On the record of herring bow crab Varuna litterata (Fabricius, 1798) from Cochin Backwaters, India

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1 Indian Journal of Geo Marine Science Vol.46 (05), May 2017, pp On the record of herring bow crab Varuna litterata (Fabricius, 1798) from Cochin Backwaters, India P. Lakshmi Devi & *Aneykutty Joseph Dept. of Marine Biology, Microbiology and Biochemistry, School of Marine Sciences, Cochin University of Science and Technology, Fine Arts Avenue, Cochin , India. *[ Received 05 February 2014 ; revised 19 December 2014 Present study is on the record of occurrence of the herring bow crab, Varuna litterata from Cochin Backwaters. Study reveals that V. litterata occur in the Cochin Backwaters plentifully throughout the year and are found to be an inhabitant of mangrove regions and prefer areas with close proximity to the sea having good tidal influx. [Key words: Varuna litterata, Cochin Backwaters, Morphology, Habitat] Introduction Varuna litterata, is a grapsid crab, are euryhaline and can be found in rivers, brackish waters or at sea. After a flood, it can be washed far away in the sea and observed there drifting with pieces of debris 1. They are found to prefer areas faced to more oceanic waters 2. One of the first studies on V. litterata is by Kemp (1915) 3, who reported the mass migration of the megalopae in the Hooghly River near Calcutta, India. A Similar phenomenon was observed in Fiji in Panikker (1951) 5 and Gross et al. (1996) 6 dealt with the osmoregulation in V. litterata and proved that they show strong osmoregulation even in 150% seawater. The metabolic effect of eyestalk removal in V. litterata was studied by Madhyastha and Rangneker (1974) 7. Behavioral study of V. litterata in the coastal waters of Bay of Bengal was carried out by Manna (1988) 8. Tu Chin-Hung (1992) 9 documented the whole zoeal development of V.litterata. Jameieson et al. (1996) 10 analysed the spermatozoa ultrastrucure of V. litterata. V. litterata has been reported from all over the Indo-West Pacific In India, it is found to be very abundant in the Sunderbans of West Bengal, estuarine regions of Hoogly and in Gulf of Mannar and Palk Bay 17,18. In the West coast of India, V. litterata was first collected by Pillai (1951) 19 from the open sea at Trivandrum, but not reported from the Travancore backwaters. Later Chhapgar (1957) 20 reported V.litterata from Bombay and Kolak. The species was found to occur in the waters along the Karnataka coast by Dineshbabu et al. (2011) 21. A comparative study on the brachyuran biodiversity of three brackishwater lakes, viz. Chilka Lake, Pulicut Lake and Vembanad Lake 22 revealed that they are present in Pulicut and Chilka Lake but are found to be absent in Vembanad Lake. Hence, the present work is the first report on the occurrence of V. litterata in Cochin Backwaters and the study also deals with the morphology and the habitat preferred by V. litterata Materials and Methods As a part of the survey conducted to find the diversity of brachyuran crabs, 15 sampling stations were selected along the study area, Cochin backwaters, which is located at the northern tip of Vembanad Lake (Fig.1). Sampling was conducted on a monthly for a period of two years from June 2010 to May 2012, for the collection of crab specimens and the study of hydrographical parameters.

Carapace of the crab is squarish, with a smooth surface and the groove separating the gastric and the cardiac regions is well demarcated. Colour of the carapace is light brown to brownish grey.

