Eumedonus niger H. Milne Edwards, 1834

Ng, Diana G. B. Chia Peter K. L., 2000, A revision of Eumedonus H. Milne Edwards, 1834 and Gonatonotus White, 1847 (Crustacea: Decapoda: Brachyura: Eumedonidae), two genera of crabs symbiotic with sea urchins, Journal of Natural History 34, pp. 15-56 : 18-24

Eumedonus niger H. Milne Edwards, 1834

(®gures 1±4)

Eumedonus niger H. Milne Edwards, 1834: 350 [type locality`cotes de la Chine’]; H. Milne Edwards, 1837: plate 15: ®gure 7; SereÁne et al., 1958: 147 [in key], 237, ®gure 1A [list only]; SereÁne, 1968: 63 [list only]; Stevcic et al., 1988: 1310 [list only]

Gonatonotus crassimanus Haswell, 1880: 455 , plate 26: ®gure 4 [type locality Port Jackson, New South Wales, Australia]; Haswell, 1882: 39 [Port Jackson, New South Wales, Australia]; SereÁne et al., 1958: 238 [list only]; SereÁne, 1968: 63 [list only]

Eumedonus villosus Rathbun, 1918: 27 , plate 13: ®gure 1 [type locality south-east of Double Island Point, Queensland, Australia]; Flipse, 1930: 80, 90 [list only]; SereÁne et al., 1958: 147 [in key], 237, ®gure 1F [list only]; SereÁne, 1968: 63 [list only]; Takeda and Miyake, 1972: 64, 79, plate 3: ®gure 3 [East China Sea]; Sakai, 1976: 296 [in key], 297 [volume in English], 178, 179 [volume in Japanese] [East China Sea]; Miyake, 1983: 212 [list only]; Wu, 1983: 134 [name in Chinese]

Eumedonus crassimanus: Gri n, 1972: 74 [o Cape Moreton and Richmond River mouth, Queensland, Australia]; Stevcic et al., 1988: 1310 [list only]; Takeda and Marumura, 1997: 15, ®gure 1A, B [Kii Peninsula, Japan]

Material examined. HOLOTYPE: male (10.9Ö 10.5 mm) ( MNHN B-646S) (dried specimen),` China coast’.

