A revision of Eumedonus H. Milne Edwards, 1834 and Gonatonotus White, 1847 (Crustacea: Decapoda: Brachyura: Eumedonidae), two genera of crabs symbiotic with sea urchins Author Ng, Diana G. B. Chia Peter K. L. text Journal of Natural History 2000 34 15 56 journal article 1464-5262 Eumedonus zebra Alcock, 1895 (®gures 13±15) Eumedonus zebra Alcock, 1895: 288 [ type locality`o Ceylon’ = Sri Lanka ]. Alcock and Anderson, 1896 , plate 23: ®gure 5 [o Sri Lanka ]; Flipse, 1930: 80 , 90 [list only]; Gordon, 1934 : ®gure 32b [ Sri Lanka ?]; Sakai, 1938: 348 , 349 [East China sea] (part); Sakai, 1940: 41 [list only] (part); Sakai, 1956: 25 [appendix list] [list only] (part); SereÁne et al. , 1958: 147 [in key], 237, ®gure 1B, C [list only] (part); Sakai, 1965: 102 , plate 46: ®gure 4 [colour plate] [volume in English], 42 [volume in Japanese] [Sagami Bay, Honshu island, Japan ]; Guinot, 1966: 299 [list only]; SereÁne, 1968: 63 [list only]; Sakai, 1976: 296 [volume in English], 178, 179 [volume in Japanese], plate 99: ®gure 3 [colour plate] [Sagami Bay, Honshu island, Japan ]; SereÁne and Ingle, 1980: 103 [list only]; SereÁne and Vadon, 1981: 124 [north of Lubang Island, Philippines ]; Miyake, 1983: 212 [list only]; Wu, 1983: 134 [name in Chinese]; Stevcic et al. , 1988: 1310 [list only] Eumedonus vicinus : Sakai, 1934: 300 , text-®gure 14 [East China Sea]; Sakai, 1936: 18 , 112, ®gure 53 [East China Sea]; Monod, 1938: 110 , ®gure 8 [Gulf of Suez, Red Sea]; SereÁne et al. , 1958: ®gure 1E [®de Monod] (part) [not Eumedonus vicinus Rathbun 1918 ] Material examined . LECTOTYPE : female ( 7.3Ö 8.1 mm ) ( BMNH 1899.1 .20.7, gift from Indian Museum), Andaman Sea, 101 m , no other data. Others . Madagascar : One male ( 13.4Ö 14.1 mm ) ( MNHN ) , ORSTOM number AC46 , 21 ss53¾S, 43ss10¾E, 150±180 m , coll. MUSORSTOM, FAO 26 Expedition , no other data. One male ( 11.8Ö 11.8 mm ) , one female ( MNHN ), ORSTOM number AC47 ±48, Station P4, 15ss21.0 ¾S, 46ss12.5 ¾E, 150 m , coll. MUSORSTOM, Chalutage 52 Expedition , 8 November 1972 . La Reunion : One juvenile female ( MNHN B-20412), Plessis , November 1973 , no other data. Red Sea : One male ( 11.5 Ö 11.9 mm ), one female ( SMF 21985), Bab-el Mandeb , Station Me 5-230 KD1, 43ss15.0¾E, 12ss43.7 ¾N, 228±235 m , coll. F.S. Meteor , 5 March 1987 . One juvenile male ( MNHN ), Suez Canal , Gulf of Suez , Station X , coll. R . Dollfus , 8 December 1928 . One juvenile male ( MNHN ), Suez Canal , Gulf of Suez , Station XVII bis , coll. R . Dollfus , 26 December 1928 . One female ( MNHN ), Suez Canal , Gulf of Suez , Station VI , coll. R . Dollfus , 29 December 1928 . Indonesia : One female ( MNHN ), ORSTOM number AC49 , Makassar Strait , Station CH208 , 00ss14¾S, 117ss52 ¾E, 150 m , coll. MUSORSTOM, no other data . Philippines : One male ( MNHN ), ORSTOM number AC50 , Lubang Island , Station 64, 14ss00.5 ¾N, 120ss16.3 ¾E, 194±195 m , coll. MUSORSTOM, 27 March 1976 . One female ( MNHN ), ORSTOM number AC51 , Station DR 33, 13ss32¾N, 121ss07 ¾E, 130±137 m , coll. MUSORSTOM, 1976. One male ( MNHN ), ORSTOM number AC52 , Lubang Island , Station 26, 14ss00.9¾N, 120ss16.8 ¾E, 189 m , coll. MUSORSTOM, 22 March 1976 . One male ( ZRC 1997.169 ), Lubang Island , Station 35, 13ss59.0 ¾N, 120ss18.5 ¾E, 186±187 m , coll. MUSORSTOM, 23 March 1976 . One female ( MNHN ), ORSTOM FIG. 13. Eumedonus zebra Alcock, 1895 . Lectotype female, 7.3Ö8.1 mm (BMNH 99.1.20.7): A, dorsal view; B, ventral view. FIG. 14. Eumedonus zebra Alcock, 1895 . Male, 11.5Ö11.9 mm (SMF 21985): A, dorsal view; B, ventral view. number AC53 , Lubang Island , Station 34, 14ss01.0¾S, 120ss15.8 ¾E, 188±191 m , coll. MUSORSTOM, Philippines 1976 Expedition , 23 March 1976 . East China sea : One male, one female ( SMF TS161 ), coll. T . Sakai , Simoda Marine Biological Station , 1933 . Diagnosis . Carapace pentagonal, rostrum long, tip of rostrum not deēxed; surface of carapace covered with numerous granules and some fossae. Lateral carapace teeth very sharp, tip usually directed laterally; base of tooth more slender. Infraorbital tooth sharp. Subhepatic and suborbital regions highly tuberculated. Antero-external angle of merus of maxilliped 3 auriculiform. Surface of male thoracic sternum highly tuberculated; median part of male thoracic sternite 