Indian Journal of Geo Marine Sciences Vol. 47 (09), September 2018, pp. 1888-1892

First record of a flathead from Chilika lagoon, Bay of Bengal

Debasish Mahapatro1*, R.C.Panigrahy 1, Sudarsan Panda2, Rajani K. Mishra.3, Dipti Raut 4 & Subodh K.Karna 5 1Department of Marine Sciences, Berhampur University, Odisha, India 2RCCF,Angul, Odisha 3National Centre for Antarctic and Ocean Research (NCAOR), MoES, Goa, India 4Department of Zoology, Ravenshaw University, Cuttack, Odisha, India 5Department of Zoology, Utkal University, Bhubaneswar, Odisha, India

*[E-mail: [email protected]]

Received 01 December 2016; revised 02 March 2017

Present study provides first ever prevalence report of two numbers of flat head lobster of species orientalis (: Scyllaridae) from Chilika lagoon. Small sized lobster (12.1 cm) was collected from Magarmukh area (19°41'48.14"N & 85°24'47.96"E) whereas larger specimen (16.2 cm) was observed from Shipakuda region (19°39'54.51"N & 85°29'13.41"E). Occurrence of this species is of great socio-economic significance since; it is used as dietary delicacy in southern India and abroad.

[Keywords: Flathead lobster, Thenus orientalis, Chilika lagoon, Bay of Bengal]

Introduction the northwest and southeast coasts of India6. In Bay of Although, extensive studies were carried out on Bengal, the species has been reported from waters of large benthic such as palinurid and Andaman and Nicobar Islands, Shoal Bay, Tamil nephropid , less information is available on nadu coast, West Bengal coast and Gulf of Mannar7. the scyllarid lobsters. This constituting over 70 Investigations on bottom dwelling fish and species in the world oceans1, 2. Out of seven genera of shellfish of Chilika lagoon8 revealed the presence of Scyllaridae, the genus Thenus has great socio- two species of lobsters such as ornatus and economic significance3, 4. Species representatives Panulirus polyphagus. However, the occurrence of belonging to Scyllaridae are commonly found in Thenus sp. from North-West coast of Bay of Bengal tropical waters ranged from Indian Ocean, Western particularly from a brackish water coastal ecosystem Pacific region, coasts of India, East coast of Africa such as Chilika lagoon is suggestive of a range (southern Red Sea to Natal) to China, Southern Japan, extension of the flat had lobster of Thenus orientalis. the Philippines and tropical Australia i.e. Western The present study described first record of flat head Australia to Queensland. Seven species under this lobsters from two regions of Chilika lagoon. genus have been reported so far. These are popularly known by their common names such as shovel nosed Materials and Methods lobsters, slipper lobsters, flathead lobsters, Moreton Chilika (lat 19° 28' and 19° 54' N; long 85° 05' and Bay bugs, sand bug and mud bug etc. The broad 85° 38' E), the largest brackish water lagoon of flattened cephalothorax of the genera Thenus is Asia located at the North West coast of Bay of Bengal considered to be peculiar characterizing this genus (Fig. 1A), is one of the hotspots of biodiversity and thereby differentiating it from other lobster genera3. provides an exceptional habitat for migratory birds, Common representatives of the Indo-Pacific region Irrawaddy dolphins, rare, vulnerable and endangered are T. orientalis, T. indicus, T. unimaculatus, T. species listed in the IUCN red list9. The lagoon is parindicus and T. australiensis5. Significant studies at shallow (average depth 1.2 m) comprising four the generic level5 established that Thenus orientalis hydrographically distinct sectors such as the northern was earlier misidentified as T. unimaculatus1,2 in the fresh water region, central and southern brackish Indian subcontinent. Furthermore, available literature water region and marine influenced outer channel describes the range distribution of T. unimaculatus to sector. It is connected to the Bay of Bengal through MAHAPATRO et al.: First RECORD OF A FLATHEAD LOBSTER FROM CHILIKA LAGOON 1889