Others. Australia: One juvenile female ( QM W18649), Northwest Shelf, Western Australia, Station 01B17BT, 20ss00.2¾S, 117ss00.5 ¾E, 53 m, trawled, marine, sublittoral, coll. CSIRO (Commonwealth Scienti®c and Industrial Research Organisation), R. V.`Soela’, 22 February 1983. One male (12.0Ö 12.0 mm) ( QM W18658), Northwest Shelf, Western Australia, Station 03D05BT, 19ss58.2¾S, 117ss49.4 ¾E, 43 m, trawled, marine, sublittoral, coll. CSIRO, R. V.`Soela’, 26 June 1983. One male (11.0 Ö 11.5 mm), one female ( QM W18637), Northwest Shelf, Western Australia, Station 05B02S, 19ss56.7 ¾S, 117ss53.6 ¾E, 41 m, epibenthic sledge, marine, sublittoral, coll. CSIRO, R. V.`Soela’, 26 October 1983. One male, one female ( QM W18653), Northwest Shelf, Western Australia, Station 04B02BT, 19ss56.6¾S, 117ss54.1 ¾E, 44 m, trawled, marine, sublittoral, coll. CSIRO, R. V.`Soela’, 26 August 1983. One male, one juvenile female ( QM W18645), Northwest Shelf, Western Australia, Station 01B18NT, 20ss01.2 ¾S, 116ss57.4 ¾E, 52 m, trawled, coll. CSIRO, R. V.`Soela’, 22 February 1983. One female ( QM W18641), Northwest Shelf, Western Australia, Station 02B01BT, 19ss58.9 ¾S, 117ss51.3 ¾E, 40 m, trawled, marine, sublittoral, coll. CSIRO, R. V.`Soela’, 22 April 1983. One male ( QM W18647), Northwest Shelf, Western Australia, Station 01B06BT, 19ss04.4¾S, 118ss47.5 ¾E, 83 m, trawled, marine, sublittoral, coll. CSIRO, R. V.`Soela’, 16 February 1983. Three males, one female ( QM W18643), Northwest Shelf, Western Australia, Station 03B02BT, 19ss56.8¾S, 117ss53.5 ¾E, 44 m, trawled, marine, sublittoral, coll. CSIRO, R. V.`Soela’, 25 June 1983. One female ( NTM Cr001262), northeast Dampier Archipelago, Northwest Shelf, Western Australia, 20ss06 ¾S, 117ss32 ¾E, 40 m, coll. Northern Territory Fisheries, 21 October 1982. One male (14.9Ö 14.9 mm) ( WAM 114-93), northwest Carnarvon, Western Australia, Station 192, 24ss04¾S, 112ss52 ¾E, 138 m, trawled, marine, sublittoral, coll. CSIRO, R. V.`Soela’, 8 October 1963. Four males ( WAM 112-93), south-west cloates, Western Australia, 23ss39¾S, 113ss11 ¾E, 134 m, beam trawl, with echinoids, star®sh, molluscs, coll. CSIRO, 7 October 1963. One female ( WAM 111-93), north Long Island, near Onslow, Western Australia, 51 m, Honolulu dredge, sand and sponge substrata, coll. Wilson, R. V.`Davena’, 17 June 1960. One male ( NMV J14283 ), Northwest Shelf, between Port Hedland and Dampier, Western Australia, 19ss59.00 ¾S, 117ss21.00¾E, 48 m, on sponges, trawl, coll. Poore, G.C.B. and Lew Ton, 2 June 1983. One male, one female ( NMV J14282 ), east of Gympie, Queensland, Station K4/69, 26ss03¾S, 153ss45¾E, Kimbla Cruise. One male (holotype of E. crassimanus, AM G 5172), Port Jackson, New South Wales, 33ss51¾S, 151ss16 ¾E. One male (9.3Ö 9.5 mm) (syntype of E. villosus, USNM 53433), 20 miles east of Double Island, Queensland, 55 m, F.I.S.`Endeavour’, 1909±14. One male ( ZMUC), Coral Sea, Station 539, 26ss33¾S, 153ss31 ¾E, 55 m, coll. Galathea Expedition, 5 November 1951. Japan: One male (young) (6.5Ö 6.8 mm) ( NSMT), station T 6, KH-68-02, trawled between 29ss23.2 ¾N 126ss29.2 ¾E to 29ss23.7¾N 126ss29.5 ¾E, 97 m depth, by beam trawl, collected with echinoid Goniocidaris (Petalocidaris) biserialis (DoÈderlein) , East China Sea, coll. 22 May 1968. Philippines: One female ( USNM 50914) (as Gonatonotus crassimanus ), station 5149, Sirun Island, Sulu Archipelago, vicinity of Siasi, coll.`Albatross’ Philippine Expedition 1907±1910, 18 February 1908.

