Studies on marine comercial snails in Argentina (Caenogastropoda: Volutidae)

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

Museo del Templo Mayo-Palacio de la Autonomía, Ciudad de México.

Congreso; VII Congreso Internacional de Malacología Médica Aplicada; 2004

Distribution ofegg capsules is aggregated due to bottom currents. Egg capsules are often stranded on the beach after strong stoms, where they die or are predated on by beach birds. An Adelomelon ancilla (Lightfoot, 1786) population was sampled by scuba diving in Golfa Nuevo, Patagonia (6-8 m depth). Egg capsules were found from August to March; they were attached to stones, empty bivalve shells and the egg cases of elasmobranchs. Intracapsular supplementary food for lhe embryos was recorded in the form of a viscous milky substance. A clutch of 2-8 embryos develops and hatching takes place at the crawling stage. Adelomelon beckii (Broderip, 1836) is the species with the largest shell in the S.W. Atlantic (up to 50 cm length). The species spawns a single egg capsule attached to a hard substrate, where 7 to 9 embryos develop to the crawling stage. This is the hatching stage. In the sampled region off Mar del Plata (50-60 m depth) individuals collected measured 20 - 30 cm shell length. Cases of imposex were recorded, indicating that A. beckii is the deepest-living species in which masculinization occurs in the S.W. Atlantic. Gonad development of Zidona duresnei (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 the size at which 50% of the population was niature was 15.7 cm in females and 15.0 cm in males. The record of stable isotope ratio (18O/16O) deposited in the carbonate of Z. dufrasnei shells reflects seasonal oscillations in water temperature and was used to infer size-at- age. Two years sampling of Odontocymbiola magellanica (Gmelin, 1791) by scuba diving in depths of 6-10 m were performed in Golfo Nuevo, Patagonia, in order to study the spawning seasons, diet and the occurrence of imposex. O. magellanica females spawn white, spherical, calcareous egg capsules attached to small rocks and hard flat surfaces from July to November. Observations show that O. magellanica is a specialized predator on several bivalves, notably Veneridae. O. magellanica showed between 85.7% and 100% imposex near harbors with low water currents (Puerto Madryn), and a Relative Penis Size Index (RPSI) between 0.77 and 3.84. This occurrence of imposex confirms the presence of TBT in the area.egg capsules is aggregated due to bottom currents. Egg capsules are often stranded on the beach after strong stoms, where they die or are predated on by beach birds. An Adelomelon ancilla (Lightfoot, 1786) population was sampled by scuba diving in Golfa Nuevo, Patagonia (6-8 m depth). Egg capsules were found from August to March; they were attached to stones, empty bivalve shells and the egg cases of elasmobranchs. Intracapsular supplementary food for lhe embryos was recorded in the form of a viscous milky substance. A clutch of 2-8 embryos develops and hatching takes place at the crawling stage. Adelomelon beckii (Broderip, 1836) is the species with the largest shell in the S.W. Atlantic (up to 50 cm length). The species spawns a single egg capsule attached to a hard substrate, where 7 to 9 embryos develop to the crawling stage. This is the hatching stage. In the sampled region off Mar del Plata (50-60 m depth) individuals collected measured 20 - 30 cm shell length. Cases of imposex were recorded, indicating that A. beckii is the deepest-living species in which masculinization occurs in the S.W. Atlantic. Gonad development of Zidona duresnei (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 the size at which 50% of the population was niature was 15.7 cm in females and 15.0 cm in males. The record of stable isotope ratio (18O/16O) deposited in the carbonate of Z. dufrasnei shells reflects seasonal oscillations in water temperature and was used to infer size-at- age. Two years sampling of Odontocymbiola magellanica (Gmelin, 1791) by scuba diving in depths of 6-10 m were performed in Golfo Nuevo, Patagonia, in order to study the spawning seasons, diet and the occurrence of imposex. O. magellanica females spawn white, spherical, calcareous egg capsules attached to small rocks and hard flat surfaces from July to November. Observations show that O. magellanica is a specialized predator on several bivalves, notably Veneridae. O. magellanica showed between 85.7% and 100% imposex near harbors with low water currents (Puerto Madryn), and a Relative Penis Size Index (RPSI) between 0.77 and 3.84. This occurrence of imposex confirms the presence of TBT in the area.