Crab Biodiversity from Arukkattuthurai to Pasipattinam, South East Coast of India

676Indian Journal of Geo-Marine Sciences INDIAN J MAR SCI VOL 43(4), APRIL 2014 Vol. 43(4), April 2014, pp. 676-698

Crab biodiversity from Arukkattuthurai to Pasipattinam, south east coast of India

D. Varadharajan & P. Soundarapandian Faculty of Marine Sciences, Centre of Advanced Study in Marine Biology, Annamalai University, Parangipettai-608 502, Tamil Nadu, India. [E-Mail: [email protected]] Received 30 July 2012; revised 14 January 2013

Coastal environment provides a greater range of habitats and thus potentially supports greater biodiversity. Before starting to produce seeds in a hatchery and culture them in ponds, thorough knowledge about their distribution in nature is important. So the present study is aimed to know the biodiversity of crabs from Arukkattuthurai to Pasipattinam. Totally 79 individual crab species were recorded belonging to 21 families from all 10 stations. Maximum crab species were recorded belonging to the family Portunidae than others families and also the maximum number of crab species 163 were recorded in Mallipattinam (station5) and minimum 69 species in Pasipattinam (station10). Occurrence of crab species in different stations were in the following order; Mallipattinam (163) > Sethubavachatram (161) > Manamelkudi (127) > Pointcalimere (117) > Muthupettai (116) > Jegathapattinam (110) > Kattumavadi (101) > Arukkattuthurai (92) > Adirampattinam (85) > Pasipattinam (69). Crabs were collected plenty during summer and monsoon than pre-monsoon and post-monsoon. The crabs belonging to families viz., Calappidae, Portunidae, Potamidae, Grapsidae, Sesarmidae and Ocypodidae were obtained almost all seasons.

[Keywords: Crabs, Family, Portunidae, Distribution, Abundance]

Introduction introduction are identified as main threat to 9 Biodiversity is important for human survival and biodiversity . India, a mega biodiversity country, economic interests and for the environmental purpose definitely needs conservation strategy to save the and stability. India’s marine and coastal ecosystems biodiversity. Although, the crabs are caught constitute an important natural resource, since throughout the year at various regions of the coast, millions of people dependent on them for their the main season varies from place to place10. In the livelihoods. This rich biodiversity has a significant present study an attempt has been made on the role in the maintenance of the ecosystem. Crustaceans biodiversity of crabs from Arukkattuthurai to are visibly a remarkable group of organisms with a Pasipattinam south east coast of India. long evolutionary history and prominent adaptability. Materials and Methods The decapod crabs are mostly active animals with complex behaviour patterns. Southern coast of Tamil The present study was carried out for one year Nadu has a very narrow continental shelf, with high from January 2010 to December 2010 from salinity, a rocky shore and strong wave action. It Arukkattuthurai to Pasipattinam, south east coast of includes mangroves, sandy beaches, mudflats, coral India. Ten different stations were selected for the reefs and seagrass beds1,2. Detailed study on decapod present study viz., Arukkattuthurai (Station1), crab fauna was already made in Indian seas by Pointcalimere (or) Kodikkarai (Station2), Muthupettai different workers3,4,5,6,7,8. Habitat destruction, (Station3), Adirampattinam (Station4), Mallipattinam pollution, over exploitation and new species (Station5), Sethubavachatram (Station6), VARADHARAJAN & DARAPANDIAN: CRAB BIODIVERSITY FROM ARUKKATTUTHURAI TO PASIPATTINAM 677

Kattumavadi (Station7), Manamelkudi (Station8), Jegathapattinam (Station9) and Pasipattinam (Station10). Crabs were collected by using FRB boats in different depths (up to 25 m) and 40–50 mm net was used (Length 80–100 m, Breadth 1.0-1.5 m). Apart from collection a regular visit was made in different fishing sites, landing centres and sell points. The number of crabs that belonging to different species were recorded and identified up to species level using the taxonomic keys of 11,12,13,14. Results In the present study totally 79 crab species were recorded belonging to 21 families. Family Aethridae was represented by single genera consists (Cryptopodia) of a species C. fornicata. Family Calappidae was represented by 2 genera (Calappa and Matuta) consists of 4 species which includes