Description. Carapace pentagonal, rostrum long, length 0.7±1.1 times width (mean value 0.9), tip of rostrum slightly deēxed; inner supraorbital teeth absent; regions well de®ned; surfaces of carapace, chelipeds and ambulatory legs covered with numerous granules; dorsal surface of carapace pileiferous to di erent degrees, usually pubescent between granulated areas with longer setae on the protogastric regions and distal part of rostrum. Antero- and posterolateral margins clearly demarcated by distinct angle or sharp tooth; anterolateral margin entire, without teeth or lobes, distinctly shorter than posterolateral margin. Lateral carapace teeth very stout, tip usually directed obliquely backwards; base of tooth stout and thick; posterior part of carapace tooth bending sharply towards metabranchial region. Antennules folding obliquely, ca 45ss from horizontal; antennular fossae oblique. Antenna free, does not ®ll orbital hiatus, reaching into orbit; antennal basal segment rectangular. Eyes well developed, ®lling orbit; cornea distinct, pigmented; infraorbital teeth small but distinct, subhepatic teeth absent. Anterior surface of epistome not very low; posterior margin appears entire because of two fused truncate median lobes. Pterygostomial, subhepatic, suborbital regions granulated. Maxilliped 3 quadrate; ischium rectangular, median oblique sulcus deep; merus squarish, anteroexternal angle of merus distinctly auriculiform; exopod just below antero-external edge of merus. Sutures between male thoracic sternites 1 and 2 indistinct, 2 and 3 distinct, shallow; between 3 and 4 interrupted medially, median part depressed, followed by high ridge; surface of male thoracic sternite 1 smooth, of sternites 2±3 granulated; lateral clefts small. Abdomen seven-segmented, sutures for all segments visible; segment 7 distinctly depressed into the abdominal groove. Chelipeds granulose; dorsal margin of palm usually with distinct lamelliform crests in females; carpus with distinct spine on distal inner angle; inner surface of basis-ischium, median, inner and outer proximal part of merus with a strong tooth, structure sometimes appearing lamelliform; chela short, stout, length two times length of ®ngers, height ca two to three times height of ®ngers; ®ngers sometimes carinate, pollex not bent downwards. Anterior margins of ambulatory merus and carpus distinctly cristate; posterior margins of merus usually with two distinct parallel crests; dactylus of ®rst leg not much longer than those on other legs. G1 long, slender, distal part lined with short spines, tip bent approximately 45ss or 90ss. G2 relatively short, distal segment short.

Remarks. Although E. niger was the ®rst eumedonid described, its identity is very poorly known. The ®gure of the species presented by H. Milne Edwards (1837) in his Atlas was rather schematic and no one had re-examined or re®gured the sole type specimen (from` China Coast’). Neither has the species ever been reported since. After comparing the type specimens of E. niger (®gure 1) with those of E. crassimanus ( Haswell, 1880) and E. villosus Rathbun, 1918 (®gure 2), we ®nd that both are conspeci®c with E. niger and must be regarded as junior synonyms. Although the types of E. villosus appear to have a rather short rostrum, in all other aspects they ®t into the current understanding of E. niger . In fact, Gri n (1972) had re-examined the type of G. crassimanus , and showed convincingly that the species was conspeci®c with Eumedonus villosus . Takeda and Miyake (1972) subsequently reported and ®gured E. villosus from the East China Sea, and their specimens are here re-determined as E. niger on the basis of the ®gure provided by them.

Examination of the holotype of E. niger (a dried male), shows that it is a rather atypical specimen in several aspects. The specimen is dried but is still in good condition, except for its sternum, male abdomen and gonopods which cannot be examined due to damage made by the resin glue used for mounting. Comparisons of the type male with the good series of specimens of E. crassimanus and E. villosus from Australia show that they are identical except that the type specimen di ers in three aspects, viz. the body colour (black in E. niger ), the more pronounced and more squamate granules on the dorsal surface of the carapace, and the distinctly forked tip of the rostrum, with the two lobes diverging obliquely outwards (the two rostral lobes are straight and not diverging obliquely outwards in E. crassimanus and E. villosus ).

The black colour of the type specimen of E. niger is very distinctive (hence H. Milne Edwards’ name `niger ’), but is probably not natural. It was probably stained by a preservative before the specimen was set and dried. The granules on the dorsal surface of the carapace of E. niger appear to be more squamate mainly because the specimen is dried. The recent specimens of E. crassimanus and E. villosus look identical to the type male of E. niger when their carapace surfaces are dried. The two obliquely diverging rostral lobes of the type of E. niger on close scrutiny, are asymmetrical, and appear to be the result of regrowth. The distalmost part of each rostral lobe is distinctly thinner, less deeply stained, and the margins are only very faintly granulated. It would appear that the distalmost parts of the rostrum of the type specimen of E. niger had been broken and had regrown before it was collected. Regenerated structures of this type sometimes di er somewhat from the normal condition.

As such, we regard E. niger H. Milne Edwards, 1834 , as the senior subjective synonym of both E. crassimanus ( Haswell, 1880) and E. villosus Rathbun, 1918 .

Distribution. Eastern and western Australia, Japan and China.