Common Keyhole Limpet

Diodora graeca

Diodora graeca is a small, oval-shaped limpet with a flat shell that typically measures about 25 mm in length and 18 mm in width. The shell is shield-like and features a keyhole-shaped aperture located at the top, which allows for the expulsion of water and waste. Its surface is slightly reticulated, displaying concentric cords crossed by radial ridges, with alternating larger ridges. The coloration ranges from creamy white to yellow-white, often with a slight orange tint. This species can be distinguished from similar limpets by its unique shell shape and the presence of the keyhole aperture. Commonly found in the Mediterranean and the North Atlantic, this limpet inhabits rocky substrates in the sublittoral zone, typically at depths ranging from low tide down to about 200 meters. It prefers to cling to rocks or hide beneath stones, making it a common sight on the coasts of Ireland and western Britain. The Common Keyhole Limpet primarily feeds on algae and detritus, utilizing its broad creeping foot to graze on available food sources. Reproduction in Diodora graeca involves broadcast spawning, where individuals release eggs and sperm into the water column. The resulting embryos develop into planktonic larvae before settling down to mature into adults. Encountering this limpet while diving can be intriguing, as divers may spot them clinging to rocks or moving slowly across the substrate. The species is recorded at numerous dive sites, indicating its widespread presence in suitable habitats.