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First Report of a Deep Sea Spider Crab, Encephaloides Armstrongi Wood- Mason and Alcock, 1891 from Gujarat Waters of India

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First Report of a Deep Sea Spider Crab, Encephaloides Armstrongi Wood- Mason and Alcock, 1891 from Gujarat Waters of India Indian Journal of Geo Marine Sciences Vol. 46 (05), May 2017, pp. 982-985 First report of a deep sea spider crab, Encephaloides armstrongi Wood- Mason 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: [email protected]/[email protected]] 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 Materials and Methods Crabs are one of the benthic crustacean faunas The present crab specimen was collected from and are exploited by fishing vessels mostly as a multiday trawler operating in a depth range of incidental catch targeting valuable shrimp stocks 30-135 m off Veraval coast of Gujarat, India. The of the coast. The species described here is Veraval Regional Centre of Central Marine identified as Encephaloides armstrongi and Fisheries Research Institute (CMFRI) is belongs to the family ‘Inachidae’. Earlier known continuously collecting information about the distribution of the crab is shown in Figure 1. The spatial and temporal distribution of fishery crab was reported for the first time from Bay of resources with the help of commercial fishing Bengal in the north-east Indian Ocean1. vessels, for which some randomly selected vessels Subsequently, the crab was reported from Gulf of are regularly provided with sample collection Oman in the north-western Arabian Sea at a depth bags for the collection of geo-referenced fish range of 171-311 m depth2 and off Oman coast at catch, by-catch and discard samples from each a depth range of 150-1000 m depth3. This is the haul. Present specimen was found in the by-catch first report of the crab from Gujarat waters of sample of a trawler operating in an area from India, thus representing its distribution in north- 19°19.625'N/ 69°47.870'E to 19°16.670'N/ eastern Arabian Sea. 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 Fig.1-Map showing distribution of Encephaloides armstrongi classification scheme suggested by De Grave5 is Wood-Mason and Alcock, 1891 given below. INDIAN J. MAR. SCI., VOL. 46, NO. 05, MAY 2017 983 Phylum: Arthropoda (von Siebold, 1848) post-ocular spine. There is a pair of antennae Sub-phylum: Crustacea (Brunnich, 1772) situated on either side of rostrum that can be seen Class: Malacostraca (Latreille, 1802) dorsally. The merus of the external maxillipeds Sub-class: Eumalacostraca (Grobben, 1892) are modified into foliaceous ear shaped lobes, Order: Decapoda (Latreille, 1802) which cover the branchial orifice. The legs and Suborder: Pleocyemata (Burkenroad, 1963) chelipeds are slender, cylindrical and smooth. The Infraorder: Brachyura (Linnaeus, 1758) first pair of legs is the longest. The carapace is Section: Eubrachyura (de Saint Laurent, 1980) pinkish yellow to brown and legs are pink in Subsection: Heterotremata (Guinot, 1977) colour. Super-family: Majoidea (Samouelle, 1819) Family: Inachidae (MacLeay, 1838) Discussion Genus: Encephaloides Wood-Mason and The present crab specimen was identified as Alcock, 1891 Encephaloides armstrongi1 by its characteristic beak like single rostrum, heart shaped carapace Description of the specimen and slender legs. Earlier the crab was assigned The specimen obtained was a male crab. The under sub-family ‘Inachinae’ of family ‘Majidae3, detail of the morphometric measurement taken 4. But later, owing to its high diversity the family from the specimen (Figure 2) and its comparison with the holotype1 is given in Table no 1. 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 Fig.3-Close up view of Encephaloides armstrongi Wood- carapace. Supra-orbital edge is narrow, ending Mason and Alcock, 1891 caught off Gujarat Coast, India (A: profile view, B: Dorsal view and C: Ventral view) anteriorly in a minute tooth, and there is a small 984 DASH et al.: FIRST REPORT OF A DEEP SEA SPIDER CRAB, ENCEPHALOIDES ARMSTRONGI ‘Majidae’ was reclassified as superfamily depth range of 162-185 m1, gulf of Oman, north- ‘Majoidea’ and the sub-family ‘Inachinae’ was western Arabian Sea at a depth range of 171-311 elevated to family ‘Inachidae5,6. The crab has m depth2 and off Oman coast at a depth range of already been reported from Bay of Bengal at a 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) Proportion to carapace length Morphometric characters Measurements (cm) 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 1st walking leg length 9.7 3.2 4.5-5.0 2nd walking leg length 8.6 2.9 4.0-4.5 3rd walking leg length 6.4 2.1 2.8-3.0 4th walking leg length 4.6 1.5 1.7 The present occurrence of E. armstrongi from the ecological significance of benthic fauna in the Gujarat waters of India is the first report of the marine ecosystem. crab from north-eastern Arabian Sea. The crab is usually found in the oxygen minimum zone Acknowledgement (OMZ) and has well devolved branchial region, Authors are thankful to Indian Council of which seems to be an adaption to thrive in oxygen Agricultural Research (ICAR) for providing deficient zone where the biodiversity is usually financial assistance to carry out the research work. low. The OMZ of sea facilitate large-scale The authors wish to express their gratitude to Dr. degradation of organic matter sinking from highly A. Gopalakrishnan, the Director, Central Marine productive surface water and thus provides Fisheries Research Institute (CMFRI), India for abundant food supply for the dwelling providing the facilities at the centre for organisms7. E. armstrongi is a highly mobile crab conducting the above study. and possibly plays its role in the ecosystem by re- suspending fine organic material from the sea References surface and helping in the process of 1 Wood-Mason, J. & Alcock, A., Natural history notes decomposition by burying the deposited organic from H. M. Indian Marine Survey Steamer ‘Investigator’, 8 Commander R. F. Hoskyn, R.N., commanding. No. 21. matter . The long legs and rostrum could be Note on the results of last seasons dredging, Annals and attributed to the above-mentioned functionality of magazine of natural history 39(1891) 258-271. the crab. 2 Griffin, D.J.G., Spider crabs (Crustacea: Brachyura: Majidae) from the International Indian Ocean Expedition, Conclusion 1963-1964, Smithsonian Contributions to Zoology th 182(1974) 1-35. The present report is the 4 known world 3 Creasey, S., Rogers, A.D., Tyler, P., Young, C. & Gage report and first recorded geographic distribution J., The population biology and genetics of the deep-sea of the spider crab, Encephaloides armstrongi spider crab, Encephaloides armstrongi Wood-Mason from north-eastern Arabian Sea as well as from 1891 (Decapoda: Majidae), Philosophical Transactions of the Royal Society of London B 352(1997) 365-379. entire west coast of India. The report provides 4 Alcock, A., An account of the deep-sea Brachyura valuable information about the biodiversity and collected by the royal Indian marine survey ship INDIAN J. MAR. SCI., VOL. 46, NO. 05, MAY 2017 985 ‘Investigator’, (Trustees of the Indian Museum, Calcutta, 6 Martin, J.W. & Davis, G.E. An updated classification of India) 1899, pp. 85. the Recent Crustacea. Natural History Museum of Los 5 De Grave, S., Pentcheff, N.D., Ahyong, S.T., Chan, T.Y., Angeles County, Science Series 39(2001) 1-124. Crandall, K.A., Dworschak, P.C., Felder, D.L., 7 Wishner K., Levin L., Gowing M. & Mullineaux L., Feldmann, R.M., Fransen, C.H.J.M., Goulding, L.Y.D., Involvement of the oxygen minimum in benthic zonation Lemaitre, R., Low, M.E.Y., Martin, J.
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