Durckheimia lochi, Ahyong, Shane T. & Brown, Diane E., 2003

Ahyong, Shane T. & Brown, Diane E., 2003, Description of Durckheimia lochi n. sp., with an annotated checklist of Australian Pinnotheridae (Crustacea: Decapoda: Brachyura), Zootaxa 254, pp. 1-20 : 5-8

Durckheimia lochi n.sp.

Figs. 1–2

Type material. HOLOTYPE: AM P24478, ovigerous female (cw 9.8, cl 7.7 mm), Moore Reef near Cairns, Queensland, 16°54’S, 146°12’E, 9.1 m, host Ctenoides ales (Finlay, 1927) (AM C103731), in crevice on bommie, I. Loch, 18 Jan 1976. PARATYPE: AM P24101, 1 ovigerous female, (cw 7.1 mm, cl 6.1 mm), Broadhurst Reef, near Townsville, Queensland, 18°58’S, 147°42’E, 11 m, host Lima lima vulgaris (Link, 1807) (AM C 102954), under coral on bommie, I. Loch, 14 Sep 1975.

Diagnosis of female (males unknown). Carapace subtrapezoid, broader than long, all margins, upturned; anterior margin transverse, strongly produced, with deep, narrow, slitlike median notch. Dorsal surface with prominent, cristate longitudinal median carina, interrupted at midlength by deep notch. Third maxilliped with ischiomerus about 2/3 as wide as long, proximal ¾ of inner margin straight; palp 3­segmented; tip of dactylus slightly falling short of propodal apex; exopod with 2­segmented flagellum.

Description of female (males unknown). Carapace: subtrapezoid, broader than long, with thin, continuous, upturned rim around all margins; anterior margin strongly produced and upturned, transverse with deep, narrow, slit­like median notch. Dorsal, lateral and frontal surfaces non­setose, glabrous except for several shallow, irregular depressions or pits on dorsum; with prominent, cristate longitudinal median carina extending from base of frontal median notch posteriorly to the up­turned, thickened posterior edge of carapace; median carina interrupted at midlength by deep notch; regions undefined. Anterior surface of carapace above and lateral to orbits glabrous and relatively uniform, without deep excavation.

Antennules and antennae: Antennular sinus larger than orbit; antennules folded obliquely. Antennae of 5 segments, basal 2­segments fused to epistome.

Eyes: small, pigmented, filling orbit, not visible in dorsal view.

Third maxilliped: Ischium and merus indistinguishably fused. Ischiomerus about 2/3 as wide as long; proximal ¾ of inner margin straight; outer margin strongly convex. Palp 3­segmented, inserted subdistally on outer margin of ischiomerus. Carpus shorter than propodus. Propodus spatulate, longer than wide tapering to blunt apex; margin setose. Dactylus digitiform, distally setose, inserted slightly proximal to propodal midlength, apex slightly falling short of propodal apex; exopod with 2­segmented flagellum, distal segment setose.

Pereopod 1 (cheliped): Chelipeds symmetrical. Dactylus and pollex relatively straight, crossing distally, slightly shorter than propodal palm; occlusal margins crenulate, dactylus with blunt proximal projection; pollex with fringe of short setae on inner ventral margin.

Pereopods 2–5 (walking legs): Pereopods 2–5 similar and symmetrical from left to right; relative lengths in decreasing order 3>4>2>5. Dactyli falcate, laterally compressed, sparsely setose (densest on pereopod 2), apices spiniform; about half length of propodus. Propodus and carpus unarmed, glabrous, former about 1.5 times length of latter. Merus longer and deeper than other segments, with cristate dorsal margin, glabrous.

Abdomen: broader than long, covering thorax, reaching base of third maxilliped; comprising 7 free segments (including telson), widest at segment 5.

Hosts. Both specimens were collected from the mantle cavities of species of the bivalve mollusc family Limidae . The holotype was found inside Ctenoides ales (Finlay, 1927) ( Fig. 2 ) and the paratype from Lima lima vulgaris (Link, 1807) .

Colour in life. Uniform tan­orange. Eggs bright red­orange.

Etymology. Named in honour of Ian Loch, Australian Museum, who collected and photographed the type material, and has contributed much to the invertebrate collections of the Australian Museum.

Remarks. Durckheimia lochi , new species, resembles D. yokotai and D. caeca in having a cristate median carina on the carapace that extends from the base of the frontal notch, to the posterior margin of the carapace. The long, cristate median carina in the aforementioned species contrasts with that of D. carinipes which has a broad, blunt median carina that is distinct only on the posterior two­thirds of the carapace, and D. besutensis which lacks the median carina altogether. Durckheimia lochi resembles D. caeca in having a subtrapezoid carapace but differs most significantly in having an interrupted instead of entire median carina on the carapace. Durckheimia lochi resembles D. yokotai in having an interrupted median carina on the carapace but differs in having a transverse instead of rounded frontal carapace margin, and a narrow instead of broad, U­shaped median frontal notch.

Durckheimia lochi differs from congeners in characters of the third maxilliped: 1) the ischiomerus is comparatively broader, with a width of about 2/3 the length instead of about half the length; 2) the inner margin of the ischiomerus is straight instead of concave (as in D. caeca and D. yokotai ) or convex (as in D. carinipes and D. besutensis ); 3) the apex of the dactylus falls slightly short of the apex of the propodus whereas in other species, the apex of the dactylus reaches or slightly exceeds the apex of the propodus (except in D. besutensis which lacks a dactylus). All species of Durckheimia are presently known from very few specimens.

To date, D. besutensis , D. caeca , and D. carinipes are known with certainty only from their respective type localities, namely Peninsular Malaysia, Palau, and the Red Sea. It should be noted that listings of D. caeca from the Philippines are based on an error by Tesch (1918) that was perpetuated by subsequent authors (e.g. Balss 1922, Sakai 1955, 1976, Schmitt et al. 1973). Balss’(1922) record of D. caeca from Japan is probably based on D. yokotai . Durckheimia yokotai is presently known from three Japanese localities (coast of Miyazaki, Kii Peninsula, Amami Group) and D. lochi is known from two localities on the Great Barrier Reef, Australia (Moore Reef, Broadhurst Reef).

Distribution. Known only from the Great Barrier Reef, northern Queensland, at depths of 9.1–11 m from limid molluscs.

Figures

FIGURE 1. Durckheimia lochi n. sp., female holotype, AM P 24478. A, dorsal view; B, anterior region; C, carapace, right oblique lateral; D, third maxilliped, right; E, chela, right outer; F, chela, right inner; G – J, pereopods 2 – 5, right; K, abdomen. Scale A, C, K = 5 mm. B, D – J = 2.5 mm.

FIGURE 2. Durckheimia lochi n. sp., female holotype, AM P 24478, in bivalve mollusc host, Ctenoides ales (Finlay, 1927) (AM C 103731). Photo: I. Loch.