Metamorphic remodeling of a planktotrophic larva to produce the predatory feeding system of a cone snail (Mollusca, Neogastropoda).

Abstract

I used histological sections and 3D reconstructions to document development through metamorphosis of the foregut and proboscis in the conoidean neogastropod Conus lividus. A goal was to determine how highly derived features of the post-metamorphic feeding system of this gastropod predator develop without interfering with larval structures for microherbivory. A second goal was to compare foregut development in this conoidean with previous observations on foregut development in the buccinoidean neogastropod Nassarius mendicus. These two neogastropods both have a feeding larval stage, but they show major differences in post-metamorphic foregut morphology. Basic events in development of the proboscis and proboscis sheath in C. lividus and N. mendicus were similar. However, the elongate buccal tube of C. lividus forms during metamorphosis as a composite of apical epidermal tissue that grows inward and ventral foregut tissue that extends outward. The larval mouth is not carried through metamorphosis. Comparative observations on foregut development in caenogastropods, which now include data on C. lividus, suggest that the foregut incorporates dorsal and ventral modules having different ontogenetic and functional fates. This developmental modularity may have facilitated evolutionary diversification of the post-metamorphic foregut. Foregut diversification in predatory gastropods may have been further fast-tracked by developmental uncoupling of larval and post-metamorphic mouths.