Clenchiella varicosa, Ponder, Winston F., Fukuda, Hiroshi & Hallan, Anders, 2014

Ponder, Winston F., Fukuda, Hiroshi & Hallan, Anders, 2014, A review of the family Clenchiellidae (Mollusca: Caenogastropoda: Truncatelloidea), Zootaxa 3872 (2), pp. 101-153 : 121-123

Clenchiella varicosa n. sp.

Figures 1 , 3 , 4 , 8 , 10 , 14

Clenchiella sp.; Tong, 1986: 443: 443 (in part?), fig. 2F.

? Clenchiella cf. microscopica ; Ueng & Wang, 2006: 31 –36, figs 1–3 [not of Nevill, 1887].

Etymology. Varicose: strictly meaning a dilated vein (Latin, but here based on varix, a commonly used term for a thickening on the shell, typically behind the aperture).

Types and type locality. Holotype: E Mong Tseng Wai, Hong Kong, in mud and leaves etc. in mangroves, 22°30’ S, 114°00’ E, 16 Apr. 1983. Coll: W.F. Ponder (AMS C.462960). Paratypes: Same data (AMS C.460738, 6 spms).

Material examined. Type material.

Specimens from Taiwan, Tainan City, Wildlife Reserve, 23° N, 120°06’E, 1 Oct. 2006. Coll: Y. Ueng (AMS, C.462993, 6 spms).

Distribution. Known only from Hong Kong and Taiwan, but is presumably more widespread in China.

Description. Shell. Small (up to 2 mm in maximum diameter; Table 3), spire mostly flat with apex slightly raised ( Fig. 1 G–I). Protoconch slightly elevated above spire, damaged in available specimens but protoconch I with 4 widely spaced spiral threads, protoconch II smooth. Teleoconch of about 2 whorls, rounded, moderate to rather weak mid-dorsal spiral cord, causing weak subangulation especially in subadults (in some adults not sufficiently strong to cause angulation), with 2–5 slightly weaker spirals on outer side of main spiral; on inner dorsal part of shell spirals very weak to subobsolete or absent; on outer side of dorsal carina spiral lirae have approximately linear interspaces while on periphery lirae with narrow interspaces. Periphery evenly convex. Outer base with 1–2 mid-ventral spiral cords, not sufficiently strong to cause subangulation; several weaker cords on outer and inner side of mid-ventral spiral(s). Base evenly convex; umbilicus wide (more than half width of base), spiral sculpture subobsolete within inner part of umbilicus. Sutures moderately impressed. Aperture near circular, with simple, slightly thickened peristome, external varix weakly to moderately developed, narrow, slightly behind edge of aperture. Colour yellowish (periostracum), shell white.

Operculum and radula . Not examined.

Ctenidium . About 30 filaments.

Gut. Anterior oesophagus with two weak folds, rectum with two tight loops.

Penis. Similar to Cl. bicingulata , but two lobes on distal portion, one round lobe on right edge, more proximal lobe horizontally elongated; on left edge only one small swelling very close to narrow, pointed tip ( Figs 8 B and 10A, B). Penial duct slightly undulating.

Oviduct. Albumen gland slightly shorter than capsule gland ( Fig. 10 C, D). Coiled oviduct narrow, with single, very large coil. Seminal receptacles short, dorsal (left) longer than ventral (right). Ventral channel short, narrow, straight. Bursa small, lying on left side of oviduct gland, about 4/5 behind posterior wall of mantle cavity; posterior part wide, narrows anteriorly to nearly straight, short bursal duct on left side of capsule gland. Genital opening simple, on anterior end of bursal duct.

Nervous system. Pleural-supraoesophageal connective short. Suboesophageal ganglion shorter and narrower than left pleural ganglion.

Remarks. This species is similar to Cl. bicingulata but has a smaller shell, weaker dorsal and ventral ridges and a weaker varix (shells of both species can be compared in Figures 1 and 3 ) The penial morphology also differs in the arrangement of the glands (see description above), notably in having only two distinct glandular lobes distally instead of three ( Figure 8 ). Unfortunately, the condition of available shell material from Hong Kong was rather poor due to corrosion in the preservative, so SEM figures are not provided.

Shells of the species recorded as Clenchiella cf. microscopica from Shihchu Wildlife Reserve, Tainan City, Southwest Taiwan ( Ueng & Wang 2006) are very similar to this species and we treat them as conspecific. These authors provided photographs of the living animal and SEM figures of the shell and inner side of the operculum. We obtained specimens from the same locality from Dr Y.-T. Ueng, and from our examination of the shells ( Fig. 3 D–F), we regard them as this species pending a more detailed study.

Figures

FIGURE 1. Holotypes of species of Clenchiella with distinct keels (from left towards right: dorsal, lateral and ventral view respectively). A – C, Clenchiella victoriae (USNM 488534; shell diameter 2.1 mm); D – F, Clenchiella bicingulata n. sp. (AMS C. 462959; shell diameter 1.97 mm); G – I, Clenchiella varicosa n. sp. (AMS C. 460738; shell diameter 1.96 mm); J – L, Clenchiella iriomotensis n. sp. (AMS C. 445413; shell diameter 1.94 mm).

FIGURE 3. Shell details of keeled Clenchiella spp. A – C, dorsal, lateral and ventral view of Clenchiella bicingulata (AMS C. 460375); D – F, dorsal, lateral and ventral view of Clenchiella varicosa (AMS C. 462993; specimens from Taiwan); G, protoconch, Clenchiella varicosa (Taiwan); H-L, Clenchiella iriomotensis (AMS C. 445413); H, I, protoconch, J – L, dorsal, lateral and ventral views of shell; J, L, juveniles, K, adult.

FIGURE 4. External and internal view (left to right) of opercula. A, B, Clenchiella bicingulata (AMS C. 460375); C, D, Clenchiella iriomotensis (AMS C. 445413); E, F, Clenchiella minutissima (AMS C. 452018). Scale bars: 200 µm.

FIGURE 8. Penes of A, Clenchiella bicingulata (AMS C. 460375) and B, Clenchiella varicosa (AMS C. 462993). Scale bars: 100 µm.

FIGURE 10. Reproductive anatomy of Clenchiella varicosa (AMS C. 460738). A, male head and penis; B, penis; C, female reproductive system shown from anterior (left) to posterior (right); D, female reproductive system shown from posterior (left) to anterior (right). Scale bars: 200 µm. Abbreviations: ag, albumen gland; bc, bursa copulatrix; cb, cut base of penis; cg, capsule gland; co, coiled oviduct; ct, cephalic tentacle; fa, female aperture; pd, penial duct; pl, penial lobe; ppw, position of posterior wall of mantle cavity; sr, seminal receptacle.

FIGURE 14. Type localities of Clenchiella victoriae, Cl. bicingulata, Cl. varicosa, Cl. iriomotensis, and all recorded localities of Cl. minutissima (type locality Vietnam).