Clenchiella iriomotensis, 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 : 123-126

Clenchiella iriomotensis n. sp.

Figures 1 , 3 , 4 , 11–14

Clenchiella sp.; Yamashita et al., 2005: 48, 51, 61, fig. 1; Fukuda, 2012: 40, text fig.

Etymology. Named after the type locality, Iriomote Island.

Types and type locality. Holotype: In shallow tide pools on the back marsh with mangrove trees of the Urauchi River Estuary, 1500 m SW from the Urauchi Bridge, Iriomote Island, Taketomi-chô, Yaeyama-gun, Okinawa Prefecture, Japan, 24˚23’53” N, 123˚45’53” E, 22 Nov. 2004. Coll. H. Fukuda, H. Yamashita, M. Kimura, K. Suzukida, K. Kuroda and C. Mori (AMS, C.462961). Paratypes: Same data (AMS, C.460377, 18 spms; AMS, C.445413. 20+ spms; OKCAB, M17940, 100+ spms).

Material examined. Type material. Iriomote Island, Okinawa; mangrove swamp in Nakara River Estuary, Shirahama, 24˚21’31” N, 123˚45’09” E ( OKCAB, M17940, 9 spms); Maera River Estuary, Komi, 24˚18’47” N, 123˚54’19” E ( OKCAB, M17942, 9 spms); swamp 200 m SW from Ôhara Elementary School, Ôhara, 24˚16’15” N, 123˚52’35” E ( OKCAB, M17943, 3 spms); among green algae in mangrove swamp around Urauchi-bashi Bridge, 24˚24’10” N, 123˚46’34” E ( OKCAB, M17939, 14 spms; M17944, 31 spms).

Distribution. Known only from Iriomote Island, SW Okinawa.

Description. Shell. Shell small (up to 2.3 mm in maximum diameter; Table 3), spire flat ( Figs 1 J–L and 3H–L). Protoconch not elevated above spire, about 1.4 whorls, surface slightly worn in available specimens but protoconch I with traces of few widely spaced spiral threads, termination indistinct; protoconch II about 0.75 whorl, apparently smooth, terminated by very weak varix. Teleoconch of about 2 whorls, rounded except for weak angulations from two carinae, one mid-dorsal, one mid-basal; whole surface sculptured with distinct spiral sculpture: on inner dorsal part of shell spirals weak to subobsolete, with linear interspaces; on outer side of dorsal carina spiral lirae have interspaces up to twice their width while on periphery lirae weaker to subobsolete, with narrow interspaces; at end of penultimate whorl about 5–6 lirae on outer side of dorsal carina, spirals on inner side subobsolete; irregularly spaced commarginal growth lines cross spirals. Periphery evenly convex. Outer base with spiral sculpture as on outer dorsal surface. Base evenly convex except for mid-basal carina; umbilicus wide (more than half width of base), spiral sculpture weaker than on base, becoming subobsolete within. Sutures moderately impressed. Aperture near circular, with simple, slightly thickened peristome, external varix weakly to well developed, narrow, slightly behind edge of aperture. Periostracum variable in colour between individuals; some are reddish brown, some beige, some bluish grey, with few individuals with combinations of these colours. Shell white.

Operculum. Horny, near circular, of up to 8 slowly increasing whorls ( Fig. 4 C, D). Interior with narrow, raised edge to muscle attachment area close to slightly thickened, ridge-like columellar edge and very small, hardly raised nipple in middle.

Head-foot. Living animal generally similar to Cl. victoriae . Snout with several narrow longitudinal stripes of black pigment, and black near distal bands on tentacles ( Fig. 11 ). Bright lemon yellow pigment cells scattered along tentacles. Black pigment also found on neck and around eyes, anterior lateral foot and lateral stripe along dorsal sides of foot. Foot expanded laterally anteriorly and anterior edge indented; tapers posteriorly to point. Opercular lobe thin. Sole translucent white except for scattered white mucous gland cells. Long, stationary cilia on distal ends of tentacles. Cilial tufts on left tentacle not noted.

Ctenidium . About 30 filaments.

Radula . Typical of family. Cusp formulae 4+1+4, 3–4+1+4-5, 20–22, 23–25, median cusps of central and lateral teeth long (twice as long as adjacent cusps or longer), slender, pointed; other cusps on all teeth slender, pointed ( Fig. 12 ).

Gut. Anterior oesophagus with two weak folds; rectum with one tight loop.

Penis. Moderately long ( Fig. 13 A–C), wide distally and narrow proximally; on distal portion two large, distinct, round lobes, one on right edge, another on middle part. Narrow papilla arising from left edge of penis, with pointed tip. Penial duct very slightly undulating to almost straight.

Oviduct. Albumen gland slightly shorter than capsule gland ( Fig. 13 D, E). Coiled oviduct wide, with single very large coil. Seminal receptacles short, about equal in size. Ventral channel rather long, narrow, straight. Bursa extremely large, elongately-oval, lying on left side of oviduct gland, about 1/3 behind posterior wall of mantle cavity; posterior part as wide as anterior part; bursal duct with C-shaped curve at anterior end on left side of capsule gland. Genital opening simple, on ventral edge of meeting point of ventral channel and bursal duct.

Nervous system. As for Cl. bicingulata .

Remarks. The shell of this species is very similar to that of both Cl. varicosa and Cl. bicingulata . The spiral cords are weaker and fewer in Cl. varicosa , as are the main keels, while Cl. bicingulata has stronger spiral sculpture, especially on the periphery and the aperture is more strongly inclined. The rectum of Cl. iriomotensis has only one loop, a character shared with Cl. varicosa whereas other species in the family have two loops (condition in Cl. victoriae unknown). These two latter species also have a somewhat similar penial morphology, although one of the distal glands is smaller in Cl. varicosa . Clenchiella iriomotensis differs significantly, however, from Cl. varicosa in the female genital system, with the bursa copulatrix having a very different configuration (cf. Figs 10 C, D and 13D, E), although it is rather similar to that of Cl. bicingulata .

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 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 11. Head-foot of Clenchiella iriomotensis (AMS C. 445413). A, head, dorsal view; B, head-foot, lateral view; C, sole. Scale bars: 200 µm. Abbreviations: amg, anterior mucous gland, cc, compound cilia; db, distal pigment band on cephalic tentacle; ol, opercular lobe; gc, gland cells; s, snout.

FIGURE 12. Radula of Clenchiella iriomotensis (AMS C. 445413). A, central, lateral and marginal teeth; B, central teeth; C, lateral teeth; D, marginal teeth.

FIGURE 13. Reproductive anatomy of Clenchiella iriomotensis (AMS C. 460377). A, head and penis, dorsal view; B, penis, dorsal view; C, penis, ventral view; D, female reproductive system shown from anterior (left) to posterior (right); E, female reproductive system shown from posterior (left) to anterior (right). Scale bars: 200 µm. Abbreviations: ag, albumen gland; bc, bursa copulatrix; bd, bursal duct; cb, cut base of penis; cg, capsule gland; co, coiled oviduct; pd, penial duct; pl, penial lobe; pp, penial papilla; 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).