MAGELLANICA (GMELlN, 1791) (MOLLUSCA: GASTROPOOA) IN GOLFO NUEVO, PATAGONIA, ARGENTINA

BIGATTI, G.; PENCHASZADEH, P. E.

Vigo

Congreso; II Congreso lruernaciánal de las Sociedades Malacológicas Europeas,; 2002

Odontocymbio/a magellanica is a volutid snail from Potagonian shal/ow waters. Ithas a high economic potential as a natural resource. Two years of sampling by scubadiving in depths of 6-10 m were performed between 2000/2002 i~'Golfo Nuevo in orderto study the spawning secsons, diet and the imposex occurrence.o. magellanica females spcwn white, spherical, colccreous egg capsulesattcched to smal/ rocks and hard flat surfaces from July to November. Egg capsules indifferent stage.s of embryos development were found in the field from July to January.External calcium layer of the egg capsule is presumably secreted by a, calcareous glandin the snai/'s foot.Odontocymbio/a magellanica is a specialized predator on several bivclve s. notably theveneridae Venus antiqua and Eurhoma/ea exa/bida in depths -of 6-lOm. Other bivalveseaten are Au/acomya ater and Ch/amys madrynensis. Gastropods represent lowerrelevance and the most common are Tegula pataqonica, Natica isobelleano and Trophongeversianus. In a single case we found cannibalism (a large o. mage/lanica eating asmal/er individual of the same species).o. magel/anica showed between 85,7/0 and 100/0 imposex cccurrence nearharbors with low water currents (Puerto Madryn), and a Relative Penis Size Index