A new species of Novastoa Finlay, 1926 (Mollusca: Gastropoda: Vermetidae) from coral reefs of the Pacific Ocean

Abstract

Abstract.A new species of vermetid gastropod belonging to the genus Novastoa Finlay, 1926, N. rapaitiensis sp. nov., is described from French Polynesia and the Great Barrier Reef, based on morpho-anatomical and molecular data, increasing the recognized extant diversity of this genus from five to six species. The new species is characterized by the largest operculum in the genus to date, with a conspicuous spindle-shaped mammilla that readily distinguishes this species from its congeners. Based on available data, members of the studied populations of N. rapaitiensis sp. nov. are interpreted as a single species, although slight morphological and color differences exist between localities separated by up to 7000 km. The larval development of N. rapaitiensis sp. nov. is inferred to be direct, raising new questions about genetic connectivity and dispersal trajectories across a vast geographic range. Additional molecular data may prove helpful in refining our current knowledge on the morphological variability within this species and verifying the degree of cryptic diversity in this genus.

A novel and enigmatic two-holed shell aperture in a new species of suspension-feeding worm-snail (Vermetidae)

“…In the majority of vermetid species, protection of the apertural opening is accomplished by a horny (or, rarely, partly calcified) operculum that partially or wholly plugs the shell opening when the animal's body is withdrawn into the shell tube. In some worm-snail groups (Dendropoma, Novastoa) these opercula can be massive structures deeply anchored into the animal's foot and forming a protecting lid over a strong shell aperture (Golding et al, 2014;Schiaparelli et al, 2017). Taxa that lack a large operculum (those with small opercula such as Vermetus, or entirely without opercula such as Thylacodes) rely on withdrawing into the shell tube and surrendering to grazing predators the often thin-shelled terminal part of the shell (feeding tube) that is directed toward the food-particle bearing current.…”

Replacing mechanical protection with colorful faces–twice: parallel evolution of the non-operculate marine worm-snail genera Thylacodes (Guettard, 1770) and Cayo n. gen. (Gastropoda: Vermetidae)

“…, Menge et al., 1986 ; Osman, 1987 ; Calvo & Templado, 2005 ; Ramírez et al., 2013 ; Shima, Phillips & Osenberg, 2016 ; Brown et al., 2014 ; Shlesinger, Akkaynak & Loya, 2021 ). In intertidal and reef environments with strong predation pressure by grazing and scraping fish, the defense strategy by members of some genera ( Dendropoma , Novastoa ) includes building strong low-lying shells, reducing the profile further by actively entrenching into the substratum by radula action, and closing the aperture with a large operculum that is held shut by the animal’s strong columellar muscle ( Golding et al., 2014 ; Schiaparelli et al., 2017 ; Bieler, 1983–2023, pers. obs.).…”