Lewindromia unidentata ( Rüppell, 1830 )

Mclay, Colin L. & Hosie, Andrew M., 2022, The sponge crabs of Western Australia and the Northwest Shelf with descriptions of new genera and species (Crustacea: Brachyura: Dromiidae), Zootaxa 5129 (3), pp. 301-355 : 342-344

Lewindromia unidentata ( Rüppell, 1830)

( Fig. 28 )

Dromia unidentata Rüppell, 1830: 16 , pl. 4 fig. 2, 2a, pl. 5 fig 9.— Alcock, 1900: 139, 1901: 47, pl. 2, fig 6.— Chilton, 1911: 554.

Dromidia unidentata . — Laurie, 1906: 351.— Rathbun, 1910: 367.— Ihle, 1913: 31.— Barnard, 1950: 323, figs. 61h–I.— Garth, 1973: 315, 316, 329, 331.— Sakai, 1976: 11, pl. 2 fig 2, text figs 2a–b.— Lewinsohn, 1977: 9, fig. 1a–e; 1979: 2; 1984: 107.

Cryptodromiopsis unidentata . — McLay, 1993: 192, fig. 7 a–k, 18a; 2001a: 84.— Davie, 2002: 161.— Takeda & Manuel-Santos, 2006: 83, fig. 1A–C.— Takeda & Webber, 2006: 232.

Cryptodromia unilobata Campbell & Stephenson, 1970: 240 , fig. 2 A–I.

Lewindromia unidentata . — Guinot & Tavares, 2003: 74, fig. 11A–D.— McLay & Ng, 2005: 11.— Castro 2011: 32.— Ng & Boyko, 2017: 199, fig. 1A.

Material examined. WAM C13523, Montebello Island , 20°31’S, 116°00’E, 38 m, FRV Soela, 2-12-1979: male 11.4 × 11.8 mm (ascidian cap coated with algal and coral fragments) ; WAM C50515, female 16.9 × 18.1 mm, specimen accompanied by handwritten label only showing “87-1953” [an old Registration Book listing these numbers, entered by the former Curator Ludwig Glauert, suggests that the crab was possibly collected by Harry Butler, 11-11- 1953, from Swanbourne Beach, Perth]

Diagnosis. Carapace longer than wide, oblong-shaped; evenly convex; branchial groove shallow; short dense tomentum; rostrum short, tridentate, median tooth small not visible dorsally; strong supraorbital and suborbital teeth; concave area immediately behind orbit shelf-like; anterolateral margin beginning at orbital level, without teeth. Cheliped without epipod. Female thoracic sternal sutures 7/8 ending together on central raised ridge between bases of P2, apertures directed anteriorly.

Remarks. Lewindromia unidentata was first recorded from Australia as Cryptodromia unilobata Campbell & Stephenson, 1970 , having been found in Moreton Bay Queensland. Guinot & Tavares (2003) erected the monotypic genus Lewindromia to accommodate Dromia unidentata Rüppell, 1830 , because it has several distinctive features. They compared L. unidentata with several sponge carrying genera, but it is more constructive to compare it with species that have an intimate association with ascidians, such as Ascidiophilus Richters, 1880 because L. unidentata often uses ascidians and soft corals for shelter. The life style of Ascidiophilus caphyraeformis Richters, 1880 is described by Gordon (1950). This species lives almost totally enclosed in an ascidian or other soft-bodied host. Lewindromia unidentata has an elongate body with a smooth surface, long P5 to carry its host and female thoracic sternal grooves ending close together between the P2s as found in A. caphyraeformis . However, in Ascidiophilus caphyraeformis the rostrum is strongly projecting forming a triangular extension, entire and supported beneath by a keel, whereas in L. unidentata it is weakly tridentate, a condition more typical of sponge-carrying dromiid crabs. In A. caphyraeformis the rostrum and superior orbital border are continuous whereas in L. unidentata the border is interrupted by a blunt preorbital tooth. In A. caphyraeformis the orbits are exposed, but in L. unidentata they are protected and have a suborbital tooth. The body shape also differs: in A. caphyraeformis the body is divided into 2 unequal sections by deep branchial grooves whereas in L. unidentata these grooves are much weaker and the carapace is more or less ovoid in shape. In L. unidentata uropods are present as dorsal plates (concealed) whereas they are absent in A. caphyraeformis . Lewindromia unidentata has a very hirsute body, densely covered by long setae, whereas A. caphyraeformis only has a short tomentum. In many respects the morphology of L. unidentata is intermediate between the sponge-carrying habit and more specialized ascidian-carrying habit found in A. caphyraeformis .

Distribution. Red Sea, Indian Ocean, Singapore, Japan, Philippines, Queensland, New Caledonia, Kermadec Islands ( New Zealand), Tonga, Hawaii and Easter Island. The present specimen represents a new record for Western Australia. Depth range of L. unidentata is intertidal to 100 m.

Figures

FIGURE 28. Lewindromia unidentata (Rüppell, 1830), female, 16.9 × 18.1 mm (WAM C50515): A, dorsal view; B, ventral view; C, dorsal view anterolateral margin; D, dorso-frontal view with facial setae highlighted; E, lateral view; F, ventral view orbits and rostrum.