2 996 INDIAN J. MAR. SCI., VOL. 46, NO. 05, MAY 2017 in large numbers from the Cochin backwaters in stake nets and Chinese dip nets. Among the 15 stations, V. litterata is found to be available only in 4 stations, hence the ecological parameters of these stations were analysed, inorder to figure out the habitat type preferred by the species. Carapace of the crab is squarish, with a smooth surface and the groove separating the gastric and the cardiac regions is well demarcated. Colour of the carapace is light brown to brownish grey. Anterolateral borders of the carapace is cut into three broad, but less sharp teeth and the lateral borders are convergent backwards (Plate 1). Fig. 1. Map showing the study area Cochin Backwaters, with the sampling stations The crab specimens collected are then brought to the lab alive and its colour, carapace width, carapace length, and the morphological features like shape of the carapace, markings on the body, number of anterolateral teeth, features of frontal lobe, pubescence, spination on the chelae and other legs are noted. It is then numbed by freezing and preserved in 10% formaldehyde for further identification. The collected specimens are then identified up to species level using standard methods 13,20,23. The first male pleopod and the third maxillipeds act as an important taxonomic tool 20,24. These structures are carefully dissected out and studied under a binocular microscope. These are then described and drawn with the help of a camera lucida. Standard techniques were employed for the analysis of water quality parameters viz. temperature (centigrade thermometer), salinity (salinorefractometer), ph (digital ph meter) and the sediment quality parameters, viz. Organic carbon content (Walkley-Black method) 25 and the sediment texture (Particle Size Analyzer., Sympatec Germany) Results A two years survey conducted along the 15 selected stations of Cochin backwaters revealed the occurrence of V.litterata plentifully in the backwaters throughout the year. They are caught Plate 1. Photograph showing the dorsal view of V. litterata Plate 2. Photograph showing the postero-lateral facets of the carapace The postero-lateral facets are well-defined (Plate 2). Dactylus, propodus and carpus of legs are laterally flattened like paddles and are fringed with long, densely packed hairs (Plate 3). With its legs shaped as paddles used for swimming, it is sometimes called the Paddler crab.

DEVI & JOSEPH: ON THE RECORD OF CRAB VARUNA LITTERATA FROM COCHIN BACKWATERS 997 Plate 3.

However, sexual dimorphic characters are similar to that of other crabs.

and changes to semi circular in adults (Plate 5). Though chelipeds are symmetrical in both sexes, males have relatively larger chelae than females (Plate 6). Plate 6.

litterata Males have pleopods modified as copulatory organs and they are observed to be stout and have uniform width throughout the length (Fig. 2).

3 DEVI & JOSEPH: ON THE RECORD OF CRAB VARUNA LITTERATA FROM COCHIN BACKWATERS 997 Plate 3. Photograph showing the paddle shaped legs Sexes cannot be differentiated from their colour patterns of the dorsal exoskeleton. However, sexual dimorphic characters are similar to that of other crabs. Sex is readily distinguished in sexually mature individuals by the shape of the abdomen which is narrow and T shaped in males (Plate 4) while in females, it is triangular in juveniles and changes to semi circular in adults (Plate 5). Though chelipeds are symmetrical in both sexes, males have relatively larger chelae than females (Plate 6). Plate 6. Photograph showing the chelipeds of male and female V. litterata Males have pleopods modified as copulatory organs and they are observed to be stout and have uniform width throughout the length (Fig. 2). Tips are rounded and are fringed with hairs. The third maxilliped have a thick exopod, which is wider than the ischium (Fig 3). Fig. 2. Camera lucida drawing of 1 st pleopod of male V. litterata Plate 4. Photograph showing the male abdomen of V. litterata Fig. 3. Third maxilliped of V. litterata Plate 5. Photograph showing the female abdomen of V. litterata Habitat Preference: Among the 15 stations surveyed, V. litterata was found to occur only in 4 stations namely, Kandakkadavu, Kumbalanghi, Vypin and Munambam (Fig.1-higlited with arrow marks). A detailed study was then conducted on the location type, habitat and the physico-

