Intracapsular developrnent and hatching in Adelomelon brasiliana (Larnarck, 1819) (Gastropoda, Volutidae) from orthern Patagonia, Argentina.

LUZZATTO, D. C.; PENCHASZADEH, P. E.

Charleston

Congreso; 68th Meeting American Malacological Society; 2002

The snail Adelomelon brasiliana (Lamark. 1819) has an increasing demand on themarket. It is a common inhabitant on sandy shallow bottoms (10 - 20 m). It rangesfrom the state of Río Grande do Su\. Brazil. to Río Negro province. Argentina.Monthly samples were collected by trawling during two years at Mar del Plata.Buenos Aires (-38°S, 57°W ).The spawn consists of free capsules of 72 mi of average volume. contairungbetween I to 27 embryos without nurse eggs. Egg capsules are produced duringthe wholé year except for the coldest months (June-August). This observationtogether with the massive spawn occurred every early spring. marking thebeginning of the reproductive season. and the recorded first hatchlings in earlysummer. allow us to estimate _adevelopment time of 90 days.During the sampling periodo a progressive decrease in the abundance sampled wasobserved. We estimate that during the third summer the abundance of egg capsulesin the field decreased 85%.The intracapsular fluid contains a high protein concentration that varies duringdevelopment. AIso the pH decreases during development time. The capsule wallopen always on a predetennined area which is more hyaline during the wholedevelopment periodo The dissolution of the egg capsule at this predetennined areais apparently an enzymatic process at the end of the development. [P]