Coliracemata mortoni, 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 : 130-134

Coliracemata mortoni n. sp.

Figures 16–22 , 26

Etymology. Named for Professor Brian Morton as a small recognition of his enormous contributions to marine biological and malacological studies on the Hong Kong marine fauna.

Types and type locality. Holotype: Under wood, front edge of mangrove. Mong Tseng Wai, Southern Deep Bay, Hong Kong. 22˚29’ N, 114˚00’E, 16 Apr. 1983. Coll. W. F. Ponder (AMS C.269811). Paratypes: Same data (AMS C.460381, 5 spms).

Material examined. Type material.

Hong Kong: Same data as type material (AMS C.460380, 20+ spms); Tsim Bei Tsui near Lau Fau Shan, seaward edge in mangroves, 22° 28' N, 113° 59' E, 15 Apr. 1992. Coll. W.F. Ponder (AMS C.463401, 2 spms); Tsim Bei Tsui, Deep Bay, mangroves, 22° 28' N, 113° 59' E, 15 Apr. 1983. Coll. W.F. Ponder (AMS C.463405, 3 spms).

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

Description. Shell. Minute (up to 1.9 mm in maximum diameter; Table 3), spire flat ( Figs 16 A–C and 17A–C). Protoconch depressed to slightly elevated above spire, about 1.7 whorls, surface of protoconch I sculptured with about three well-spaced very fine spiral threads, terminated by weak varix; protoconch II of one whorl, smooth, terminated by weak varix. Teleoconch of about 1.6 convex whorls, sculptured with distinct, minutely wavy spiral lirae in middle of dorsal part of shell, inner third of dorsal whorls lacking distinct spirals, interspaces about twice width of lirae, about 4–5 lirae and a few finer spiral threads on outer side of whorl at end of penultimate whorl; finer, close-spaced commarginal growth lines intersect spirals, resulting in netted appearance where stronger spirals occur. Periphery evenly convex, spiral weak to subobsolete on peripheral area. Base evenly convex, with wavy spiral lirae, umbilicus wide (nearly half width of base), distinct spiral sculpture lacking in umbilicus. Sutures deeply impressed. Aperture near circular, with simple, slightly thickened peristome, external varix absent. Colour yellow-brown to dark brown due to periostracum and deposits; shell white.

Operculum. Horny, near circular, of 4–5 slowly increasing whorls, each sculptured externally with fine, oblique wrinkles ( Fig. 18 A, B). Interior with narrow, raised edge to muscle attachment area close to weakly thickened columellar edge. Small white (calcareous?) sub-spiral projection in middle part, with thickened ridge between projection and outer edge of muscle scar.

Head-foot. Similar to that of Coliracemata clarkae but unpigmented except for dense-white spots on head and a few on basal half of tentacles and foot. Posterior end of foot tapering and rounded posteriorly ( Figs 19 and 20 ).

Ctenidium . About 20 filaments.

Radula . Typical of family. Cusp formulae variable on central and lateral teeth; 2–5+1+2–5, 1–2+1+1–4, 14–17, 12–14, median cusps of central and lateral teeth long (about twice as long [or slightly more] as adjacent cusps), narrow, pointed; other cusps on all teeth slender, pointed ( Fig. 21 A, B).

Gut. Anterior oesophagus with two very strong folds; rectum with two tight loops ( Fig. 19 C, D).

Penis. Short, wide distally and proximally ( Figs 20 and 22 ). Five to six distinct clusters of many small, apocrine glands on dorsal edge of middle portion; proximal clusters large, distal ones close to tip small. Tip narrow to wide, blunt, with no distinct papilla. Penial duct slightly undulating.

Oviduct. Albumen gland slightly shorter than capsule gland ( Fig. 22 D, E). Coiled oviduct narrow, with single S-shaped coil with indentations. Seminal receptacles short, about equal in size. Ventral channel gently curved. Bursa small, slender, lying on left side of oviduct gland, about 1/5 behind posterior wall of mantle cavity; posterior part slightly wider than anterior; extremely short bursal duct on left side of capsule gland. Genital opening simple, on anterior end of bursal duct.

Nervous system. Similar to that of Coliracemata clarkae .

Remarks. This species has a similar umbilicus and probably a lower spire than Coliracemata ? microscopica (see below) and is also similar to Co. katurana in shell characters but is much larger. Co. mortoni differs from Co. clarkae in being larger, having more prominent spiral sculpture and a lower spire. The only other similar species found in the same general vicinity is Cl. minutissima , which differs most obviously in having a strong apertural varix. Anatomically it differs from the two congeneric species described herein in details of penial, and female genital tract morphology.

This species may possibly have been combined as part of Tong’s (1986) ‘ Clenchiella sp.’ although she figured and described Clenchiella varicosa n. sp. (see above).

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 19. Head-foot and gut characters of Coliracemata mortoni (AMS C. 460381). A, head, dorsal view; B, posterior end of foot, dorsal view; C, external view of intestine and rectum; D, stomach. Scale bars: 200 µm. Abbreviations: ac, anterior chamber; ct, cephalic tentacle; fp, faecal pellet; int, intestine; o, oesophagus; pc, posterior chamber; r, rectum; ss, style sac.

FIGURE 20. Cephalic and penial characters of Coliracemata mortoni. Mong Tseng Wai, Hong Kong (AMS C. 463401). A – C, cephalic tentacle showing distinct compound cilia on distal tip; D, apocrine glands situated on penis; E, F, penis with clusters of apocrine glands.

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 22. Reproductive anatomy of Coliracemata mortoni (AMS C. 460381). A, male head and penis; B, penis, ventral view; C, penis showing separate groups of apocrine glands; 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; cag, clusters of apocrine glands; cb, cut base of penis; cg, capsule gland; co, coiled oviduct; ct, cephalic tentacle; fa, female aperture; gg, groups of apocrine glands; gm, glandular mass; pd, penial duct; 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.