Reproductive Cycle and Oviposition Events in Odontocymbiola magellanica (Gmelin, 1791) (Caeslogastropoda: Vollatidae) in Golfo Nuevo,Patagonia, Argentina

GREGORIO BIGATTI; P. E. PENCHASZADEH

Sanibel Island, Florida, U.S.A.

Conferencia; 70th Annual Meeting American Malacological Society; 2004

American Malacological Society

The voluiitl sr~ailO dor~tocyrirbiolan lagellnriicn is distributed from off  Rio de la Plata(35" S) to Chiloe Island in Southern Chile. In Atlantic waters, 0 . mngellanica is part of tlie <)~goclllnriqsp atngoriica com~nunity in depths behveen 100-1 10 m off the Province of Buenos Aires and inhabils shallow waters (5 to LO nieters depths) in the Patagonia~l~it iaral. Spawning sampling was perfonned from September 2000 lo Decer-nber :2.00:J by SCUBA diving at the locality of Playa Paranh-Punts Loola. Females spawll white, spherical, calcareous egg capsules attached to sniall rocks and hard flat si~rfaces. Spawn occurs from July to November, showing two peaks of oviposition, in coincidence with an increase in water temperature after the winter and with llie n~aximum water temperature in summer. Egg capsules in different stages of emb~.yonidce velopment were found from .My to March. Oilo~i/oc~~mOiro~l~na gellarricn is the onl) species in the family Volutidae known to have an external calcium layer on the egg capsule. The egg capsule is secreted by a gland located in the anterior portion of the snaii fool. It is spherical, with a mean diameter of 30 mm. The uncleaved egg dian~eter varies between 212-24.0 lm. A total of 4-8 embryos develop in each egg capsule, consunling nutritive substances in tlie intracapsular liquid. Hatching occurs at tlie c~.awlingst age, with a shell length of 8-1 1 mm. Observations of histological slides shown an oocyte diameter increasing from 55.5 Lim in June to 150 kim in November. Coprlation stasis approximately one niontli before the first oviposition event.O dor~tocyrirbiolan lagellnriicn is distributed from off  Rio de la Plata(35" S) to Chiloe Island in Southern Chile. In Atlantic waters, 0 . mngellanica is part of tlie <)~goclllnriqsp atngoriica com~nunity in depths behveen 100-1 10 m off the Province of Buenos Aires and inhabils shallow waters (5 to LO nieters depths) in the Patagonia~l~it iaral. Spawning sampling was perfonned from September 2000 lo Decer-nber :2.00:J by SCUBA diving at the locality of Playa Paranh-Punts Loola. Females spawll white, spherical, calcareous egg capsules attached to sniall rocks and hard flat si~rfaces. Spawn occurs from July to November, showing two peaks of oviposition, in coincidence with an increase in water temperature after the winter and with llie n~aximum water temperature in summer. Egg capsules in different stages of emb~.yonidce velopment were found from .My to March. Oilo~i/oc~~mOiro~l~na gellarricn is the onl) species in the family Volutidae known to have an external calcium layer on the egg capsule. The egg capsule is secreted by a gland located in the anterior portion of the snaii fool. It is spherical, with a mean diameter of 30 mm. The uncleaved egg dian~eter varies between 212-24.0 lm. A total of 4-8 embryos develop in each egg capsule, consunling nutritive substances in tlie intracapsular liquid. Hatching occurs at tlie c~.awlingst age, with a shell length of 8-1 1 mm. Observations of histological slides shown an oocyte diameter increasing from 55.5 Lim in June to 150 kim in November. Coprlation stasis approximately one niontli before the first oviposition event.