488-491A survey was conducted to study the distribution of brachyuran crabs along the coast of south Andaman Island during 2015-2018. The investigation confirmed the occurrence of Atergatis ocyroe (Herbst, 1801) from the Port Blair Coast of Andaman &amp; Nicobar Islands, India. From a comprehensive study of standard literature, it was evident that A. ocyroe was misidentified as A. floridus and these two species do not co-exist in the same geographical area. Hence, the existence of A. floridus in Andaman and Nicobar Islands is doubtful. The confirmed distributional record of A. ocyroe across the Indian Ocean is provided and discussed with its taxonomy, and detailed description along with photograph and line diagram is provided in this study

Meher, Balakrishna

Thiruchitrambalam, Ganesh

English

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Indian Journal of Geo Marine Sciences Vol. 49 (3), March 2020, pp. 488-491    Short Communication   Clarification note on taxonomic identification of Atergatis ocyroe (Herbst, 1801) (Crustacea: Decapoda: Xanthidae): New distributional record from the Port Blair coast, Andaman & Nicobar Islands, India Balakrishna Meher & Ganesh Thiruchitrambalam* Department of Ocean Studies & Marine Biology, Pondicherry University, Brookshabad Campus, Port Blair-744 112,  Andaman & Nicobar Islands, India *[Email: ganesht.omb@pondiuni.edu.in] Received 04 September 2018; revised 30 October 2018 A survey was conducted to study the distribution of brachyuran crabs along the coast of south Andaman Island during 2015-2018. The investigation confirmed the occurrence of Atergatis ocyroe (Herbst, 1801) from the Port Blair Coast of Andaman & Nicobar Islands, India. From a comprehensive study of standard literature, it was evident that A. ocyroe was misidentified as  A. floridus and these two species do not co-exist in the same geographical area. Hence, the existence of A. floridus in Andaman and Nicobar Islands is doubtful. The confirmed distributional record of A. ocyroe across the Indian Ocean is provided and discussed with its taxonomy, and detailed description along with photograph and line diagram is provided in this study.  [Keywords: Andaman & Nicobar Islands, Atergatis ocyroe,      New distributional record, Xanthidae] Introduction In India, a total of 931 species of brachyuran crabs have been reported1. Among them, Xanthidae is one of the most diverse families consisting of 140 species and 48 genera1. Atergatis floridus (Linnaeus, 1767) belong to the family Xanthidae and is commonly known as ‘shawl crab’ because of shawl like fine reticulated mark on the surface of the carapace2. It is a poisonous crab as it may contain lethal neurotoxin (tetrodotoxin; TTX)3. The Atergatis ocyroe (Herbst, 1901) was earlier considered as the junior synonym of Atergatis floridus (Linnaeus, 1767) but Ng & Davie (2007)2 revised the taxonomy of Atergatis floridus (Linnaeus, 1767) and recognized Atergatis ocyroe (Herbst, 1801) as a valid species. These two species can be very easily distinguished by colour pattern on the surface of carapace i.e. A. floridus (Linnaeus, 1767) with shawl-like fine reticulated mark whereas, A. ocyroe (Herbst, 1901) with large blotches or spots2. The splitting of  A. ocyroe (Herbst, 1801) and A. floridus (Linnaeus, 1767) has created an uncertainty about the distribution of these two species. To know the proper geographical distribution of these two species reassessment is necessary. The objective of the present study is to verify and confirm the identity of the concerned species in Andaman and Nicobar Islands.  Material and methods The specimen was collected from the rocky intertidal region of Burmanallah which is located at the east coast of Port Blair, Andaman and Nicobar Islands. Hand picking method was followed for collecting the specimen. For preservation, 10 % formalin was used. Standard literature was used for taxonomic identification2,4. After identification of specimen, photographs were taken and line diagrams were prepared. The specimen was deposited at Zoological Survey of India, National Zoological Collections of A & N Regional Centre, Port Blair. The distributional map of A. ocyroe is prepared on the basis of the present study and the available literature showing confirm occurrence of the species.  