C. lophos (Plate1a1), C. gallus (Plate1a2), M. lunaris

(Plate1a3) and M. planipes (Plate1a4). Family Carpillidae was represented by a genera (Carpilius)

consists of a species C. maculates (Plate1a5). Family Dorippidae was represented by 3 genera (Dorippoides, Dorippe and Ethusa) consists of 3

species which includes D. facchino (Plate1a6),

D. quadridens (Plate1a7) and E. indica. The family Leucosiidae was represented by two genera (Oreophorus and Arcania) consists of 2 species which includes O. reticulates and A. septemspinosa

(Plate1a8). The family Hymenosomatidae was represented by only one genera (Elamena) consists of a species E. cristatipes. Family Majidae was represented by 3 genera (Hyastenus, Doclea and Achaeus) consists of 3 species which includes H. gracilirostris, D. gracilipes and A. lacertosus. The family Parthenopidae was represented by 2 genera (Parthenope and Platylambrus) consists of 2 species which includes P. echinatus and P. prensor. The family Pilumnidae was represented by only one genera 678 INDIAN J MAR SCI VOL 43(4), APRIL 2014

(Pilumnopeus) consists of a species P. vespertilio The family Xanthidae was represented by 4 genera

(Plate1a9). Family Portunidae was represented by 5 (Paractaea, Leptodius, Zozymodes and Demania) genera (Scylla, Portunus, Podophthalmus, Charybdis consists of 4 species which includes P. neospeciosa, and Thalamita) consists of 24 species which includes L. exaratus, Z. cavipes and D. buccalipes. The family

Scylla tranquebarica (Plate1a10), S.serrata (Plate1a11), Oziidae was represented by only one genera (Ozius)

Portunus sanguinolentus (Plate1a12), P. pelagicus consists of a species O. rugulosus. The family

(Plate1a13), P.gladiator (Plate1a14), P. hastatoides Grapsidae was represented by 7 genera (Grapsus,

(Plate1a15), P.trituberculatus (Plate1a16), Metopograpsus, Metaplax, Leucosia, Philyra, Dromia and Plagusia) consists of 9 species which includes Podophthalmus vigil (Plate1a17), C.affinis (Plate1a18), Grapsus albolineatus, G. strigosus, M. messor, C.feriata (Plate1a19), C.natator (Plate1a20), M. maculatus, M. distincta, L. pubescens, P. globosa, C. (Goniosoma) lucifera (Plate1a21), C. (Goniohellenus) D. dormia and P. depressa tuberculata. The family truncata (Plate1a22), C. hellerii (Plate1a23), Sesarmidae represented by 2 genera (Sesarma and C. granulata (Plate1a24), C. rostrata, C. japonica, C. miles, C. variegata, C.hoplites, T. picta ,T. chaptali, Nanosesarma) consists of 5 species which includes T. crenata and T. sima. The family Potamidae was S.brockii, S. (Chiromantes) bidens, S. (Parasesarma) represented by 3 genera (Sartoriana, Spiralotelphusa plicatum, S. tetragonum and N. batavicum. Family and Potamon) consists of 3 species which includes Ocypodiae was represented by 3 genera (Uca, S. spinigera, S. hyhrodroma and P. fluviatile. The Ocypoda and Dotilla) consists of 6 species which family Trapeziidae was represented by only one includes U. annulipes, U.lactea, U.vocans, genera (Trapezia) consists of a species of T. cymodoce. O. platytarsis, O. macrocera and D.myctiroides. Family Macrophthalmidae was represented by only one genera (Macrophthalmus) consists of 2 species which includes M. convexus and M. depressus. The family Gecarcinidae was represented by only one genera (Cardisoma) consists of a species C. carnifex. Family Diogenidae was represented by 2 genera (Clibanarius and Dardanus) consists of 4 species which includes C. longitarsus, C. arethusa, C. olivaceus and D. megistos. Family Paguridae was represented by only one genera (Spiropagurus) consist of a species S. spirifer (Table 1). Maximum crab species recorded in the present study was belonging to the family Portunidae than others families and also the maximum 79 species were recorded in Mallipattinam (station5) and minimum 42 species in Pasipattinam (station10). The occurrence of crab species in different stations were in the following order; Mallipattinam (163) > Sethubavachatram (161) > Manamelkudi (127) > Pointcalimere (117) > Muthupettai (116) > Jegathapattinam (110) > Kattumavadi (101)> Arukkattuthurai (92) > Adirampattinam (85)> Pasipattinam (69) (Table 1). In the present study maximum crabs were collected during summer and monsoon than pre-monsoon and post-monsoon. The VARADHARAJAN & DARAPANDIAN: CRAB BIODIVERSITY FROM ARUKKATTUTHURAI TO PASIPATTINAM 679

