Page 1 CRUSTACEAN RESEARCH, NO. 22 : 7-10, 1993 a New Deep-Sea Crab, Genus Chaceon, from the Austral Islands, Southwestern Pacific Ocean (Decapoda: Geryonidae) Raymond B

CRUSTACEAN RESEARCH ，NO. 22: 7-10 ， 1993

A new deep-sea crab ，genus Chaceon ，from the Austral Islands ， southwestern southwestern Pacific Ocean (Decapoda: Geryonidae)

Raymond B. Manning

Abstract. Abstract. - Chaceon australis ， the sixth 144 0 15. 5'W ， depth 870 meters ，trap ，leg. J. species species of the genus recorded from local- Poupin (SCMB) ，sta. 431 ， 17 August 1991: ities ities in the Pacific Ocean ， is described. It 2 males ， 78 x 93 mm and 83 x 97 mm (l ar- most closely resembles C. poupini ger is holotype ，MP ， smaller is paratype ， Manning ，from the 恥farquesas Islands ， USNM 264722) ，1 ovigerous female ，70 x but but has a smoother carapace ，shows differ- 85 mm (paratype ，MP). ences in relative distances between the anterolateral anterolateral teeth of the carapace ，has a Diagnosis. - A medium-sized Chaceon ， distal distal spine on the merus of the walking cl to 83 mm ，cb to 98 mm ， with low but legs ，and has a different color in life. distinct frontal and anterolateral teeth on the the carapace and with laterally compressed The species described below is the second dactyli on the walking legs. Carapace 1.2 undescribed undescribed species of Chaceon to be dis- times wider than long ， moderately in f1 ated ， covered covered by J. Poupin ， Service Mixte de surface of protogastric and branchial Contrδle Biologique (SCMB) ，Tahiti ，dur- regions pitted and in f1 ated ， hepatic region ing ing exploratory trapping surveys in French smooth. Median pair of frontal teeth short Polynesia; Polynesia; see Poupin et al. (1 990) and but extending beyond lateral frontal teeth. Poupin & Buat (1992) for background on First ， third and fifth anterolateral teeth this this work. The first species ， C. poupini ， distinct but low ， not spiniform; second from the Marquesas Islands ，was named by tooth low ，obtuse ， fourth obsolete; distance me in 1992. The material from Rapa report- from first to third tooth greater than dis- ed here was examined a仇er that account had tance from third to 目白 h tooth. Orbit shal- gone to press. low ， with posterior incision; suborbital Abbreviations Abbreviations used below include: cb ， tooth sharp ， not extending to level of lateral carapace carapace width including anterolateral frontal tooth; suborbital margin evenly spines; spines; cl ， carapace length on midline; P5 ， curved ， smooth. Third maxilliped lacking fifth fifth pereopod (fourth walking leg). All projecting outer distal lobe on merus. measurements are in millimeters (mm). The Cheliped: merus with sharp dorsal spine types types have been deposited in the Museum subdistally ， lacking distal spine; carpus National National d'Histoire Naturelle ， Paris (MP) roughened dorsally ， lacking outer spine ， and the National Museum of Natural His- anterior margin tuberculate ， inner spine tory ，Washington (USNM). strong; propodus sparsely tuberculate ， with distal distal dorsal spine. Dactyli of walking legs latera l1 y compressed ， height at midlength Chaceon australis new species distinctly greater than width. P5: merus 5.9 Figs.I -2 6.0 times longer than high ， 0.8 times cb in Material. Material. - French Polynesia: Rapa ， males ，0 .6 times cb in female ， with distal ， Austral Austral Islands (Tubuai Islands) ，2T35. 3'S ， dorsal spine in male (spine obsolete in 「

8 R .B. MANNING

Fig . 1. Chaceon australis new species ， male holotype ，cl 83 mm: a ，dorsal view; b，carapace ，enlarged; c， front front and buccal area ，ventral view. NEW DEEPδEA CRAB 9

