Shell small to minute, elongately ovate to pupoid, with convex whorls, smooth or spirally sculptured, usually with a thin periostracum. Aperture oval to D-shaped, with peristome partially or completely separated from parietal wall. Columella concave, straight or with convex bulge. Protoconch sculptured with minute, irregular, shallow pits. Operculum oval, flat, somewhat thickened, nucleus eccentric, with 0-5 calcareous pegs on, in some species, oval calcareous smear, situated in or near middle of inner surface. Penis simple, tapering with single penial duct opening terminally. Female genitalia similar to Fluviopupa, but with dense white part of capsule gland placed anterior to more translucent section. Seminal receptacle relatively larger than in Fluviopupa species. Head-foot pigmented to non-pigmented, eyes present in surface-living species, absent in subterranean species. Ctenidium present in most species, absent in one subterranean species. Intestine usually with loop on mantle roof.
Insuladrobia Ponder & Köhler, 2024
Class Gastropoda
Infraclass Caenogastropoda
Order Littorinida
Suborder Rissoidina
Superfamily Truncatelloidea
Family Tateidae
Genus Insuladrobia Ponder & Köhler, 2024
Type species: Hemistomia gemma gemma Ponder, 1982, Lord Howe Island.
Original reference: Ponder, W. F., & Köhler, F. (2024). A review of the relationships of the Tateidae of Lord Howe Island. Molluscan Research, pp. 1–7. https://doi.org/10.1080/13235818.2024.2355680
Type locality: Streams on eastern slopes of Mt Lidgbird, Lord Howe Island.
The species of Insuladrobia live in the permanent streams and seepages on Lord Howe Island at all altitudes, and many populations are confined to disconnected pools during times of low precipitation. They do not seem to favour any particular habitat, with the exception of I. minutissima and I. whiteleggei which are phreatic. Where two species live together they do not appear to segregate, but share the same microhabitat. It is assumed that, like most tateids, the Lord Howe Island species feed on bacteria, microscopic algae, diatoms and, possibly, decaying vegetation. In pools where snails were abundant, leaves were sometimes reduced to the veins, apparently as a result of feeding by the snails.
Lord Howe Island.
Previously Ponder (1982) placed the Lord Howe Island species in Hemistomia Crosse, 1872, a genus now known to be restricted to New Caledonia.
Species of Insuladrobia are separated from other Australian tateid genera by their small, elongately ovate to pupoid shell, simple penis, opercular pegs and two to five basal cusps on the central teeth of the radula.
Molecular studies (Ponder & Köhler, 2024) have shown that species of Insuladrobia are not closely related to the New Caledonian type species but instead are related to Austropyrgus.
All the species of Insuladrobia are clustered into distinct geographical locations on Lord Howe Island.
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Ponder, W. F., & Köhler, F. (2024). A review of the relationships of the Tateidae of Lord Howe Island. Molluscan Research, pp. 1–7. https://doi.org/10.1080/13235818.2024.2355680
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Zielske, S. & Haase, M. (2015). Molecular phylogeny and a modified approach of character-based barcoding refining the taxonomy of New Caledonian freshwater gastropods (Caenogastropoda, Truncatelloidea, Tateidae). Molecular Phylogenetics and Evolution 89: 171-181.