Table 1—Checklist of crab species recorded during the study in different stations S. No Species Stations & (No/m2) Family 12345678910 1 Cryptopodia fornicate (Fabricius, 1781) Aethridae ++++++++++ 2 Calappa lophos (Herbst, 1782) Calappidae ++++++++++ 3 C. gallus (Herbst, 1803) ++++++++++ 4 Matuta lunaris (Forskal, 1775) ++++++++++ 5 M.planipes (Fabricius, 1798) + + * +++++** 6 Carpilius maculatus (Linnaeus, 1758) Carpillidae ++++++++++ 7 Dorippoides facchino (Herbst, 1785) Dorippidae ++++++++++ 8 Dorippe quadridens (Fabricius, 1793) ++++++++++ 9 Ethusa indica (Alcock,1894) * + * * + + * + * * 10 Oreophorus reticulatus (Adams & White, 1849 ) Leucosiidae * + * * + + * + * * 11 Arcania septemspinosa (Fabricius, 1787) ++++++++++ 12 Elamena cristatipes (Gravely, 1927) Hymenosoma-tidae ++++++++++ 13 Hyastenus gracilirostris (Miers, 1879) Majidae ++++++++++ 14 Doclea gracilipes (Stimpson,1857) ++++++++++ 15 Achaeus lacertosus (Stimpson, 1858) +++++++*++ 16 Parthenope echinatus (Herbst, 1790) Parthenopidae ++++++++++ 17 Platylambrus prensor (Herbst, 1803) ++++++++++ 18 Pilumnus vespertillio (De Man, 1887) Pilumnidae ****+++++* 19 Scylla tranquebarica (Fabricius, 1798) Portunidae ++++++++++ 20 S. serrata (Forskal, 1775) ++++++++++ 21 Portunus sanguinolentus (Herbst, 1783) ++++++++++ 22 P. pelagicus (Linnaeus, 1758) ++++++++++ 23 P. gladiator (Fabricius, 1798) ++++++++++ 24 P. hastatoides (Fabricius, 1798) ** +++++*** 25 P. trituberculatus (Miers, 1876) +++++++++* 26 Podophthalmus vigil (Fabricius, 1798) * +++++++++ 27 Charybdis affinis (Milne Edwards,1861) *** +++++** 28 C. feriata (Linnaeus, 1758) ++++++++++ 29 C. natator (Herbst, 1794) ++++++++++ 30 C. (Goniosoma) lucifera (Fabricius,1798) *** +++++** 31 C. (Goniohellenus) truncata (Fabricius, 1798) ++++++++++ 32 C. hellerii (A. Milne Edwards, 1867) ++++++++++ 33 C. granulata (De Haan, 1835) ++++++++++ 34 C. (Goniosoma) rostrata (A. Milne Edwards,1861) * +++++++** 35 C. japonica (A. Milne Edwards, 1861) +++++++*** 36 C. miles (De Haan, 1835) ++++++++++ 37 C. variegata (Fabricius, 1798) +++++++++* 38 C. (Goniohellenus) hoplites (Wood Mason,1877) ++++++++++ 39 Thalamita picta (Stimpson, 1858) ++++++++++ 680 INDIAN J MAR SCI VOL 43(4), APRIL 2014