Fig.2. Fig.2. Chaceon australis new species ， male holotype ，CI 83 mm : a， P5; b，cheliped. female); female); carpus with line of low granules Remarks. - Five other species of dorsally; dorsally; propodus longer than dactylus ， Chaceon are now recognized from localities 4.5-4.8 4.5-4.8 (mean 4 .6) times longer than high. in the Pacific Ocean. Of the five ， only one ， Telson Telson length 0.6 times width in males. C. granulatus (Sakai ， 1978) ，from Japan ， has has dorsoventrally depressed dactyli on the Size -. Males ， cl 78 and 83 mm ，cb 93 walking legs; they are lat 巴rally compressed and 97 mm ; ovigerous female cl 70 mm ，cb in in C. australis. Chaceon australis differs 85 85 mm . Other measurements of ovigerous from both C. imperialis Manning ， 1992 ， female: female: P5 merus ， length 50.8 ， height 8.4; from the Emperor Seamount chain in the propodus ， length 33.3 ， height 6.9; dactyl us northern northern Pacific and C. yaldwyni Manning ， length length 32 .4， height 2.2 ， width 1. 2. Telson of Dawson and Webber ， 1990 ， from New smaller smaller male ， length 9.1 ， width 14.7 . Zealand ， in lacking sharp ， well developed Color -. In life ， most of carapace and antero1ateral teeth on the carapace in adults ， legs legs pink or light purple ， branchial regions and further agrees with C. yaldwyni in tan . having a distal dorsa1 spine on the merus of 10 10 R. B. MANNING the the walking legs. Chaceon australis resem- Acknowledgments bles bles C. bic%r Manning & Holth 山s，1989 ， from the Loyalty Islands ，New Caledonia ， 1 am indebted to Joseph Poupin for sav- and Australia 司 in having a bicolored cara- ing samples of this species and to Alain pace ，but differs in having much slenderer Crosnier for making the specimens available legs. legs. Chaceon australis most closely resem- for study. The figures were prepared for bles bles C. poupini Manning ，1992 ，from the publication by Lilly King Manning. Marquesas Islands. but differs in having (1) a smoother carapace with larger frontal and anterolateral anterolateral spines ， (2) a longer and Literature Cited sharper sharper suborbital tooth ‘ (3) low tubercles Manning ，R. 8.， 1992. Two new species of the (or (or large granules) on the carpus of the deep-sea crab genus Chaceon from the Pacific Ocean (Crustacea Decapoda Brachyura). Bulle- walking legs ，and (4) the second anterolater- tin du Museum National d'Histoire Naturelle ， al al tooth on the carapace much closer to the series 4， 14 (A ，1): 209-215 first-in first-in australis the distance form the 一一一， Dawson ， E. W. & Webber ， R. W. ，1990. A C. C. new species of Chaceon from New Zea1and first first to second tooth is more than half the (Crustacea: Decapoda: Geryonidae). Proceed- distance distance from the second to the third ，where- ings of the Bio1ogica1 Society of Washington ， 103 103 (3): 602 -607. as as in C. poupini the space between the first ，& Holthuis ， L. 8.， 1989. Two new genera and second tooth is less than half that and nine new species of geryonid crab (Crus- tacea ，Decapoda ，Geryonidae). Proceedings of between the second and third. The species the the Bio10gical Society of Washington ， 102 (1) ・ from Rapa also differs from C. poupini in 50 - 77. color in life ，being light purple or pink and Poupin ，J. ，Tamaril ， T. & Vandenboomgaerde ，A. ， 1990. 1990. Peches profondes aux casiers sur les tan tan rather than red overal l. pentes ocaaniques des iles de Po1ynesie The distal spine on the merus of the Francaise (N/O Marara -1986 /1989). Notes et Documents Documents Oceanographiques ORSTOM ， 42: walking legs is worn down in the female; it l→ 97 ，pls. 1- 3 (color). is is much more prominent in the males. 一一-，& Buat ，P. ， 1992. Discovery of deep-sea crabs crabs (Ch α ceon sp.) in French Po1ynesia Name. 一一 The name is from the Latin ， (Decapoda: Geryonidae). Journal of Crusta- cean cean Biology ， 12 (2): 270-281 australis ，southern ， referring to the southern Sakai ， T.， 1978. Decapod Crustacea from the occurrence of this species as well as its Emperor Seamount Chain. Researches on origin origin from the Austral Islands. Crustacea ，Carcinological Society of Japan ，8 1- 39 ，pls. 1-4. Distribution. Distribution. - Known only from the Austral Austral Islands ，southwestern Pacific Ocean. Department Department of 1nvertebrate Zoology ， Nationa1 Museum of Natura1 History ， Smithsonian Institu- tion ，Washington ， D. C. 20560 ，USA.