Results During the period of study (January 2015 - June 2018) five individuals of A. ocyroe were collected at low-waterline of the rocky intertidal region of Burmanallah, South Andaman Islands (Fig. 1). The occurrence of A. ocyroe is reported as new distributional record to the Andaman & Nicobar Islands.  Systematics Order – Decapoda Latreille, 1802 Infra-order – Brachyura Linnaeus, 1758 Family –Xanthidae Mac Leay, 1838 Subfamily – Zosiminae Alcock, 1898 Genus – Atergatis De Haan, 1833 Atergatis ocyroe (Herbst, 1801)  Material examined One female specimen (ZSI/ANRC-20309)  (CL - 30.59 mm, CW - 45.32 mm), Burmanallah,  South Andaman Islands, India (2nd May 2018; 92°43'892'' E, 11°35'225'' N).  Description Carapace sub-oval and remarkably convex; carapace length about 2/3rd of greatest breadth of MEHER & THIRUCHITRAMBALAM: CLARIFICATION NOTE ON TAXONOMIC IDENTIFICATION OF A. OCYROE   489carapace; regions not well defined; surface smooth, hair-free, lumpy and with large  blotches  and/or spots (Figs. 2a, 3a). Front bi-lobed; nearly 1/4th of greatest breadth of carapace and roughly make a semicircle with the anterolateral margin. Orbit small, round margin with two fissures. Eyestalk thick, very short and never exceed beyond the orbital margin. Antennule folded horizontally and remains concealed under the roof of the front. Antenna with very short flagella. Pterygostomial region with a smooth surface. Anterolateral border very strongly arched with a keel-like edge which cut into three broad lobes by fine fissures, the third lobe broader than the second lobe and the first least broad; a well-defined blunt tooth at the epibranchial angle. Cheliped massive and subequal, the right one slightly larger than left one; upper border of meruscrest-like, inner and outer surface smooth but faint reticulated structure can be observed  on  outer  surface;   carpus with smooth and  considerably convex outer surface; the upper margin of dactylus crest-like, a longitudinal channel on outer surface of both dactylus and fixed finger, both finger    Fig. 1 — Map showing confirm distributional record of Atergatis ocyroe (Herbst, 1801) across the Indian Ocean with a new distributional record at Burmanallah coast of south Andaman Islands.  INDIAN J. GEO-MAR. SCI., VOL. 49, NO. 03, MARCH 2020   490with interlocking teeth. External maxillipeds without hair on the surface but inner border densely lined with small hairs especially in ischium; ischium longitudinally rectangular; and the length of ischium twice the length of merus (Figs. 2b, 3b). Walking leg laterally compressed; the merus of first pair of leg slightly wider than merus of last pair, merus breadth of 2nd and 3rd pair of legs equal to each other and less wider than that of 1st and last pair of legs; a small patch of dense setae on the distal part of lower border of propodus; the upper and lower border of dactylus also densely covered with setae.  Key to identification of Atergatis floridus and A. ocyroe Carapace suboval, convex; surface smooth, lumpy; regions poorly indicated; a blunt tooth at epibranchial  angle ...........................................................................1 1. A fine reticulated shawl-like color pattern on the surface of carapace; branchial region of the carapace comparatively more swollen; ischium of the third maxilliped comparatively more quadrate …………………………………………...  A. floridus - Large spots or blotches on carapace; branchial region of the carapace comparatively lower; ischium of the third maxilliped clearly more longitudinally rectangular ………………………………... A. ocyroe  A comparative taxonomic account of A. floridus and A. ocyroe Characters A. floridus A. ocyroe  Carapace A fine reticulated shawl-like color pattern on the surface of carapace.  Large spots or  blotches on  carapace.  Branchial region Branchial region of the carapace comparatively more swollen.  Branchial region  of the carapace comparatively lower.  Ischium Ischium of the third maxilliped comparatively more quadrate.  