Caecum caverna Moolenbeek & Faber, 1987
Taxonomic Characterization: Adult shell slightly curved, tapering towards the end, fragile, translucent, anterior part near the aperture somewhat more strongly curved. Prior to aperture, shell contracts, then swells again at aperture which is circular and sharp. At high magnification, very fine growth lines visible on shell which is smooth. Septum large and protruding, mucronate, flattened above, lower part convex, length 0.14 mm. Septum can be large and protruding, mucronate, flattened above, lower part convex , length 0.14 mm. Shape of the septum is the most variable feature, which is either pointed, rounded or irregular, but the fingernail-like mucro is always present. Color translucent, colorless to a little horny. Embryonal first stage shell (6 paratypes) consists of nearly one whorl, and is weakly sculptured. Second stage (85 paratypes) is more curved and tapering, but with the same type of septum (Moolenbeek et al., 1987).
Disposition of Specimens: Type specimens were deposited in the Zoological Museum, Amsterdam (ZMA), The Netherlands; holotype ZMA Moll. 3.87.019.
Ecological Classification: Stygobitic or stygophilic
Size: Adult shell 1.8 - 2.8 mm
Number of Species in Genus: Numerous
Species Range: Known only from Roadside and Walsingham Caves, Hamilton Parish, Bermuda (Moolenbeek and Faber, 1987).
Closest Related Species: It is difficult to separate Caecum caverna from C. troglodyta. Full grown specimens of the latter have better defined growth rings and a varix which consists of several axial rings (Moolenbeek et al., 1987).
Habitat: Anchialine limestone caves
Ecology: Marine, in silty bottom sediments at 0-7 m depths. Inhabits anchialine caves, shells found in silty bottom sediments, sometimes at the base of rock slopes.
Life History: A total of 85 of the collected specimens were in the second stage, while 6 were in the embryonal first stage (Moolenbeek et al., 1987).
Evolutionary Origins: Caecum caverna does not appear to be closely allied to any Atlantic species (Moolenbeek et al., 1987).
Conservation Status: Restricted to two caves in Bermuda.
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