Studies on Volutids in Argentina (Caenogastropoda: Volutidae)

PENCHASZADEH, P. E.; ARRIGHETTI, F.; CLEDÓN, M.; BIGATTI, G.; GIMÉNEZ, J.; LUZZATTO, D.; SÁNCHEZ ANTELO, C.

Sunibel Island, Florida. USA

Congreso; 70th Annual Meeting American Malacological Society; 2004

Adelomelon brasiliana (Lamarck, 1811) specimens were captured monthly in the Mar del Plata area (15m depth) during three consecutive years. The reproductive season extends from September to April. The mature oocytes reach 200 ìm in diameter before spawning. In autumn, a resting phase begins, and non-spawned oocytes undergo reabsorption. Among the Volutidae, Adelomelon brasiliana is the only species known to lay free egg capsules. The distribution of egg capsules is aggregated due to bottom currents. Egg capsules are often stranded on the beach after strong storms; there they die or suffer predation by shore birds. Gonad development of Zidona dufresnei (Donovan, 1823) (Caenogastropoda: Volutidae) was studied over a period of two consecutive years. The reproductive season in this species in the sampled locality off Mar del Plata extended from October to March. Size at first gonadic maturity in females was 12.8 cm shell length and in males 12.0 cm shell length, but size at which 50% of the population was mature was 15.7 cm in females and 15.0 cm in males. The record of stable isotopes ratio 18O deposited in the shell calcium carbonate of Z. dufresnei that reflects seasonal oscillations in water temperature was used to infer size-at-age. Three years of sampling of Odontocymbiola magellanica (Gmelin, 1791) and Adelomelon ancilla (Lightfoot, 1786) by scuba diving in depths of 6−10 m were performed in Golfo Nuevo, Patagonia, in order to study the spawning seasons, the diet and imposex occurrence. Imposex was registered in individuals of Adelomelon beckii (Broderip, 1836) off Mar del Plata (50−60 m depth); thus A. beckii is the deepest-occurring species where imposex was observed in the southwestern Atlantic.