A Veliconcha Unveiled: Observations on the Larva and Radula of Conus spurius, with Implications for the Origin of Molluscivory in Conus

Abstract

Abstract: The veliconcha larva of the predatory gastropod Conus spurius Gmelin, 1791 is described and for the first time illustrated based on material from Sanibel Island, Florida. Hatchling veliconchas were 1470–1570 μm (mean = 1530) long, with first protoconch whorl maximum diameter 670–740 μm (mean = 710), and estimated egg diameter 570 μm. Veliconchas can swim for a few minutes to a few hours before settling. They have well-developed paired velar lobes each 600–700 μm in length, an extensible foot with a distinct metapodium separated from the remainder of the foot by a transverse fold, and operculum. Several early life history traits of C. spurius, particularly hatching as large veliconcha larvae with predominantly lecithotrophic, nearly non-planktonic development, closely resemble those of a well-defined clade of Conus Linnaeus, 1758 species that prey on other gastropods. They contrast with the majority of species in this hyperdiverse genus, which hatch as much smaller planktonic, obligatory planktotrophic veliger larvae. As adults they comprise a vermivorous feeding guild, preying exclusively or nearly so on polychaete annelids. Limited data suggest that C. spurius may share this trait with them but it may also prey on molluscs. Recent molecular phylogenetic trees suggest that the characters “pelagic development” and “non-pelagic development” (or nearly so: <1 day) are distributed independently of phylogeny in the larger clade that includes C. spurius and the molluscivorous species. Similarities in veliconcha morphology and developmental mode, adult radular tooth morphometry, phylogenetic position, and earliest fossil records suggest the speculative hypothesis that the monophyletic clade of extant molluscivorous Conus species may have evolved in the Miocene from a vermivore or mixed vermivorous-molluscivorous ancestor with these attributes, such as C. spurius.