Coliracemata katurana, 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 : 134-137

Coliracemata katurana n. sp.

Figures 16–18 , 21 , 23 , 24 , 26

Hydrobiidae gen. et sp.; Yamashita et al., 2005: 48, 51, 61, fig. 2. ‘Clenchiella’ sp.; Fukuda, 2012: 41, text fig.

Etymology. Named after Katura, the old name of the region around the type locality (Urauchi River Estuary) of this species.

Types and type locality. Holotype: Among green algae on sandy mud bottom around the roots of mangrove trees, the Urauchi River Estuary, just below the Urauchi Bridge, Iriomote Island, Taketomi-chô, Yaeyama-gun, Okinawa Prefecture, Japan. 24˚24’10” N, 123˚46’34” E, 22 Nov. 2004. Coll. H. Fukuda, H. Yamashita, M. Kimura, K. Suzukida, K. Kuroda and C. Mori (AMS C.269815). Paratypes: same data (AMS C.445414, 3 spms; OKCAB M17938, 11 spms).

Material examined. Type material.

Distribution. Known only from the type locality; Iriomote Island, SW Okinawa.

Description. Shell. Minute (up to 1.3 mm in maximum diameter; Table 3), spire flat ( Figs 16 D–F and 17D–F). Protoconch markedly elevated above spire, about 1.5 whorls, surface slightly worn in available specimens but protoconch I appears to be smooth except for median spiral thread and terminated by distinct varix; protoconch II about 0.8 whorl, with about 11 fine spiral threads, varix indistinct. Teleoconch of about 1.5 convex whorls, whole surface sculptured with distinct, minutely wavy spiral lirae with interspaces about twice their width, about 9–10 at end of penultimate whorl; finer, close-spaced commarginal growth lines intersect spirals, resulting in netted appearance. Periphery evenly convex, spiral lirae similar in strength on peripheral area as on dorsal and basal surfaces. Base evenly convex, umbilicus wide (nearly half width of base), spiral sculpture continuous within. Sutures impressed. Aperture near circular, with simple, slightly thickened peristome, external varix indistinct, very narrow. Colour of periostracum uniformly reddish brown in the few specimens observed.

Operculum. Horny, near circular, of 5 slowly increasing whorls. Interior with narrow, raised edge to muscle attachment area close to thickened, ridge-like columellar edge. Small spiral projection in middle part ( Fig. 18 C, D). Small, triangular white (calcareous?) smear around nucleus on inner side.

Head-foot. Cephalic tentacles long, slender, with no pigment; several stationary setae on distal end. Snout moderate in length, cylindrical. White spots found all over head-foot including sole. Eye large, black, situated behind proximal end of cephalic tentacle. Foot long, slender; anterior end slightly expanded laterally and indented on central part with long transverse mucous slit; anterior mucous gland small, consists of opaque white cells, restricted to central part of anterior foot. Sole colourless with many white spots on lateral sides. Posterior end of foot blunt ( Fig. 23 ).

Ctenidium . 16 filaments.

Radula . Typical of family. Cusp formulae 3–4+1+3–4, 3–4+1+4, 18–19, 13–14, median cusps of central and lateral teeth long (about twice as long as adjacent cusps), narrow, pointed; other cusps on all teeth slender, pointed ( Fig. 21 C, D).

Gut. Anterior oesophagus with two weak folds; rectum as in Co. mortoni , with two tight loops.

Penis. Small, moderately long, wide distally and narrow proximally ( Fig. 24 A, B). One large glandular swelling with four to five clusters of apocrine glands on middle dorsal portion. Short, narrow papilla with pointed tip on distal end. Penial duct not observed.

Oviduct. Albumen gland about as long as capsule gland ( Fig. 24 C, D). Coiled oviduct rather wide, with simple, open coil. Seminal receptacles short, about equal in size. Ventral channel rather wide, rather long, nearly straight. Bursa small, triangular, entirely in front of posterior wall of mantle cavity; bursal duct extremely short. Genital opening simple, slightly posterior to anterior end of capsule gland.

Nervous system. Similar to that of Coliracemata clarkae (see below).

Remarks. This species is the smallest known clenchiellid and is most similar to Co. mortoni n. sp. described above from Hong Kong, but differs in its smaller size. In addition to differences in the genital systems, the distinct, wavy spiral lirae with axial threads produce a netted appearance (visible only with SEM) and extend evenly over the whole shell surface.

Figures

FIGURE 16. Holotypes of new species of Coliracemata n. gen. (from left towards right: dorsal, lateral and ventral view respectively). A – C, Coliracemata mortoni n. sp. (AMS C. 269811; shell diameter 1.82 mm); D – F, Coliracemata katurana n. sp. (AMS C. 445414; shell diameter 1.06 mm); G – I, Coliracemata clarkae n. sp. (AMS C. 462962; shell diameter 1.36 mm).

FIGURE 17. Shells of Coliracemata mortoni (AMS C. 460381; A – C) and Coliracemata katurana (AMS C. 445414; D – F) with dorsal, lateral and ventral views given from left towards right.

FIGURE 18. External and internal view (left to right) of opercula. A, B, Coliracemata mortoni (AMS C. 460381); C, D, Coliracemata katurana (AMS C. 445414). Scale bars: 100 µm.

FIGURE 21. Radulae of Coliracemata mortoni (AMS C. 460381) and Coliracemata katurana (AMS C. 445414). Coliracemata mortoni: A, central, lateral and marginal teeth; B, central and lateral teeth. Coliracemata katurana: C, central, lateral and marginal teeth; D, central and lateral teeth.

FIGURE 23. Head-foot of Coliracemata katurana (AMS C. 445414). A, head, dorsal view; B, lateral view of head-foot; C, sole. Scale bars: 200 µm. Abbreviations: amg, anterior mucous gland, cc, compound cilia; ol, opercular lobe; gc, gland cells; s, snout.

FIGURE 24. Reproductive anatomy of Coliracemata katurana (AMS C. 445414). A, penis, dorsal view; B, penis, ventral view; 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; cag, clusters of apocrine glands; cb, cut base of penis; cg, capsule gland; co, coiled oviduct; fa, female aperture; pp, penial papilla; ppw, position of posterior wall of mantle cavity; sr, seminal receptacle.

FIGURE 26. Type localities of all species of Coliracemata n. gen., Colenuda n. gen., and Coleglabra n. gen.