Morphogenesis of planktotrophic veligers of naticidean gastropods
Date
1996
Authors
Pedersen, Roberta Vicki Kostiw
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Abstract
Phytoplanktotrophic larval development of the carnivorous marine snails Polinices lewisii and a related but unidentified genus of Natica was observed and described. Both genera are in the family Naticidae of the prosobranch gastropods. The veliger larvae were provided with phytoplankton and lived under laboratory conditions for over 100 days, during which they developed a protoconch II and 4-lobed velum. Only the veligers of Natica sp. settled and metamorphosed.
Specimens at different stages of development were prepared for histological examination to complement observations on live larvae. Characteristics of the growing shell were observed using scanning electron microscopy. Histological serial sections from three developmental stages assisted description of the changes of the mantle cavity and associated organs, muscular, digestive, circulatory, excretory, nervous and sensory systems. Study of the ontogeny of these larvae revealed that extensive development must occur before settlement and metamorphosis. Many structures are previously undescribed for pre-metamorphic naticids such as preliminary development of boring organ, proboscis and esophageal gland in the foregut of the digestive system. These descriptions may assist with identification of P. lewisii in plankton samples and provide further morphological
information to aid in understanding how the rudiments of the benthic structures develop without encumbering larval swimming and feeding.