Tbe spawn in the genusAdelomelon (Prosobranchia: Volutidae) from the A tlantic coast of South America

PENCHASZADEH, P. E.; COSTA, P. M. S. ; LASTA, M.; MILOSLAVICH, P.

Santa Bárbara, California

Encuentro; AMU/WSM 1997 Annual Meeting; 1997

The Western Society of Malacologists (WSM) Y American Malacological Union (AMU)

Since the early descriptions of egg capsules of South American volutes in the past ccntury, vcry fcw additions havebeen made, many of them unfortunately proved to be wrong. We describe here thc cgg capxulc 01' thc l.rrgcs: SouthAmerican volute, Adelomelon becki (Broderip, 1836). and redescribe the often confuscd xpawn or 1\. III/('i/l1l (Lightfoot,1786). The spawn of A. becki is a single. conspicuous, large, globose and hemispheric cgg capsulc auuchcd !O pectinidshelIs, measuring 50 mm in basal diarneter and 35 mm in height. The baseis round and has a narrow (3 mm) marginoThenumberofembryos ranges from 7 to 10. The sizeathatchingwas 16.0to 18.6mm in shcll length. The internal volume ofthe egg capsule was 30 to 35 ml. No nurse eggs were observed. All the studied material was al a pre-hatching crawlingstage,The egg capsule of A. ancilla is oval and flat, with a diameterranging from 37 to 45 mm, nevcr covercd by él calcareouslayer. They are generally attached to pectinid shells. The number of eggs per capsule is 5-8, and so is the number ofdeveloping embryos; no nurse eggs are present. The eggs are 150 microns in diamctcr and are surrounded by a verydense liquid, The intemal volume ofthe egg capsule ranged from 2.5 to 4.0 ml. Hatching iakes place as crawlingjuveniles.the shell measuring between 11.7 and 12.7 mm.