40 T. chaptali (Audouin, 1826) * ++++++*** 41 T. crenata (Ruppell, 1830) ++++++++++ 42 T. sima (Milne Edwards,1834) ++++++++++ 43 Sartoriana spinigera (Wood Manson,1871) Potamidae * + * ++++++* 44 Spiralotelphusa hyhrodroma (Herbst,1794) ++++++++++ 45 Potamon fluviatile (Herbst, 1785) ++++++++++ 46 Trapezia cymodoce (Herbst, 1801) Trapeziidae * ++++++*** 47 Paractaea neospeciosa (Deb, 1989) Xanthidae * +++++++++ 48 Leptodius exaratus ( H. Milne Edwards, 1834) ++++++++++ 49 Zozymodes cavipes (Dana, 1852) * + * * + * + * + * 50 Demania buccalipes (Alcock, 1898) * + * * + + * + * * 51 Ozius rugulosus ( Stimpson, 1858) Oziidae * + * * + + * * * * 52 Grapsus albolineatus ( Lamarck, 1818) Grapsidae ++++++++++ 53 G.strigosus (Herbst, 1799) +++++++++* 54 Metopograpsus messor (Forskal, 1775) * +++++++*+ 55 M.maculatus (Milne-Edwards, 1853) + + * ++++++* 56 Metaplax distincta (H. Milne Edwards, 1852) * + * + + + * + + * 57 Leucosia pubescens (Miers, 1877) + + * +++++++ 58 Philyra globosa (De Man, 1888) ++++++**** 59 Dromia dormia (Linnaeus, 1763) +++++++++* 60 Plagusia depressa tuberculata (Lamarck, 1818) ++++++++++ 61 Sesarma brockii ( De Man, 1887) Sesarmidae ++++++++++ 62 S. (Chiromantes) bidens (De Haan, 1835) ++++++*++* 63 S. (Parasesarma) plicatum (Latreille, 1806) ++++++++++ 64 S. tetragonum (Fabricius, 1798) + + * +++++++ 65 Nanosesarma batavicum (Moreira, 1903) ++++++++++ 66 Uca annulipes ( H. Milne Edwards, 1937 ) Ocypodidae ++++++++++ 67 U. lactea (De Haan, 1835) ++++++*+++ 68 U. vocans (Linnaeus, 1758) ++++++++++ 69 Ocypode ceratophthalmus (H. Milne-Edwards,1852) * + * + + + * + * * 70 O. macrocera ( H. Milne-Edwards, 1852) ++++++++++ 71 Dotilla myctiroides (H. Milne Edwards, 1852) ++++++++++ 72 Macrophthalmus convexus (Stimpson, 1858) Macrophthal-midae ++++++++++ 73 M. depressus *+*+++*+** 74 Cardisoma carnifex (Herbst, 1796) Gecarcinidae ++++++++++ 75 Clibanarius longitarsus (De Haan, 1849) Diogenidae ++++++++++ 76 C. arethusa (De Man, 1888) ****++*+++ 77 C. olivaceus (Henderson, 1915) * +++++++++ 78 Dardanus megistos (Herbst, 1804) ****+++++* 79 Spiropagurus spirifer (Stimpson, 1858) Paguridae +++++++++* Total 92 117 85 116 163 161 101 127110 69 (+present and *absent) [Arukkattuthurai (1), Pointcalimere (2), Muthupettai (3), Adirampattinam (4), Mallipattinam (5), Sethubavachatram (6), Kattumavadi (7), Manamelkudi (8), Jegathapattinam (9) and Pasipattinam (10) ]. VARADHARAJAN & DARAPANDIAN: CRAB BIODIVERSITY FROM ARUKKATTUTHURAI TO PASIPATTINAM 681 crabs belonging to the families viz., Calappidae, and minimum in Pasipattinam (5.5036). Margalef’s Portunidae, Potamidae, Grapsidae, Sesarmidae and diversity index was maximum in Mallipattinam Ocypodidae were obtained almost all the seasons (5.1218) and minimum in Pasipattinam (4.412). (Table 2). Margalef’s species richness was maximum in The pielou’s evenness of crabs was maximum in Adirampattinam (14.0946) and minimum in Pointcalimere (0.9775) and minimum in Pasipattinam (11.5776). Simpson index was Jegathapattinam (0.9531). Shannon Wienners maximum in Pointcalimere (0.9816) and minimum diversity was maximum in Mallipattinam (5.9008) in Muthupettai (0.9741) (Table 3).