4 998 INDIAN J. MAR. SCI., VOL. 46, NO. 05, MAY 2017 chemical parameters of these four stations, to draw an inference on the habitat type preferred by the species. Kandakkadavu (station 1), which lies at the west part of the backwaters is a typical coastal area ornamented with lush green mangroves. Kumbalanghi (station 2) is a fishing village, and has a very vast backwater stretch, Here; the backwater is in an enclosed condition with a rather narrow opening into the backwaters. This site too has a rich diversity of mangroves and mangrove associates. Vypin (station 3) is the biggest among the group of island in the Cochin backwaters and is bound by Arabian Sea on its western side and the backwaters on its eastern side. The station is ornamented with luxuriant mangrove patches earlier. Munambam (station 4) is a coastal village, situated at the Northern point of the backwaters, surrounded by Arabian Sea on the West, Periyar on the East and a mouth opening to the sea on the North. The site does not have luxuriant mangrove vegetation, only a sparse patch is found. The analysis of water and sediment quality parameters reveals that, in general, a wide fluctuation prevails in the case of salinity and temperature during the study period. The stations exhibited a low salinity (1-6 ppt) during the monsoon season, while it increased during the post monsoon and pre monsoon period. Highest salinity was observed during the pre monsoon period (22-31 ppt). Temperature too showed a wide fluctuation. During the monsoon months, temperature was comparatively lower ( C). ph was almost neutral in the four stations throughout the study period. Sediment texture analysis showed that all the four stations are sandy in nature and the sediment also exhibited a higher amount of organic carbon content owing to the litter fall from the mangroves. The study reveals that V. litterata inhabits the mangrove regions, characterized with sandy substratum and rich in organic carbon content and they are found to prefer areas with close proximity to the sea having good tidal influx. Discussion The present study is the first record of V. litterata from Cochin Backwaters, Kerala, South India. One of the first studies on V. litterata is by Kemp (1915) 3 who observed its occurrence in the Gangetic delta in abundance. He also observed the presence of megalops of V. litterata in the Hughly River, in the vicinity of Kolkata during monsoon. In the East coast of India, it is found to be very abundant in the Sunderbans of Bengal, estuarine regions of Hoogly and in Gulf of Mannar and Palk Bay 18. Roy and Nandi (2008) 22 reported its occurrence in Chilka and Pulicat lake. In the West coast of India, V. litterata was first collected by Pillai (1951) 19 from the open sea at Trivandrum, but not reported from the Travancore backwaters. Later Chhapgar (1957) 20 reported V.litterata from Bombay and Kolak. The species was found to occur in the waters along the Karnataka coast by Dineshbabu et al. (2011) 21. V.litterata is found to occur only in four stations among the 15 stations surveyed, namely Kandakkadavu, Kumbalanghi, Vypin and Munambam. When the habitat ecology was analysed, these four stations exhibited a sandy substratum with high organic carbon content and good tidal influx due to more proximity to the sea. The higher amount of organic carbon in the sediments can be attributed to the litter fall from mangroves. V. litterata inhabit mangrove regions 26 and prefer areas faced by more tidal water 2, which is in complete agreement with the findings of the present study. Hence, the work concluded that V. litterata is an inhabitant of mangrove regions with sandy substratum, rich in organic carbon and prefer areas with close proximity to the sea having good tidal influx. A comparative study on the brachyuran biodiversity of three brackishwaters lakes, viz. Chilka Lake, Pulicut Lake and Vembanad Lake 22 reported that they are present in Pulicut and Chilka Lake and do not occur in Vembanad Lake. Hence the present work revealed that V.litterata is found to be available plentifully in the Cochin backwaters, which is situated at the northern tip of Vembanad Lake and is the first report on the occurrence of V. litterata from Cochin Backwaters. Conclusion The study reports the presence of the herring bow crab, V.litterata in the Cochin backwaters for the first time, which was earlier reported to be absent. They occur plentifully in the mangrove regions and prefer areas with close proximity to the sea having good tidal influx. Acknowledgements The first author is thankful to Kerala State Council for Science, Technology and Environment, Sastra Bhavan, Pattom, Trivandrum, Kerala, India for the KSCSTE Research Fellowship. Authors are thankful to Dept. of Marine Biology, Microbiology & Biochemistry, School of Marine Sciences, Cochin University of Science & Technology for providing the necessary facilities to carry out this work.