Fig. 1 — Map showing global distribution of Thenus orientalis (A), Map showing India, Odisha and Chilika lagoon having four sectors (B), Map showing the region of collection from Chilika lagoon two lagoon inlets. The lagoon has been subject to Family: Scyllaridae ecological stresses attributable to natural and Genus: Thenus anthropogenic alterations9. Species: T. orientalis Lund, 1793 (Table 1; Fig. 2 A&B) Results Synonyms : The live specimen was obtained through trap Sagaritis orientalis Billberg, 1820, Scyllarus of indigenous made having the mesh size of 2.5 cm. orientalis Lund, 1793, First specimen was collected from the natural Scyllibacus orientalis Desjardins, 1831 inlet of the outer channel i.e. Shipakuda region (19°39'54.51"N & 85°29'13.41"E) of Chilika lagoon The details of morphometric features of two adjoining the Bay of Bengal and second specimen specimens of flat head lobster can be viewed from was caught at Magarmukh area (19°41'48.14"N & Table 1. Body was strongly depressed; cephalothorax 85°24'47.96"E). After collection the meaturements flattened; triangular narrowing posterior; cervical were taken in live condition and then preserved in incision two on lateral margin of the carapace; teeth 10% formalin solution (collection date: 23rd March on the lateral margin of the carapace absent apart 2009; voucher no. 3/lobster/23.3.2009/OC). Specimens from the anterolateral and post cervical. Orbits on the were photographed before preservation (Fig. 2 A&B). anterolateral angle of the carapace; exopod of third The observed specimens followed the following and first maxilliped without a flagellum. Eyes placed systematic positions. at the anterolateral corners of carapace. The specimen collected is identified as Thenus orientalis Lund, Phylum: 1793 (Table 1; Fig. 2). Class: Mostly Indo-Pacific10. Native to the western Order: Decapoda and eastern region of the Indian Ocean, northwest, 1890 INDIAN J. MAR. SCI., VOL. 47, NO. 09, SEPTEMBER 2018

Fig. 2 — Image showing dorsal side of Thenus orientalis (A), ventral side (B) collection from Shipakuda region (large sized ) and Magarmukh region ( small sized)

Table 1 — Morphometric characteristics of the flat head lobster Thenus orientalis from Shipakuda region (specimen 1) and Magarmukh region (specimen 2) of Chilika lagoon. Sl.no. Morphometric characters Specimen 1 (Shipakuda) Specimen 2 (Magarmukh) 1 Total length 16.2 12.1 2 Total width 5.5 4.6 3 Length of the Antenna 3.2 2.4 4 Eye diameter 0.4 0.2 5 Eye peduncle 0.5 0.1 6 Length of maxila 2 1.5 7 Carapace length 6.1 4.4 8 Carapace width 7.7 5.8 9 Pereopods (Walking legs) 5 pairs 5 pairs Length of 1st leg 4.5 4 Length of 2nd leg 5.2 4.5 Length of 3rd leg 5.2 4.5 Length of 4th leg 5.2 4.3 Length of 5th leg 5 3.8 10 Pleopods (swimming legs) 5 pairs 5 pairs Length of 1st leg 1.5 1.1 Length of 2nd leg 1.5 1.1 Length of 3rd leg 1.5 1.1 Length of 4th leg 1.5 1.1 Length of 5th leg 1.2 0.8 11 Abdomen length 4.6 3.7 12 Abdomen width 4 3.3 13 Tail length 0.7 0.5 14 Tail width 2.6 2.1 15 Length of left 1st uropod 2.3 2.1 16 Length of left 2nd uropod 2.1 1.8 17 Length of right 1st uropod 2.3 2.1 18 Length of right 2nd uropod 2.1 1.8 19 Telson length 1.6 1.1 20 Telson width 2.5 2