Table 2—Abundance of crabs in different seasons. S.No Family Postmonsoon Summer Premonsoon Monsoon 1 Aethridae - + + + 2 Calappidae + + + + 3 Carpillidae - + + + 4 Dorippidae + + - + 5 Leucosiidae + - - + 6 Hymenosomatidae - - + + 7 Majidae + + - + 8 Parthenopidae - - + + 9 Pilumnidae + + - - 10 Portunidae + + + + 11 Potamidae + + + + 12 Trapeziidae - + - + 13 Xanthidae - + + + 14 Oziidae + - - + 15 Grapsidae + + + + 16 Sesarmidae + + + + 17 Ocypodidae + + + + 18 Macrophthalmidae - + + - 19 Gecarcinidae - + + + 20 Diogenidae - + + - 21 Paguridae - + + - (+ present and - absent)

Table 3—Crab species evenness, diversity, richness and index Index Stations 1 2 3 45678910 Pielou’s evenness J 0.9703 0.9775 0.9573 0.9672 0.9626 0.957 0.9726 0.9632 0.9531 0.975 Shannon -Wienner’s 5.6106 5.8875 5.56007 5.8887 5.9008 5.8668 5.8143 5.8013 5.6077 5.5036 diversity(H) Margalef’s(D) Diversity 4.6437 4.9508 4.546 4.9302 5.1218 5.0867 4.8139 4.9283 4.7221 4.412 index Margalef’s(D) Species 11.9421 13.4392 12.3799 14.0946 13.546 13.579 13.434 13.2117 12.339 11.5726 Richness(SR) Simpson’s Index(D) 0.977 0.9816 0.9741 0.9805 0.9809 0.9799 0.9801 0.9793 0.9755 0.9754 682 INDIAN J MAR SCI VOL 43(4), APRIL 2014

a1. C. lophos a2. C. gallus and gastric regions strongly elevated; posterior margin curved laterally; pterygostomial ridge absent; a . M. lunaris a . M. planipes 3 4 ambulatory legs hidden under carapace; the crab has

a5. C. maculatus a6. D. fecchino domed body covers spindly walking legs. This is a . D. quadridens a . A. septemspinosa recorded summer, pre-monsson and monsson and 7 8 absent during post-monsoon seasons. In the present

a9. P. vespertillio a10. S. tranquebarica study it was collected almost all the stations.

a11. S. serrata a12. P. sanguinolentus Box crabs belonging to the family Calappidae

a13. P. pelagicus a14. P. gladiator are morphologically and ecologically diverse group a . P. hastatoides a . P. trituberculatus in shallow water. Colour of C. lophos in dorsal surface 15 16 was uniform tan overall; with rows of widely spaced a . P. vigil a . C. affinis 17 18 spots on posterior surface. Cheliped carpus and palm with purple spots and thick lines on outer surface, a19. C. feriata a20. C. natator clypeiform expansions well-developed; cheliped palm a . C. lucifera a . C. truncata 21 22 with generally smooth outer surface and prominent

