Indian Journal of Geo Marine Sciences Vol. 46 (05), May 2017, pp. 982-985 First report of a deep sea spider crab, Encephaloides armstrongi WoodMason and Alcock, 1891 from Gujarat waters of India Gyanaranjan Dash*, Mohammed Koya K. & Nayan P. Makwana Veraval Regional Centre of CMFRI, Matsya Bhavan, Bhidia, Veraval: 362 269, Gujarat, India *[E-mail: gyanranjandashcmfri@gmail.com/gyanaranjan@cmfri.org.in] Received 17 September 2014 ; revised 14 January 2015 A single specimen of the male crab (3.0 cm carapace length and 3.8 g body weight) was collected from the incidental catch sample of a multiday trawler operating at a depth range of 107-132 m off Gujarat coast of India. The detailed morphometric measurements and diagnostic features with updated systematics have been presented in this paper. The crab has well devolved branchial region and thrive in the oxygen minimum zone of the sea. [Keywords: Deep sea spider crab, Encephaloides armstrongi, Veraval, Gujarat] Introduction Crabs are one of the benthic crustacean faunas and are exploited by fishing vessels mostly as incidental catch targeting valuable shrimp stocks of the coast. The species described here is identified as Encephaloides armstrongi and belongs to the family ‘Inachidae’. Earlier known distribution of the crab is shown in Figure 1. The crab was reported for the first time from Bay of Bengal in the north-east Indian Ocean1. Subsequently, the crab was reported from Gulf of Oman in the north-western Arabian Sea at a depth range of 171-311 m depth2 and off Oman coast at a depth range of 150-1000 m depth3. This is the first report of the crab from Gujarat waters of India, thus representing its distribution in northeastern Arabian Sea. Fig.1-Map showing distribution of Encephaloides armstrongi Wood-Mason and Alcock, 1891 Materials and Methods The present crab specimen was collected from a multiday trawler operating in a depth range of 30-135 m off Veraval coast of Gujarat, India. The Veraval Regional Centre of Central Marine Fisheries Research Institute (CMFRI) is continuously collecting information about the spatial and temporal distribution of fishery resources with the help of commercial fishing vessels, for which some randomly selected vessels are regularly provided with sample collection bags for the collection of geo-referenced fish catch, by-catch and discard samples from each haul. Present specimen was found in the by-catch sample of a trawler operating in an area from 19°19.625'N/ 69°47.870'E to 19°16.670'N/ 69°49.706'E at a depth range of 107-132 m. Morphometric measurements of the specimens were collected after which the specimen was preserved in 5 % formalin and kept in the institute museum for future reference. Specimen was identified following the description of Alcock4. The species was assigned its proper taxonomic position following the latest decapod crustacean classification scheme5. Results Systematics The detailed systematics following the classification scheme suggested by De Grave5 is given below. INDIAN J. MAR. SCI., VOL. 46, NO. 05, MAY 2017 Phylum: Arthropoda (von Siebold, 1848) Sub-phylum: Crustacea (Brunnich, 1772) Class: Malacostraca (Latreille, 1802) Sub-class: Eumalacostraca (Grobben, 1892) Order: Decapoda (Latreille, 1802) Suborder: Pleocyemata (Burkenroad, 1963) Infraorder: Brachyura (Linnaeus, 1758) Section: Eubrachyura (de Saint Laurent, 1980) Subsection: Heterotremata (Guinot, 1977) Super-family: Majoidea (Samouelle, 1819) Family: Inachidae (MacLeay, 1838) Genus: Encephaloides Wood-Mason and Alcock, 1891 Description of the specimen The specimen obtained was a male crab. The detail of the morphometric measurement taken from the specimen (Figure 2) and its comparison with the holotype1 is given in Table no 1. 983 post-ocular spine. There is a pair of antennae situated on either side of rostrum that can be seen dorsally. The merus of the external maxillipeds are modified into foliaceous ear shaped lobes, which cover the branchial orifice. The legs and chelipeds are slender, cylindrical and smooth. The first pair of legs is the longest. The carapace is pinkish yellow to brown and legs are pink in colour. Discussion The present crab specimen was identified as Encephaloides armstrongi1 by its characteristic beak like single rostrum, heart shaped carapace and slender legs. Earlier the crab was assigned under sub-family ‘Inachinae’ of family ‘Majidae3, 4 . But later, owing to its high diversity the family Fig. 2- Encephaloides armstrongi Wood-Mason and Alcock, 1891 caught off Gujarat Coast, India Identification characteristics The close up view of the specimen has been given in Figure 3. Carapace is heart shaped and its length (CL: from posterior edge of carapace to tip of rostrum) is almost equal to its breadth. Surface of the carapace is not smooth with minute nodules and bumps. The gastric and hepatic regions of the carapace are well defined but the cardiac and intestinal regions are covered by well-developed branchial regions, which bulge out to unit at the posterior midline of carapace. The rostrum