Description

 

"True" limpets are found in these two superfamilies. They include several very similar shells, but all are solid conical shells. In the true limpets,  featured here, both nutrient and waste streams enter just under the shell, through two, separate grooves in the mantle. This characteristic is common to many primitive gastropods, all of which comprise the Patellogastropoda and Vetigastropoda clades. Their  volcano-like cousins are the keyhole limpets, which differ in having a slit or top opening for the waste stream (see, for eample, Fissurellidae).

Limpets, generally, do not have eyes and seem to be guided mainly by chemoreception based on mucus deposits. Most are shallow water molluscs, but those in the Lepetidae family are a subtidal species. All true limpets are vegetarians.

The more flattened conical shells of the Patellidae family are ideally shaped to protect them against being crushed by waves that pound against the exposed rocky surfaces they cling to. Their large flat foot acts somewhat like a suction cup to attach them. None are stationary. They move about while grazing on vegetation and detritus, some making prolonged trips away from their home base while the tide is in. Of considerable interest is that on returning at dawn, they move about to reorient their body for a precise fit into the scar they had excavated into the rock surface --even after the rock is picked up and moved or re-oriented. 

Species in the former Acmaeidae family are generally smaller. They tend to seek out tide pools and other quiet locations, and the smallest may attach to fronds of vegetation. The Acmaeidae do not apply suction for attachment; rather, they find imperfections in the surface to use for attachement. Like the Patellidae, they are also mobile.

In the deep water limpets of the Lepetidae family, their radula is especially well designed for boring into rock. Recurved teeth are hardened with iron and silicon oxides at the tips.

Currently, Collisella, Tectura, Notoacmaea and most species formerly of the genus, Acmaea, are reclassified to the genus, Lottia (Carlton, 2007) . In these cases, "Acmaea" and "Notoacmaea" are synonyms for "Tectura". The several current families listed below and in the photo gallery are defined by significant differences in soft tissue anatomy (established by scanning electron micrography), chromosome number, and shell microstrucure (Beechey, 2008; Sasaki, 1998).

Classification

Class: Gastropoda

Clade: Patellogastropoda

Superfamily: Patelloidea
Superfamily: Nacelloidea

 

Families & Major Genera 

Lottiidae (shallow water)

Genus: Acmaea

Genus: Lottia [Collisella, Tectura, Notoacmaea]

Patellidae (shallow water)

Genus: Patella

Nacellidae (shallow water)

Genus: Cellana

Genus: Nacella

Lepetidae (deep water)

Genus: Iothia

Genus: Lepeta

Genus: Neomphalus

Genus: Propilidium

Tectura scutum (Rathke, 1833)
synonym, Acmaea scutum (Rathke, 1833)
Plate Limpet
4.5 cm

Lottia insessa (Hinds, 1842)
synonym, Acmaea insessa (Hinds, 1842)
Seaweed Limpet
1.1 cm-2.0 cm

Patella granatina (Linnaeus, 1758)
Sandpaper Limpet
6.1 cm

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