Diloma nanum is a species of small sea snail, a marine gastropod mollusc in the family Trochidae, commonly known as top snails. It is an endemic species to New Zealand.
Taxonomy
- Kingdom: Animalia
- Phylum: Mollusca
- Class: Gastropoda
- Subclass: Vetigastropoda
- Order: Trochida
- Superfamily: Trochoidea
- Family: Trochidae
- Genus: Diloma
- Species: Diloma nanum (Hutton, 1873)
The species was originally described by Frederick Wollaston Hutton in 1873 as Trochus nanus. It has since been reclassified within the genus Diloma. Synonyms include Zeminolia nanum and Zeminolia nanus.
Description
Diloma nanum is characterized by its small, conical shell, typically reaching a height of up to 10-12 mm and a width of about the same. The shell is generally robust and solid, often appearing black, dark grey, or purplish-brown, sometimes with faint spiral bands or blotches of lighter color. The surface can be smooth or finely sculptured with growth lines and sometimes subtle spiral striae. The apex (tip) of the shell is often eroded in older specimens. The aperture is iridescent internally, a common feature among trochid snails. The columella (inner lip of the aperture) is typically smooth and lacks a tooth.Distribution and Habitat
Diloma nanum is endemic to New Zealand, where it is found around the coasts of the North Island, South Island, Stewart Island, and the Chatham Islands.This species is common on rocky shores, particularly in the mid to high intertidal zone. It inhabits exposed and semi-exposed areas, often clinging to rocks, within crevices, or under stones. It can tolerate periods of aerial exposure at low tide, surviving by clamping tightly to the substrate to reduce water loss.