Studies on Volutids in Argentina (Volutidae: Caenogastropoda)

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

Sanibel Island, Florida, U.S.A.

Conferencia; 70th Annual Meeting American Malacological Society; 2004

American Malacological Society

Adelonrelon brasiliana (Lamarck, 18 1 1) 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 pn 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 afier strong storms; there they die or suffer predation by shore birds. Gonad developmerit of Zidona dufresnei (Donovan, 1823) (Caenogastropoda: Volutidae) was studied over a period of two consecutive years. The reproductive season in this species i11 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 sl~elle ngth, 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 180 deposited in the sliell calciuiu carbonate of Z. ditji-esnei that reflects seasonal oscillations in water tenipztalure was used to infer size-at-age. Three years of sampling of Odontocymbiola mgellanica (Gmelin, 1791) and Adelomelon ancilla (Lightfoot, 1786) by scuba diving in depths of 6-10 nl were performed in Golfo Nuevo, Patago~iiai,n older to study the spawning seasons, the diet and imposex occurrence. Imposex was registered in individuals of Adelomelon beckii (Broderip, 1836) off Mar clel Plata (50--40 rn depth); thus A. beckii is the deepest-occurring species where imposex was obsel-ved in the southwestern Atlantic.(Lamarck, 18 1 1) 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 pn 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 afier strong storms; there they die or suffer predation by shore birds. Gonad developmerit of Zidona dufresnei (Donovan, 1823) (Caenogastropoda: Volutidae) was studied over a period of two consecutive years. The reproductive season in this species i11 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 sl~elle ngth, 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 180 deposited in the sliell calciuiu carbonate of Z. ditji-esnei that reflects seasonal oscillations in water tenipztalure was used to infer size-at-age. Three years of sampling of Odontocymbiola mgellanica (Gmelin, 1791) and Adelomelon ancilla (Lightfoot, 1786) by scuba diving in depths of 6-10 nl were performed in Golfo Nuevo, Patago~iiai,n older to study the spawning seasons, the diet and imposex occurrence. Imposex was registered in individuals of Adelomelon beckii (Broderip, 1836) off Mar clel Plata (50--40 rn depth); thus A. beckii is the deepest-occurring species where imposex was obsel-ved in the southwestern Atlantic.