Ostracolethe penevi Dedov & Vu 2025, sp. nov.

Ostracolethe (?) penevi Dedov & Vu sp. nov. Figs 3 C, 9, 10, 11 Material examined. Vietnam • 1 adult; Lào Cai Province, Sa Pa district, Thac Bac (= Silver waterfall); 22.3627°N, 103.7773°E; 1677 m alt.; 23 Oct. 2023; I. Dedov, N. Simov, R. Bekchiev, M. Langurov leg.; forest around touristic area; IBER-BAS 40618. Differential diagnosis. Ostracolethe (?) penevi Dedov & Vu, sp. nov. differs from O. fruhstorfferi by its lighter coloration and different color pattern; longer and more slender body; slightly raised long visceral hump shifted towards the head (not central on the body); longer epiphallus; the positions of the epiphallus caeca, which are successively, one after the other (from the epiphallus to the penis, long and short), not opposite to each other as in O. fruhstorfferi, the vas deferens (vd) entering epiphallus slightly laterally (not clearly lateral as in O. fruhstorfferi), and presence of net-like structure with eight circles near the female part of reproductive system. Description. The body is gracile (Fig. 3 C). The visceral hump is relatively long, slightly raised, and is displaced towards the front of the body. The preserved body dimensions (N = 1) are: body length 38.3 mm, body width 5.7 mm, visceral hump length 15.5 mm, visceral hump width 5.7 mm, length of free mantle flap 5.4 mm, sole length 36.3 mm, sole width 3.0 mm, width of lateral zones of sole 0.85–1.15 mm, width of central zone of sole 0.85–0.9 mm, length of the genital pore (not well visible) 0.8 mm, width of the genital pore 0.55 mm (not well visible) (Fig. 9 A – D). Body primary color is light-yellowish-ocher. On the neck, three well-defined gray-blackish stripes are visible (one on the top and two laterally). The tentacles are yellowish. On light-yellowish-ocher (slightly ocher-reddish in its posterior part) visceral hump numerous gray-blackish dots are visible, sometimes grouped in short stripes or spots with irregular shape. Posterior body almost uniformly light-yellowish-ocher with very small dots, well visible under magnification. The dorsal edge of the Y-shaped dorsal groove behind the visceral hump is yellowish. The sole in living specimens is pale-yellowish, more intense yellowish in its lateral margins. In preserved animals, the complete sole loses its pigmentation, which is also the case for all other body parts of the specimens (Fig. 3 C). All colorful pigments (besides melanin) are dissolved in ethanol during the preservation. The body cavity is not enlarged into the posterior part of the foot, which is fully muscular. The caudal horn protrudes slightly beyond the contour of the body and is similarly colored. The shell is plate-like, oval-rhomboid (3 × 2 mm), at one end with visible, and with sparse growth lines (Fig. 10 A – C). The rudimentary shell is fully covered by the mantle. Reproductive system (Fig. 11 A). The penis is long, thick-walled, and spindle-shaped but slightly pinched around the middle. The penis retractor muscle is attached apically to the posterior end of the penis. The epiphallus is long, about 2 / 3 of the penis length, with 2 caeca: a longer and smaller (1 / 3 of the longer caeca). The vas deferens is comparatively short and entering epiphallus slightly laterally. The free oviduct is relatively short. The vagina is thick and short. The bursa copulatrix is relatively long, finger-like (not divided into a bursa copulatrix and bursa copulatrix duct), closely adjacent to the spermoviduct duct, and reaching about halfway to the albumen gland. The albumen gland is small and pearly-yellowish. An unusual net-like structure was found close to the female part of the reproductive system (Fig. 11 B, C). The structure is relatively large and resembles a symmetric net-like formation with eight holes and has dimensions of 3.7 × 1.7 mm (compared to the 14.5 mm length of the reproductive system). Its function remains a mystery, but given its position, it could be homologous to the mucus glands in Helicidae. However, there are no clearly visible channel (s) between this structure and the rest of the reproductive system, even under high magnification. The structure appears to be attached to the female reproductive system by a tangle of connective tissue. The atrium is tubular. Distribution. North Vietnam, type locality. Habitat. Ostracolethe (?) penevi Dedov & Vu, sp. nov. inhabits the leaves of high herbaceous and shrubby moisture-loving vegetation (Fig. 7 A). Derivatio nominis. The new species is named after Prof. Dr Lyubomir Penev for his incredible contribution to the reputation of Bulgarian science and his tireless, friendly support over the years.