Observations on the ontogeny of thecosomatous pteropuds (holoplanktic Gastropoda) in the southern Red Sea and from Bermuda

The early ontogeny of Peraclis reticulata, Limacina inflata, L. trochiformis, Styliola subula, Clio convexa, Cl. cuspidata, Hyalocylis striata, Creseis acicula, Cr. virgula, Cuvierina columnella, Diacria quadridentata, D. trispinosa, Cavolinia uncinata, C. longirostris, and C. inflexa is described. Their larval development is characterized, and strategies of ontogeny of pteropods are viewed in the context of their biology and taxonomic position. The reconstruction of the juvenile shell into the voluminous adult shell in Diacria spp. and Cavolinia spp. is described in detail. The general features of the early ontogeny of Thecosomata does not deviate from those of other marine gastropods in essential ways as has been proposed by some authors, but postmetamorphic retainment of the sinistral coiling of the shell as well as reshaping of the juvenile shell in Diacria spp. and Cavolinia spp. are unique features of the euthecosomatous pteropods.