a23. C. helleri a24. C. granulata granulate ridge running subparallel to lower margin. This species available almost all the stations of the Plate 1. Crab species recorded during the study in present study. C. gallus chelipeds and carapace different stations mottled yellowish-red and grayish-brown; carapace Discussion convex;clypeiform processes well developed; margins Crabs are one of the fascinating groups in granular with low triangular teeth; cheliped outer Decapoda. They have developed a successful surfaces granulate on lower third and with rounded relationship between the environment and the tubercles on upper two-thirds. Furthermore, the crabs biological mechanisms involved in evolutionary higher on the beach are larger than the crabs found in 21 process15. They are filter feeders, sand cleaners, mud, tidal pools near the low tide mark . Some crabs plant and carrion feeders, predators, commensals and collected in gastropods empty shells, whose shells 22 parasites16. Some are temporary swimmers but most they may then acquire . It is more active at night and of them are walking bottom dwellers. Some even is rarely seen day time by visitors. Since it is usually 23 climbing tress and construct burrows on land17. Out buried in the sediments . This crab was collected not of about 640 species of marine crabs so far recorded only almost all the seasons of a year but also all from Indian waters only 15 species are edible, which stations of the present study. inhabit the coastal waters and adjoining brackish The carapace of spotted moon crab M. lunaris water environments, support commercial with lots of little maroon dots all over the upper part fisheries18,19,20. The marine water ecosystems such as of the body, their paddle-like legs and all legs flattened estuaries, backwaters, saltwater lakes, mangroves etc., are for swimming and digging. Most probably which form the nursery grounds of crabs, are omnivorous, they forage for small fish, worms and increasingly encroached by various purposes. other animals, its inhabitants on sandy to muddy open Crustaceans are well known for their hard, areas, sand flats near mangroves, but often associated calcified exoskeleton, but some regions show with them, sandy silty shores, especially near flexibility, indicating a different structure and seagrasses24. It breeds from September to March with composition. The domed elbow crab C. fornicata a peak in November25 . It is more active at night and collected on a sandy area near seagrasses belonging is rarely seen in daytime, it’s normally burrow just to the family Aethridae. Carapace creamy-beige in below the surface during the day. This species colour; carapace sub-pentagonal; branchial, cardiac collected almost all the stations of the present study. VARADHARAJAN & DARAPANDIAN: CRAB BIODIVERSITY FROM ARUKKATTUTHURAI TO PASIPATTINAM 683

