Pyramidellidae
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Odostomiinae Pelseneer, 1928 |
The Pyramidellidae, or the pyram family or pyramid shells, is a large family of parasitic gastropods with a blunt, heterostrophic protoconch, often pointed sideways or wrapped up.
The pyram family comprises more than 6000 species in over a hundred genera (Schander et al. 1999). This family of micromullusks has been little studied and the phylogenetic relationships within the family are not well worked out. It is currently divided into 11 subfamilies; Odostomiinae, Chrysallidinae, Turbonillinae, Cingulininae, Eulimellinae, Pyramidellinae, Cyclostremellinae, Odostomellinae, Sayellinae, Syrnolininae and Tiberiinae.
The length of the slender, elongated (turreted or conical) shells varies between 0,5 mm and 3.5 cm, but most 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 dextrally 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.
They 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). They do not have a [[radula|. Its 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, the mentum ( = thin projection) is visible.
These mollusks are hermaphrodites, laying its eggs in jellylike masses on the shell of its host. Some species have spermatophores (Høisaeter, 1965, Robertson, 1967)
