Reproductive studies on Volutes of the South West Atlantic (Neogastropoda: Volutidae)

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

Antwerp, Bélgica

Congreso; World Congress of Malacology.; 2007

Reproductive patterns and season of five volutid neogastropods have been studied: Adelomelon beckii, Zidona dufresnei and Adelomelon brasiliana from the subfamily Zidoninae in Mar del Plata; Odontocymbiola magellanica and Adelomelon ancilla from north Patagonia (Subfamilies Odontocymbiolinae and Zidoninae respectively). Volutids spawn large egg capsules containing few eggs. The embryos develop and grow for a perid of up to three months; eggs ranged from 90 to 300 µm in diameter, feed extraviteline food contained in the intracapsular lfuid; no nurse eggs occur and they hatch as crawling juveniles exceeding 1 cm in shell length. The reproductive season of A. brasiliana extended from September to April. This is the only volutid to lay free egg capsules. Gonad development in Z. dufresnei reveals a reproductive season from October to March. Size at which 50% of the population mature was 15.7 cm in females and 15.0 in males. Preliminary studies of A. beckii showed the spawning season from August to January. Egg capsules are attached to hard substrate is semi-spherical, with a diameter of 50 mm and 35 mm high and the number of embryos varies from 7 to 9. O magellanica spawn white, spherical, calcareous egg capsules attached to hard flat surfaces. Major oviposition events occurred from July to December, characterized by females aggregation. Male individuals reach maturity at 80 mm and females mature at 90 mm. Oviposition in A. ancilla occur mainly from June to December. Minimum shell length of a females laying egg capsules was 114 mm. In the patagonic species oviposition was coincident wish increasing of photoperiod from winter to summer solstices and not apparently by increasing of water temperature as observed in the species from Mar del Plata.