4 depressed. Male abdominal segment 7 depressed into abdominal groove; surface with numerous fossae. Chelipeds granulose with scattered setae; dorsal margin of palm usually with distinct lamelliform crests in females; carpus with distinct spine on distal inner angle; median, inner proximal and outer inner part of merus each with a strong tooth, tooth may be lamelliform; inner surface of basis-ischium with a large tooth which may be lamelliform. Anterior margins of ambulatory merus and carpus distinctly cristate; posterior margins of merus usually with two very distinct parallel crests; dactylus of leg 1 not much longer than those of other legs. G1 slender, sinuous; tip of G1 bent 45ss or 90ss. FIG. 15. Eumedonus zebra Alcock, 1895 . A±F, K, lectotype female, 7.3Ö8.1 mm (BMNH 1899.1.20.7): A, dorsal view of carapace; B, postero-dorsal view of left cheliped; C, sternum; D, face of carapace; E, fourth right ambulatory leg; F, left third maxilliped; K., third left ambulatory leg. G±J, L, Q, Male, 11.5Ö11.9 mm (SMF 21985): G, left G1; H, distal tip of left G1; I, right G2; J, abdomen; L, distal tip of right G2; Q, dorsal view of carapace (schematic). M±N, male, 13.4Ö14.1 mm (MNHN), ORSTOM number AC46: M, left G1; N, sternum. O±P, R, male, 11.8Ö11.8 mm (MNHN), ORSTOM number AC47±48: O, teeth on inner margin of chelipedal merus and carpus; P, infraorabital tooth; R, dorsal view of carapace (schematic). Scales for A±G, I±R= 1.0 mm; for H= 0.1 mm. Sexual dimorphism . In addition to the di erence in the degree of lamelliform crests on the palm, the proximal spine on the anterior margin of chelipedal merus is small in males but large in females (®gure 15B, O). Remarks . Gordon (1934) reported a specimen which is examined here ( BMNH 1899.1.20 . 7). This specimen is probably part of the syntype series of Alcock (1895) as it was indicated on the label that it was a gift from the Indian Museum. Also, the locality indicated on the label stated that the specimen was collected from the Andaman Sea, which is where the type locality ( Sri Lanka ) is situated. This specimen ( 7.3Ö 8.1 mm ) ( BMNH 1899.1.20 .7) is hereby designated as the lectotype of the species. Based on the descriptions and ®gures, specimens reported by Sakai (1938 , 1965 , 1976 ) are referred to E. zebra as well. Specimens collected by the MUSORSTOM in 1976 (from the Lubang Island, Philippines ) examined in the current study are probabl y part of the specimens reported by SereÁ ne and Vadon (1981), their specimens seem to ®t well into the current de®nition of the species. A pair of specimens deposited at the SMF , collected from the East China Sea in 1933 at the Simoda Marine Station, are probably part of the series of specimens examined by T . Sakai (1934 or possibly later). These specimens were reported as E. vicinus by Sakai (1934 , 1936 ) but were re-determined later as E. zebra by Sakai (1938) . We concur with his later identi®cation. Specimens reported by Monod (1938) as E. vicinus were re-examined and they are actually E. zebra . Some of the specimens (from Station X and Station XVII ) collected from the Suez Canal ( MNHN ) by Dollfus, however, are rather small and their identi®cation is di cult. The infraorbital teeth of these small specimens are not as sharp, the crests on the posterior margins of the ambulatory meri not as developed and the dorsal margin of the palm of the cheliped is less tuberculate. Adult characters, however, are very diagnostic and easily distinguish E. zebra from E. vicinus . The specimen from the La Reunion ( MNHN B-20412) is also a juvenile and its present identi®cation is somewhat tentative. Among the specimens examined in the current study, variation is observed in the angle of the distal tip of the G1, which is bent at 90ss (®gure 15G) or 45ss (®gure 15M). The forms of the rostrum and the lateral carapace teeth may also vary. Some specimens have a more V-shaped rostrum (®gure 15 R ) and others do not (®gure 15Q). The lateral carapace teeth are sometimes directed forward (more common) (®gures 15A, R ) or directed laterally (less common) (®gure 15Q). Di erences between E. zebra and E. vicinus , the closest species, have been discussed in the earlier section under E. vicinus . Distribution . From the Red Sea to the East China Sea.