MAHAPATRO et al.: First RECORD OF A FLATHEAD LOBSTER FROM CHILIKA LAGOON 1891

western and central Pacific. southern Red Sea, This is the first time ever to record a species of Arabian Gulf, Gulf of Thailand, Vietnam, Indonesia, Thenus from shallow brackish water region like outer Philippines and southern Japan and coasts of channel area of Chilika lagoon which is well Bay of Bengal. connected to the Bay of Bengal with a couple of The flat head lobster Thenus orientalis differs from lagoon inlets. It is likely that T. orientalis might have T. unimaculatus in having small brown spots on the entered into the lagoon waters either due to the tidal pereopods. T. unimaculatus bears purple-blotched incursion or in search of preferred food materials. pereopods while the pereopod of T. indicus devoid of Usually the food of T. orientalis comprises benthic spots. In the present study, the species collected from invertebrates such as gastropods, bivalves, , Magarmukh region (19°41'48.14"N & 85°24'47.96"E) and small fishes with a preference for bivalves, was found small in size while the larger specimen is clams, mussels and oysters13. These are the benthic collected from the Shipakuda region (19°39'54.51"N dwellers commonly abundant for feeding in the outer & 85°29'13.41"E) of Chilika lagoon. Observation of channel area of Chilika14. Interestingly, Chilika this lobster species obviously increases the lagoon has a large shell bank in front of the lagoonal diversity of Chilika lagoon particularly after the inlet supporting an expanse of dead and live bivalves artificial opening of the new mouth. such as Crassostrea cuttackensis, Meretrix meretrix, gastropods Cerithideopsilla cingulata, Telescopium Discussion telescopium and Turbo sp. The diversity of this The distribution of Thenus species is determined by marine influenced region of Chilika lake is as good as the accessibility of suitable habitat and preferred food any of the coastal ecosystem of the world. The large availability. Habitat depth ranges from shallow to shell bank colonies can also responsible for providing about 20 m in the muddy inshore region favored by shelter. Again, the observed specimen measures more T. parindicus while T. australiensis prefers rocky than 16 cm and 12 cm only; it could possibly attain a areas3,4. T. indicus, reported from Thailand water maximum body length of 25 cm with a carapace favors shallow waters compared to T. orientalis. The 15 length of 8 cm . Thus, observed specimen may be habitat of T. orientalis is indicative of a preference for considered as a young one. Nonetheless, the a medium range of sediments rather than fine conservation status of T. orientalis has been assessed sediment11. The morphological differentiation of the as ‘least concern’ by IUCN because of its global three species Thenus revealed that T. indicus and 10 distribution . T. orientalis have a number of dark brown spots over the carapace whereas in T. unimaculatus purple spots Conclusion are sharply visible. The significant feature associated The significance of Chilika lagoon as a rich source with the carapace of T. orientalis is the occurrence of of food14 for a wide range of organisms; cannot be pink spots and pink blotches near the orbits. overlooked. The occurrence of T. orientalis in such Pereopods of T. orientalis are peculiarly spotted while shallow water region could be partly attributable to T. unimaculatus is characterized with a purple blotch this while the influence of physical, environmental on the inner face of the merus of 1 or more 5 conditions and biological interactions determine the pereopods . The genus Thenus has five species such large scale distribution of Thenus sp. Globally, the as T. indicus Leach, 1815, T. orientalis Lund, 1793, 5 Thenus, population is under severe threat due to T. australiensis , T. unimaculatus Burton and Davie, over exploitation and incidental catch. However, 20075 and T. parindicus. 5 appropriate aquaculture strategies can facilitate in Burton and Davie concluded that despite sustaining their population particularly the long-lived significant genetic divergence, several sympatric larvae against a backdrop of ecological disturbances. species are morphologically similar and identification As a first documentation of Thenus orientalis from could be difficult. In addition, Thenus orientalis was Chilika lagoon should provide scope towards baseline considered as the only predominant species found in 12 conservation strategies. the Indian subcontinent . It is ascertained as T. unimaculatus Burton and Davie, 2007. However, Acknowledgment the specimen collected during this study is The authors are thankful to the Head, Department morphologically similar to that of Thenus orientalis as of Marine Sciences, Berhampur University, compared to T. unimaculatus. Chief Executive, Chilika Development Authority, 1892 INDIAN J. MAR. SCI., VOL. 47, NO. 09, SEPTEMBER 2018

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