Pyramidellidae, common name the pyram family, or pyramid shells, is a voluminous taxonomic family of mostly small and minute parasitic sea snails, marine heterobranch gastropod molluscs or micromolluscs.
The pyram family comprises more than 6,000 species in more than 350 genera . This family of micromollusks has been little studied and the phylogenetic relationships within the family are not well worked out. It is currently divided into 11 subfamilies (Ponder & Lindberg 1997). An alternative interpretation is that the family Pyramidellidae is but one of six families within the superfamily Pyramidelloidea (Schander, van Aartsen & Corgan 1999).
Subfamilies in the family Pyramidellidae
Taxonomy of Ponder & Lindberg (1997)
- Chrysallidinae Saurin, 1958
- Cingulininae Saurin, 1959
- Cyclostremellinae Moore, 1966
- Eulimellinae Saurin, 1958
- Odostomellinae Saurin, 1959
- Odostomiinae Pelseneer, 1928
- Pyramidellinae J.E. Gray, 1840
- Sayellinae Wise, 1996
- Syrnolinae Saurin, 1958
- Tiberiinae Saurin, 1958
- Turbonillinae Bronn, 1849
Taxonomy of Schander, Van Aartsen & Corgan (1999)
Taxonomy of Bouchet & Rocroi (2005)
- Subfamily Pyramidellinae Gray, 1840
- Tribe Pyramidellini Gray, 1840
- Tribe Sayellini Wise, 1996 (formerly subfamily Sayellinae)
- Subfamily Odostomiinae Pelseneer, 1928
- Tribe Odostomiini Pelseneer, 1928
- Tribe Chrysallidini Saurin, 1958 (formerly subfamily Chrysallidinae)
- Tribe Cyclostremellini D.R. Moore, 1966 (formerly subfamily Cyclostremellinae)
- Tribe Odostomellini Saurin, 1959 (formerly subfamily Odostomellinae)
- Subfamily Syrnolinae Saurin, 1958 (formerly subfamily Syrnolinae)
- Tribe Syrnolini Saurin, 1958
- Tribe Tiberiini Saurin, 1958 (formerly subfamily Tiberiinae)
- Subfamily Turbonillinae Bronn, 1849
- Tribe Turbonillini Bronn, 1849
- Tribe Cingulinini Saurin, 1958 (formerly subfamily Cingulininae)
- Tribe Eulimellini Saurin, 1958 (formerly subfamily Eulimellinae)
The following genera are currently difficult to place within existing subtaxa
of the Pyramidellidae.
This family is found worldwide.
The shell of these snails has a blunt, heterostrophic protoconch
, which is often pointed sideways or wrapped up.
The length of the slender, elongated (turreted or conical) shells varies between 0.5 mm and 3.5 cm, but most species in the family have shells which are smaller than 13 mm.
The texture of these shells is smooth or sculptured in various forms such as ribs and spirals. Their color is mostly white, cream or yellowish, sometimes with red or brown lines.
The teleoconch is dextral coiled, but the larval shells are sinistral. This results in a sinistrally coiled protoconch.
The columella has usually one, but sometimes several, spiral folds. The aperture is closed by an operculum.
The Pyramidellidae are ectoparasites
, feeding mainly on other molluscs and on annelid worms
, but some are known to feed on peanut worms and crustaceans
(e.g. Sneli, 1972, Robertson & Mau-Lastovicka, 1979).
They do not have a radula. Instead their long proboscis is used to pierce the skin of its prey and suck up its fluids and soft tissues. The eyes on the grooved tentacles are situated toward the base of the tentacles. Between the head and the foot, a lobed process called the mentum (= thin projection) is visible.
These molluscs are hermaphrodites, laying eggs in jelly-like masses on the shell of its host. Some species have spermatophores (Høisaeter, 1965, Robertson, 1967, Schander, Hori & Lundberg, 1999)
- Bouchet, P. & Rocroi, J.-P. (2005). "Classification and Nomenclator of Gastropod Families". Malacologia 47 (1-2): 1–397.
- Høisæter, T. (1965). "Spermatophores in Chrysallida obtusa (Brown) (Opisthobranchia, Pyramidellidae)". Sarsia 18 63–68.
- Ponder, W.F. & Lindberg, D. R. (1997). "Towards a phylogeny of gastropod molluscs: an analysis using morphological characters". Zoological Journal of the Linnean Society 119 88–265.
- Robertson, R. (1967). "The life history of Odostomia bisuturalis and Odostomia spermatophores (Gastropoda: Pyramidellidae)". American Philosophical Society Yearbook 1967 368–370.
- Robertson, R. (1979). "The ectoparasitism of Boonea and Fargoa (Gastropoda: Pyramidellidae)". Biological Bulletin 157 320–333.
- Schander, C., van Aartsen, J. J., Corgan, J. C. (1999). "Families and genera of the Pyramidelloidea (Mollusca: Gastropoda)". Bollettino Malacologico 34 (9-12): 145–166.
- Schander, C., Hori, S., Lundberg, J. (1999). "Anatomy, Phylogeny and biology of Odostomella and Herviera, with the description of a new species of Odostomella (Mollusca, Heterostropha, Pyramidellidae)". Ophelia 51 (1): 39–76.
- Sneli, J.-A. (1972). "Odostomia turrita found on Hommarus gammarus". Nautilus 86 (1): 23–24.
- Gallery of pyramidellids