Flower moon crab M. planipes inhabitant’s shallow monsoon and absent in pre-monsoon. This species sandy beach between high and low tide marks to a available almost all the stations except stations 2, 5 depth of 10-15 metres. Carapace rounded with 2 long, & 8 of the present study. well developed lateral spines; anterolateral margins O. reticulates belonging to the family Leucosiidae unevenly serrated. Outer surface of palm with strong was collected in silty, sandy areas near seagrasses. oblique ridge. Carapace with reticulating brown lines They are usually buried under the sand, they feed on forming small rings anteriorly and larger loops small animals in the muds. Its dorsal surface of posteriorly. This crab was not only collected almost carapace with network of granules and depressions, all the seasons of a year but almost all the stations of branchial crests indistinct, median longitudinal ridge the present study. very distinctly separated from rest of carapace by Spotted reef crab C. maculatus is cream to pink fossae on dorsal surface of carapace. This species ground color, with 11 large red spots on dorsal surface available in stations 2, 5, 6 & 8 but absent in other of carapace: 3 on median region, 2 on posterior region, stations. A. septemspinosa carapace is finely granular 2 on anterolateral region and 4 around orbits. It has in irregular patches, front slightly projected, with 2 four blunt spines between the eyes. Maximum was lobes, separated by the median V-shaped notch. collected in pre-monsoon, summer and minimum was Middle of the lateral margin with a slender sharp collected in monsoon. This species available almost spine. Postero-lateral and posterior margins with 5 all the stations of the present study. The leaf porter spines. Chelipeds are symmetrical and slender, carpus crab D. facchino is narrow V-shaped notch is found small, fingers and ambulatory legs slender. Merus between the tips of the frontal teeth; in the young with granules on its dorsal surface, dactylus fringed male the second to the fourth segments of the abdomen with small setae. These two species were observed is each armed with three small tubercles; velvety in maximum in Post-monsoon and minimum in monsoon color. This species available almost all the stations seasons. A. septemspinosa recorded almost all stations of the present study. of the present study. The carapace of E. cristatipes is flat, weakly calcified. Carapace pyriform with The association of the crab D. quadridens with rounded front. The walking legs are flattened. sea anemone is well known. Carapace is sculptured; Dactylus is curved. They do not bear hairs. They were carpus of cheliped with distinct spinules and hairs on collected in estuarine areas. Maximum was in pre- upper surface; palm of chela smooth; flexible hairs. monsoon and minimum in monsoon. This species This species available almost all the stations of the available almost all the stations of the present study. present study. E. indica carapace was longer than broad, its surface with granules, chelipeds unequal, Majidae crabs are commonly known as the spider fingers of large chelae with teeth; second and third crabs. They were collected from the bottom of the pereiopods naked. The crab belonging to dorippidae intertidal area that can be both sand and mud. Crabs family is a scavenger, eating any dead plants or collected in seaweed are covered with long hooked animals that it comes across. Because of the transport hairs, which allow the crab to snip off living pieces behaviour with sea anemones, it is more active at night of algae and attach them to the hairs. A decorated time. At this time, there are few predators above the seaweed crab with algae, sponges and other marine water that can spot them in the dark. So at night, it growths is excellently camouflaged. It only gives itself swims with the leaf under it, to hide from aquatic away when it moves. Young crabs are found in predators below. If it senses danger from above, intertidal areas that have more of seagrass and however, it will quickly flip under the leaf. During seaweeds26,27,28. H. gracilirostris carapace is the day, it often hides under the leaf, half buried in subpyriform, hardly at all setose, with numerous sharp the sand or mud. Maximum was collected in post- tubercles spinules. Especially noticeable are three monsoon, summer and minimum was collected in spinules, longitudinally arranged in the middle line 684 INDIAN J MAR SCI VOL 43(4), APRIL 2014 on the gastric region; carapace, are very slender and frontal teeth prominent, acute, cheliped carpus with have nearly straight fingers. This species available 2 distinct spiniform, spines on outer surface; palm almost all the stations of the present study. Both sexes with 2 distinct distal dorsal spines and spine at carpal of D. gracilipes, was collected at all sampling stations articulation. This species was recorded almost all the of the present study. It lives among rocks encrusted stations of the present study. Carapace of with weeds. Carapace is discoid, second pair of legs S. tranquebarica is usually dark green to black green, three to four times longer than length of carapace; cheliped palm green to purple in life, outer surface single series of tubercles or spines down middle of with reticulate pattern; only males last legs with carapace, the legs covered by fur is dark green; the reticulate pattern present; carapace frontal teeth last two segments of the legs have a reddish tinge. obtuse, usually rounded; cheliped palm with sharp, Carapace of A. lacertosus is smooth, without tubercles but never spiniform, dorsodistal granules; carpus with or spines, regions generally ill defined except 2 distinct spiniform; spines on outer surface. The branchial and cardiac ones, rostrum deeply divided portunid swimming crabs have a broad carapace and by a V-shaped notch, rostral spines very short, flattened hind legs which form swimming paddles and rounded apically. Basal antennal article unarmed and sometimes digging spades. None of the portunids cheliped of adult male long. Maximum was recorded come out onto the shore, but they do enter shallow in post-monsoon and summer and minimum was water to hunt for live food. This species available recorded in monsoon. A. lacertosus was collected almost