5 DEVI & JOSEPH: ON THE RECORD OF CRAB VARUNA LITTERATA FROM COCHIN BACKWATERS 999 References 1. Bouchard, J., Poupin, J., Cleva, R., Dumas, J. & Dinhut, V., Land, mangrove and freshwater decapod crustaceans of Mayotte region (Crustacea :Decapoda), Atoll Research Bulletin, No.XXX, (2011) mmary.php?id= Kemp, S. W., Fauna of the Chilka lake. Crustacea Decapoda, Indian Museum, 5 (1915): Ryan, P. A &. Choy, S. C., Observations on the upstream migration of Varuna litterata (Fabricius) megalopae (Decapoda, Brachyura, Grapsidae) in Fiji. Crustaceana, 58(3) (1990): Panikker, N. K., Physiological aspects of adaptations to estuarine conditions. Proc. Indo-Pacific Fish. Council, 2 nd meeting, 17 th to 18 th April 1950, Cronulla, N.S.W. Australia, Sect.3 (1951): Gross, W., Robert, J., Lasiewski, C., Dennis, M. & Paul R., Jr., Salt and water balance in selected crabs of Madagascar. Comparative Biochemistry and Physiology, 17(2) (1996): Madhyastha, M. N. & Rangneker, P. V., Metabolic effects of eyestalk removal in the crab Varuna litterata (Fabricius). Hydrobiologia, 48(1) (1974): Manna, A. K., Behavioural study on a small edible crab Varuna litterata in the coastal water of Bay of Bengal. Environment and Ecology, 6(3) (1988): Tu, Ching-Hung., Studies on the larval culture of Varuna litterata. Master s Thesis, Institute of Marine Biology, National Sun Yat-Sen University, Kaohsiung, Taiwan, (1992). 10. Jamieson, B. G. M., Guinot, D. & Richer De Forges, B., Contrasting spermazoal ultrastructure in two thoracotreme crabs, Cardisoma carnifex (Gercarcinidae) and Varuna litterata (Grapsidae) (Crustacea, Brachyura). Invertebr. Reprod. Dev, 29 (1996): Alcock, A., The Brachyura Catometopa oe Grapsoidea : Materaials for a carcinological fauna of India, No.6. Journal of Asiatic society of Bengal, 69(3) (1900): Sakai, T., Studies on the crabs of Japan.IV. Brachygnatha, Brachyryncha. Yokendo, Tokyo, (1939): , pls Sakai, T., Crabs of Japan and the Adjacent Seas. (Kodansha, Tokyo), (1976): Pp I-XXIX, 1-773, 3 maps (English volume); pp 1-16, pls (plates volume); pp (Japanese Volume). 14. Barnard, K. H., Descriptive catalogue of South African Decapod Crustacea (Crabs and shrimps). Annuals of South African Museum, 38 (1950): 1-837, figs Crosnier, A., Crustaces Decapodes Grapsidae Faune de Madagascar, 18 (1965): 1-143, figs 1-260, pls Holthius, L. B., A collection of decapods crustacean from Sumba, Lesser Sunda Islands, Indonesia. Zoologische Verhandelingen, 162 (1978): Hora, S. L., A note on the bionomics of two estuarine crabs. Proc. Zool.Soc.London, (1933): , pls i-ii. 18. Rao, P. V., Thomas, M. M. & Rao, S., The crab fishery resources of India. Proc.Symp.Living resources of the seas around India, (1973): Pillai, N. K., Decapoda (Brachyura) from Travancore. Bull. Cent. Res. Inst. Univ. of Travancore, 1951, Trivandrum, 2(1) (1951): Chhapgar, B. F., Marine crabs of Bombay State. Contribution No.1, (Taraporevala, Marine Biological station) (1957). 21. Dineshbabu, A. P., Durgekar, R. N. & Zacharia, P. U., Estuarine and Marine decapods of Karnataka-inventory. Fishing chimes,vol.30, No.10 & 11 (2011): Roy, M. K. D. & Nandi, N. C., Brachyuran biodiversity of some selected brackish water lakes of India. Proceedings of Taal 2007 : The 12 th World Lake Conference, (2008): The Marine Species Identification Portal. URL: Ajmal Khan, S. & Ravichandran, S., Brachyuran crabs. In: UNU-INWEH-UNESCO International training course on coastal biodiversity in marine ecosystems edited by K. Kathiresan & S. Ajmal Khan (Annamalai University, CAS in Marine Biology, Parangipettai) 2008, pp Jackson, M. L., Soil chemical Analysis (Printice-Hill of India Private Limited, New Delhi)

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