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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Direct developing predatory gastropods (Nucella spp.) retain vestiges of ancestral novelties in foregut development

Hookham, Brenda 21 August 2014 (has links)
Predatory gastropods (Neogastropoda) feed with a proboscis (elongate snout) and complex foregut. The presence of developmental modules (semi-autonomous components) in foregut development may have facilitated emergence of predatory feeding. In species with indirect development (feeding larval stage) physical and temporal separation of developing foregut modules (dorsal=larval esophagus; ventral=juvenile feeding structures) allows larval feeding and rapid switch to carnivory. However, previous studies on neogastropods with direct development (no feeding larval stage) did not identify foregut developmental modules. Thus, I investigated foregut development in two predatory, direct developing neogastropods: Nucella lamellosa and N. ostrina (Muricoidea), using histological sectioning, 3D reconstructions, TEM, and SEM. In both species, I showed evidence for dissociable dorsal and ventral foregut developmental modules. In N. lamellosa, the two modules were physically separate, although they were not separate in N. ostrina. My results reconcile differences in previous descriptions of foregut development between neogastropods with indirect and direct development. / Graduate

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