| | The families of non-marine molluscs of Britain and Ireland (slugs, snails and mussels) |
Morphology. Limpets, with a conspicuous, protective patelliform shell bearing only a vestigial spire (the latter represented by the backward pointing apex).
The animal with one pair of tentacles only. Eyes at the bases of the tentacles.
The shell vestigially rising-spiral, or . The animal sinistral, with the genital orifice and anus opening on its left side, although the vestigial spire of the shell is slightly twisted to the right. The shell wider than high; 4–8 mm wide (somewhat less than this across, but much more broadly ovate than those of Acroloxus lacustris). The shell very asymmetric about the vertical axis, with the spire much displaced to one side (i.e., taking account of the displaced vestige of the spire). The shell opaque; greyish horn-coloured, with strong radiating striae and fine growth lines; plain.
General biology, ecology. Freshwater aquatic. The mantle cavity obliterated, and a lobe of the mantle functioning as a gill (and gas exchange also occurring via the skin in general). A. fluviatilis lives in quick-flowing, soft or hard water, attached firmly to stones and grazing on algae and mosses. F. wautieri, by contrast, usually attaches to submerged plants in stagnant or slowly moving water.
Hermaphrodite (but individuals acting as either male or female when mating).
Classification. Gastropoda; Pulmonata.
Representation in Britain and Ireland. “Limpets”: Ancylus, Ferrissia.
Illustrations. • Ancylus fluviatilis, with Acroloxus lacustris (Reeve). ANCYLIDAE. 1, Ancylus fluviatilis Müller ("River Limpet"). ACROLOXIDAE. 2, Acroloxus lacustris (L.), "Lake Limpet". From Reeve (1863), with approximate scales added. • Ancylus fluviatilis, with Acroloxidae and Lymnaeidae (Adams). LYMNAEIDAE. 1, Myxas glutinosa (Müller), "Glutinous Snail". 2, Lymnaea involuta Thomson, probably a form of L. peregra. 3b, Lymnaea peregra (Müller), "Common Pond Snail, Wandering Pond Snail". 3a and 3e, Lymnaea ovata (Draparnaud), probably also a form of L. peregra. 4, Lymnaea auricularia (Linn.), "Ear Pond Snail". 5, Lymnaea stagnalis (Linn.), "Great Pond Snail". 6, Lymnaea palustris (Müller), "Marsh Pond Snail". 7, Lymnaea truncatula (Müller), "Dwarf Pond Snail". 8, Lymnaea glabra (Müller), "Mud Pond Snail". ANCYLIDAE. 9, Ancylus fluviatilis Müller, "River Limpet". ACROLOXIDAE. 10, Acroloxus lacustris (Linn.), "Lake Limpet". From Adams (1896).
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The families of non-marine molluscs of Britain and Ireland (slugs, snails and mussels). Version: 5th August 2019. delta-intkey.com’.
