Colenuda kessneri, 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 : 141-143

Colenuda kessneri n. sp.

Figures 28–33

Clenchiellid n. gen. n. sp.; Criscione & Ponder, 2013: 1077. Clenchiellid sp.; Golding, 2014: 4.

Etymology. Named after Vince Kessner who discovered the two new clenchiellids from the Northern Territory.

Types and type locality. Holotype: E. Bamboo Creek, tributary of Daly River, near junction with main river (some estuarine influence), Northern Territory, Australia. At 0.2 m depth, 13°40'05" S, 130°39'32" E, 25 Jun. 1995. Coll. W.F. Ponder, A.C. Miller, D.L. Beechey and V. Kessner (NTM P.53500). Paratypes: Same data (AMS C.462832, 20+ spms; NTM P.53501; 20 spms). Paratypes, same locality, 9 Jul. 1995. Coll. V. Kessner (AMS C.305893, 20+ spms; NTM P.6529, 20+ spms).

Material examined. Type material.

Distribution. Known only from the type locality but may occur in similar conditions in the upper parts of other river estuaries in the Northern Territory.

Description. Shell. Small (up to 1.9 mm in maximum diameter; Table 3), spire slightly raised. Protoconch about 0.8–2.0 whorls, surface eroded in available specimens: details of protoconch I not available; protoconch II apparently smooth, varix weak. Teleoconch of about 2.0–2.2 convex whorls, dorsal surface sculptured with distinct, spiral threads with slightly wider to equal interspaces, about 3–10 at end of penultimate whorl; spirals subobsolete to obsolete on inner part of teleoconch whorls and on outer part in some specimens; spirals subobsolete to obsolete on last third to half of dorsal surface of last whorl; finer, close-spaced commarginal growth lines intersect spirals. Periphery evenly convex, smooth except for traces of very shallow spiral grooves. Base evenly convex, with some very weak spiral threads with linear interspaces present. Umbilicus rather narrow (slightly less than half width of base), subobsolete spiral sculpture continuous within. Sutures weakly impressed. Aperture markedly prosocline, near circular, simple, otherwise simple, slightly thickened peristome, without external varix. Colour semitranslucent white.

Operculum. Horny, near circular, of 5 slowly increasing whorls ( Fig. 30 A, B). Interior with slight raised edge to muscle attachment area close to thickened, ridge-like columellar edge. No projection or white area in middle part.

Head-foot. Not observed alive, but preserved animals have narrow black band on distal part of each cephalic tentacle, and black pigment on dorso-lateral sides of the snout, and distal portion of penis.

Ctenidium . About 20 filaments.

Radula . Typical of family. Cusp formulae 4–5+1+4–5, 2–3+1+4–5, 19–22, approx. 35, median cusps of central and lateral teeth long (up to about 1.5 length of adjacent cusps), narrow, pointed; other cusps on all teeth slender, pointed ( Fig. 31 A, B).

Gut. Anterior oesophagus with two very strong folds; rectum with two tight loops.

Penis. Long, wide, tapering, forming anticlockwise coil when at rest; with no distinct swellings or glands; with thin black pigment on distal portion. Tip narrow, with short, pointed papilla. Penial duct with loop in base, remainder slightly undulating ( Fig. 32 A, B).

Oviduct. Albumen gland slightly shorter than capsule gland. Coiled oviduct wide, with single, large coil. Seminal receptacles long, ventral (right) much longer than dorsal (left). Ventral channel rather long, narrow, gently curved. Bursa oval, moderate in size, lying on left side of oviduct gland, wholly behind posterior wall of mantle cavity; middle part widest, narrowing anteriorly to open to nearly straight, short bursal duct just behind pallial cavity. Genital opening simple, at anterior end of bursal duct ( Fig. 32 C, D).

Nervous system. Similar to that of Cl. bicingulata .

Remarks. Although this species is currently known only from the type locality it may occur in other tidal tributaries in the same region. It is found in a narrow zone at or near the upper limit of tidal influence and is abundant where it occurs.

Figures

FIGURE 28. Holotypes of Colenuda n. gen. and Coleglabra n. gen. (from left towards right: dorsal, lateral and ventral view respectively). A – C, Colenuda kessneri n. sp. (NTM P. 53500; shell diameter 1.79 mm); D – F, Coleglabra nordaustralis n. sp. (NTM P. 53502; shell diameter 1.82 mm); G – I, Coleglabra sentaniensis (ZMA 1206; shell diameter 1.1 mm).

FIGURE 29. Shell characters of Colenuda kessneri (NTM P. 6529; A – E) and Coleglabra nordaustralis (AMS C. 307276; F – K). Colenuda kessneri: A – C, from left towards right: dorsal, lateral and ventral view respectively; D, protoconch; E, dorsal sculptural detail. Coleglabra nordaustralis: F, dorsal sculptural detail; G, protoconch; H, dorsal view; I, J, lateral view; K, ventral view.

FIGURE 30. External and internal view (left to right) of opercula of: A, B, Colenuda kessneri (NTM P. 6529); C, D, Coleglabra nordaustralis (AMS, C. 307276). Scale bars: 200 µm.

FIGURE 31. Radulae of Colenuda kessneri (NTM P. 6529) and Coleglabra nordaustralis (AMS C. 307276). Colenuda kessneri: A, central, lateral and marginal teeth; B, central and lateral teeth. Coleglabra nordaustralis: C, central, lateral and marginal teeth; D, central and lateral teeth.

FIGURE 32. Reproductive anatomy of Colenuda kessneri (NTM P. 6529; A – D) and Coleglabra nordaustralis (AMS C. 307276; E – H). Colenuda kessneri: A, head with 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). Coleglabra nordaustralis: E, head with penis, dorso-lateral view; F, ovary; G, female reproductive system shown from anterior (left) to posterior (right); H, female reproductive system shown from posterior (left) to anterior (right). Scale bars: 500 µm. Abbreviations: ag, albumen gland; bc, bursa copulatrix; cb, cut base of penis; cg, capsule gland; co, coiled oviduct; lo, lobe; oo, oocyte; pd, penial duct; pp, penial papilla; ppw, position of posterior wall of mantle cavity; sr, seminal receptacle; uo, upper oviduct; v, vestibule.

FIGURE 33. Maximum Likelihood phylogeny of the Clenchiellidae based on the partial COI mitochondrial gene. Bootstrap support of> 80 % is indicated by branch nodes. The identifiers ‘ a, b’ by the branch of Clenchiella varicosa n. sp. indicate that identical sequences from the same locality were obtained.