Ischium of the third maxilliped clearly more longitudinally rectangular.  Distribution South east Asia (except Andaman  sea) , West Pacific and Australia Northern and western Indian Ocean.  Discussion There are very few confirmed distributional records of Atergatis ocyroe (Herbst, 1801) across the Indian Ocean. Ng & Davie2 reported from Phuket (Thailand), Pakistan, Sri Lanka, South Africa, Gulf of Mannar (India); Ghotbeddin and Naderloo4, and Naderloo et al.5 reported from the Gulf of Oman (Iran); Trivedi and Vachhrajani6 from Saurashtra coast of Gujarat state, (India) (Fig. 1). According to Ng & Davie2 all Southeast Asia (with the exception of the Andaman Sea and perhaps the west coast of Sumatra), West Pacific and Australia are A. floridus and records from northern and western Indian Ocean are A. ocyroe. He also suggested that to ascertain precise geographical boundaries between the two species, more work needs to be done especially in the area of Andaman Sea and the beginning of Straits of Malacca, perhaps Parts of Northern Australia and isolated islands in the Indian Ocean. So in the present work, an attempt was made to provide a new distributional record of A. ocyroe across the Andaman Sea. The specimens of A. ocyroe collected from Port Blair coast well agree with the description of Ng & Davie2 and Ghotbeddin & Naderloo4. The absence of a shawl-like fine reticulated mark and presence of large blotches on carapace confirm its identity.  Conclusion This study confirms the occurrence of A. ocyroe in Andaman Islands and report as new record to this region. Based on standard literature, it was observed that A. ocyroe and A. floridus do not co-exist in the same geographical area. Hence, the occurrence of  A. ocyroe in Port Blair coast creates a question    Fig. 2 — Atergatis ocyroe (Herbst, 1801) scale bar 1 cm(a) dorsal view (b) ventral view   Fig. 3 — Atergatis ocyroe (Herbst, 1801) (a) dorsal view, scalebar 1 cm (b) external maxillipeds, scale bar 2 mm.   MEHER & THIRUCHITRAMBALAM: CLARIFICATION NOTE ON TAXONOMIC IDENTIFICATION OF A. OCYROE   491mark on the existence A. floridus in Andaman & Nicobar Islands.   Acknowledgment Authors are thankful to the Authorities of Pondicherry University for providing the necessary facilities to carry out this work and University fellowship to Balakrishna Meher. Authors also show their sincere gratitude to Zoological survey of India, Andaman and Nicobar Regional Centre, Port Blair for providing help during the study.  References 1 Dev Roy M. K., An inventory of decapods crustaceans from India, J. Environ. & Sociobiol., 11 (2) ( 2014) 219-274. 2 Ng, P. K. L. & Davie, P. J. F., On the identity of Atergatis floridus (Linnaeus, 1767) and recognition of Atergatis ocyroe (Herbst, 1901) as a valid species from the Indian Ocean (Crustacea: Brachyura: Xanthidae), Raff. Bull. Zool., 16 (2007) 169–175. 3 Noguchi, T., Jeon, J. K., Arakawa, O., Sugita, H., Deguchi, Y, Shida, Y. & Hashimoto, K., Occurrence of tetrodotoxin and anhydrotetrodotoxin in Vibrio sp. isolated from the Intestines of a Xanthid Crab, Atergatis floridus, J. Biochem, 99 (1996) 311-314. 4 Ghotbeddin, N. & Naderloo R., Confirming of the occurrence of three intertidal xanthid crabs (Crustacea: Decapoda: Brachyura: Xanthidae) in the Gulf of Oman, Mar. Biodivers. Rec., 7 (98) (2014) 1-5. 5 Naderloo, R., Ebrahimnezhad, S. & Sari, A.,  Annotated checklist of the decapod crustaceans of  the Gulf of Oman, northwestern Indian Ocean, Zootaxa, 4028 (3) (2015) 397–412. 6 Trivedi, J. N. & Vachhrajani, K. D., On identity of  Atergatis ocyroe (Herbst, 1801) (Crustacea: Brachyura: Xanthidae) in Indian waters. Int. J. Fauna Biol. Stud., 3 (2) (2016) 62-64.       

Clarification note on taxonomic identification of Atergatis ocyroe (Herbst, 1801) (Crustacea: Decapoda: Xanthidae): New distributional record from the Port Blair coast, Andaman & Nicobar Islands, India

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Clarification note on taxonomic identification of Atergatis ocyroe (Herbst, 1801) (Crustacea: Decapoda: Xanthidae): New distributional record from the Port Blair coast, Andaman & Nicobar Islands, India

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