is just like the beak of a bird and is finely serrated. Its length is about one fourth of the actual length of carapace. In male, the abdomen is having seven joints. The eyes are small, slender, poorly pigmented and are retractile against the side of the carapace. Supra-orbital edge is narrow, ending anteriorly in a minute tooth, and there is a small Fig.3-Close up view of Encephaloides armstrongi WoodMason and Alcock, 1891 caught off Gujarat Coast, India (A: profile view, B: Dorsal view and C: Ventral view) 984 DASH et al.: FIRST REPORT OF A DEEP SEA SPIDER CRAB, ENCEPHALOIDES ARMSTRONGI ‘Majidae’ was reclassified as superfamily ‘Majoidea’ and the sub-family ‘Inachinae’ was elevated to family ‘Inachidae5,6. The crab has already been reported from Bay of Bengal at a depth range of 162-185 m1, gulf of Oman, northwestern Arabian Sea at a depth range of 171-311 m depth2 and off Oman coast at a depth range of 150-650 m depth3. Table 1. The morphometric measurements of the present specimen of Encephaloides armstrongi Wood-Mason and Alcock, 1891 (weight: 3.8 g) caught off Gujarat Coast of India compared with the earlier report (Alcock, 1899) Morphometric characters Measurements (cm) Proportion to carapace length Present specimen Referred specimen Carapace width 2.9 ≈1.0 ≈1.0 Carapace length 3.0 1.0 1.0 Abdomen width 0.6 Abdomen length 1.2 Cheliped length 4.8 1.6 2.0 Cheliped Propodus length 2.4 Cheliped Propodus height 0.3 Cheliped Propodus width 0.2 Cheliped Dactylus length 0.6 st 9.7 3.2 4.5-5.0 nd 8.6 2.9 4.0-4.5 rd 6.4 2.1 2.8-3.0 th 4.6 1.5 1.7 1 walking leg length 2 walking leg length 3 walking leg length 4 walking leg length The present occurrence of E. armstrongi from Gujarat waters of India is the first report of the crab from north-eastern Arabian Sea. The crab is usually found in the oxygen minimum zone (OMZ) and has well devolved branchial region, which seems to be an adaption to thrive in oxygen deficient zone where the biodiversity is usually low. The OMZ of sea facilitate large-scale degradation of organic matter sinking from highly productive surface water and thus provides abundant food supply for the dwelling organisms7. E. armstrongi is a highly mobile crab and possibly plays its role in the ecosystem by resuspending fine organic material from the sea surface and helping in the process of decomposition by burying the deposited organic matter8. The long legs and rostrum could be attributed to the above-mentioned functionality of the crab. Conclusion The present report is the 4th known world report and first recorded geographic distribution of the spider crab, Encephaloides armstrongi from north-eastern Arabian Sea as well as from entire west coast of India. The report provides valuable information about the biodiversity and the ecological significance of benthic fauna in the marine ecosystem. Acknowledgement Authors are thankful to Indian Council of Agricultural Research (ICAR) for providing financial assistance to carry out the research work. The authors wish to express their gratitude to Dr. A. Gopalakrishnan, the Director, Central Marine Fisheries Research Institute (CMFRI), India for providing the facilities at the centre for conducting the above study. References 1 2 3 4 Wood-Mason, J. & Alcock, A., Natural history notes from H. M. Indian Marine Survey Steamer ‘Investigator’, Commander R. F. Hoskyn, R.N., commanding. No. 21. Note on the results of last seasons dredging, Annals and magazine of natural history 39(1891) 258-271. Griffin, D.J.G., Spider crabs (Crustacea: Brachyura: Majidae) from the International Indian Ocean Expedition, 1963-1964, Smithsonian Contributions to Zoology 182(1974) 1-35. Creasey, S., Rogers, A.D., Tyler, P., Young, C. & Gage J., The population biology and genetics of the deep-sea spider crab, Encephaloides armstrongi Wood-Mason 1891 (Decapoda: Majidae), Philosophical Transactions of the Royal Society of London B 352(1997) 365-379. Alcock, A., An account of the deep-sea Brachyura collected by the royal Indian marine survey ship INDIAN J. MAR. SCI., VOL. 46, NO. 05, MAY 2017 5 ‘Investigator’, (Trustees of the Indian Museum, Calcutta, India) 1899, pp. 85. De Grave, S., Pentcheff, N.D., Ahyong, S.T., Chan, T.Y., Crandall, K.A., Dworschak, P.C., Felder, D.L., Feldmann, R.M., Fransen, C.H.J.M., Goulding, L.Y.D., Lemaitre, R., Low, M.E.Y., Martin, J. W., Ng, P.K.L., Schweitzer, C.E., Tan, S.H., Tshudy, D. & Wetzer, R., A classification of living and fossil genera of decapod crustaceans. Raffles Bulletin of Zoology Supplement No. 21(2009) 1-109. 6 7 8 985 Martin, J.W. & Davis, G.E. An updated classification of the Recent Crustacea. Natural History Museum of Los Angeles County, Science Series 39(2001) 1-124. Wishner K., Levin L., Gowing M. & Mullineaux L., Involvement of the oxygen minimum in benthic zonation on a deep seamount. Nature, 346(1990) 57-59. Demopoulos, A.W.J., Smith, C.R. & Tyler, P.A., The deep Indian Ocean floor, in: Ecosystems of the Deep Oceans, edited by P.A. Tyler, (Elsevier Science, Amsterdam, the Netherlands) 2003, pp. 219-238.