Carychium tridentatum ( Risso, 1826 )

Weigand Marie-Carolin Götze Adrienne Jochum, Alexander M., 2012, Outdated but established?! Conchologically driven species delineations in microgastropods (Carychiidae, Carychium), Organisms Diversity & Evolution (New York, N. Y.) 12 (4), pp. 377-386 : 381

Morphospecies Carychium tridentatum ( Risso, 1826)

The white translucent shell ranges from 1.7–2.1 mm in height and measures 0.7–0.9 mm in width. The shell is cylindrical to spindle shaped, the diameter being narrower in relation to height than in the sympatric species C. minimum . Although some individuals (e.g., FE-SEM material for columellar view, Fig. 2 ) have 4½ whorls; other representatives in our material possess 5¼ whorls. This variation in whorl number has been described by previous authors ( Zimmermann 1925; Watson and Verdcourt 1953; Lozek 1957; Pintér 1967; Kerney et al. 1979; Bank and Gittenberger 1985). The surface sculpture of C. tridentatum consists of finely threaded, closely spaced transverse striae. The whorls are positioned more horizontally (dorsal and ventral views) relative to the central axis of the shell in contrast to those of C. minimum and C. mariae . The increased degree of undulation of the upper parietal lamella is mariae and C. tridentatum . Data retrieved from Müller 1774, Risso

Carychium minimum, Müller 1774 Carychium mariae Paulucci, 1878 Carychium tridentatum ( Risso, 1826)

Ovate-conic; well-rounded, lightly convex, Ovate-conic; “more obese form” ( Paulucci 1878); Proportionately more slender than C. minimum ; slightly flattened whorls and indented well rounded whorls and indented suture; spire cylindrical to spindle-shaped; well-rounded suture; faint, rounded, closely-spaced less slender than C. tridentatum ; conspicuous convex whorls and indented suture; fine, transverse striae; penultimate and ultimate transverse riblets; prominent strong striae easily raised, closely-spaced transverse striae;

whorls more convex; shell transparent differentiate this species from C. minimum ; shell penultimate whorl larger than C. minimum ; when fresh transparent when fresh shell transparent when fresh

Height: 1.6 - 1.9 mm (Ø 1.8 mm); Width: Height: max. 1.5 - 2.0 mm (Ø 1.7 mm); Width: Height: 1.7 - 2.1 mm (Ø 1.95 mm); Width:

0.8 - 1.0 mm; Dimensions: twice as 0.85 - 1.0 mm; Dimensions: less than twice 0.8 - 1.0 mm; Dimensions: more than twice long as broad (Ø H/W ~ 2) as long as broad (Ø H/W <2) as long as broad (Ø H/W> 2)

Number of whorls: 4 ½ - 4 ¾ Number of whorls: 4.0 - 4 ½ Number of whorls: 4 ½ - 5 ¼

Ultimate whorl expands somewhat quicker Initial whorls increasing more quickly in Attenuate growth of whorls; evenly convex;

and is thus more convex above the height than C. tridentatum ultimate and penultimate whorls less convex than aperture as the penultimate whorl C. minimum not extending over the aperture Aperture oblique oval, 2/5 or more of shell Columellar lamella broadly extended, directly Height of aperture smaller than 2/5 the shell height; height; outer lip thick and slightly turned under outer wall of shell; thickened on the aperture oblique elliptic; wellthickened lip flares back towards the base; single central edges; columellar lamella almost as wide as more than C. minimum ; single central denticle outer lip denticle; side profile of lip parietal lamella; Columellar lamella almost adorns outer lip Columellar fold more prominent sinuous Narrow, thin parietal lamella as wide as parietal lamella; parietal lamella in C. tridentatum than C. minimum ; parietal demonstrates simple, s-shaped profile; characterized by adapical tongue-like, non- lamella characterized by irregular, doubly less elaborate than that of C. tridentatum sinuous lateral wedge positioned in an upward twisted ridge-like shelf thickening as it bends direction; edges of lamellae contorted, compa- upward and then abruptly vertically downward rable to C. tridentatum and quite different from C. minimum

Ecology hygrophilic; alluvial plains, fens, Ecology sympatric with C. tridentatum south Ecology petrophilic; shaded moist deciduous marshes and riparian zones of the Alps; wide range in Northern Italy, woodlands

France and northwestern corner of former

Yugoslavia characteristic for this morphospecies. Our FE-SEM ventral and side observations and image data of C. tridentatum reveal neither new dimensions nor considerable differences to all previous descriptions of this species ( Fig. 2 ).

Figures

Fig. 2 FE-SEM results of conchological details of Carychium tridentatum, C. minimum and C. mariae morphospecies. Shells are arranged in the following order (left to right): ventral view, side view, dorsal view, columellar view. Locality information can be retrieved from Table 1