all the stations of the present study. Colour of almost all the stations of the present study. P. pelagicus males is blue purple dorsally with irregular white lines and spots, especially posteriorly; P. echinatus is a tiny, slow moving crab look like chelipeds and legs especially bright blue with white bits of dirt and junk among seaweeds look very and some ones yellowish reticulations. Females carefully to find them. Elbow crabs are commonly mottled dull green and white. Carapace broad, 2.3 seen in Palk bay shores among seagrasses and times as wide as long; front 4-lobed, medians shorter seaweeds. They are predators of small creatures. In than laterals, cheliped merus with 3 spines on anterior turn, they are eaten by many animals higher up in the border and 1 distal spine on outer border. This species food chain. Maximum was recorded in pre-monsoon available almost all the stations of the present study. and minimum was in monsoon. This species available P. sanguinolentus colour is overall greenish; posterior almost all the stations of the present study. The half of the carapace with three, large, white-bordered common hairy crab P. vespertillio was collected in blood-red spots. Carapace more than twice as broad the plant mudstone area. It is sluggish in its habits. It as long; front 4-lobed; last anterolateral spine is smooth patch can be found near the base of the distinctly larger than preceding spines and directed finger of the large hand, carapace as broad as long, laterally. Cheliped merus outer border unarmed. They convex in the anterior half and depressed in the were collected almost all seasons of a year and also posterior half; surface thickly covered with dark all stations of the present study. brown setae some ones golden-yellow colored setae P. gladiator colour is mottled light and dark (hair) of various lengths, chelipeds asymmetrical, with brown, carapace relatively narrow, about 1.3–1.5 long setae; merus covered with granules and short times wider than long; covered with close-packed pubescence on the outer surface. Maximum was granulated patches with a fine pubescence among the collected in post-monsoon and minimum in summer. granules; cheliped merus with 4 anterior spines and This species recorded only in the stations from 5 to 2 posterior spines. Penultimate segment of male 9. But absent in other stations of the present study. abdomen with straight of faintly convex margins. This Carapace of the mud crab S. serrata is usually species available almost all the stations of the present deep green to olive green; cheliped palm green to study. P. hastatoides overall pale tan, carapace broad, purplish on outer surface, often with reticulate pattern, about twice as broad as long front with 4 lobes; last legs with reticulate pattern in both sexes; carapace cheliped merus robust, with 2 spines on posterior VARADHARAJAN & DARAPANDIAN: CRAB BIODIVERSITY FROM ARUKKATTUTHURAI TO PASIPATTINAM 685 border. P5 merus poster distal margin with 3 or 4 November and another one during May-June,25. This serrations but without spine. Anterolateral angle of species available almost all the stations of the present third maxilliped merus strongly produced. This study. species available only in stations from 3 to 7. But Colour of the ridged swimming crab of C. natator absent in other stations of the present study. The is dorsal pubescence light brown; granules, ridges and carapace colour of P. trituberculatus is olive green margins of carapace maroon. Cheliped mottled with scattered white spots posteriorly, cheliped and maroon and light brown. Carapace surface convex, last leg dark brown-green with white spots. First three uniformly covered with dense short setae; Chelipeds ambulatory legs bluish distally, carapace twice as wide strongly granular, pubescent; P5 propodus posterior as long; front with 3 teeth, median longer than laterals; margin serrated. Large adults, small juvenile last anterolateral spine distinctly larger than preceding swimming crabs are also hidden among the seagrass spines and directed laterally. Cheliped merus with 4 and seaweed and other nooks and crannies. These spines on anterior border and 1 distal spine on outer active crabs come in all kinds of colours, the collected border. This species available almost all the stations species was orangish red overall, with ridges on of the present study. carapace and legs dark and reddish brown. Males Colour of P. vigil is overall greenish brown. outnumbered females in the catch by almost two to Cheliped merus green, remainder dark red-maroon, one, but females were more abundant in catches eyestalks simple, without pterygoid expansions. during June-July, possibly because of increased Carapace about 2.5 times as wide as long, front entire, feeding activity prior to the main spring spawning deflexed. Cheliped palm with spinule on inner distal period. Female had two spawning peaks, a major peak 32 surface. Now it has been under high exploitation, in spring and a secondary peak in autumn . This breeds almost was intense in October and January29, species available almost all the stations of the present absent and poor in summer seasons, peak abundance study. C. truncata is blunt-toothed crab collected in of pre-monsoon season. This species available almost muddy bottoms and seagrass areas, transverse ridges all the stations of the present study. Smooth shelled of carapace faint. A large red impermanent spot on swimming crab C. affinis has a hexagonal, concave either branchial region. Chelipeds not much more carapace with a yellowish-grey colour. It is available than twice the length of the carapace, their upper seasonally, because of peaked in summer and surface more or less granular, their under surface with pre-monsoon seasons30. This species available only smooth-worn squamiform markings. It was intensive in the stations 4 to 8 of the present study. C. feriata breeders and peak season in summer and pre- refers to the red cross on the carapace, colour on the monsoon. This species available almost all the stations carapace brownish with purplish tinge and of the present study. Spiny hands crabs of C. hellerii conspicuous yellow markings, central one resembling was collected in soft bottom, carapace and the a cross; chelipeds purplish brown, spotted with chelipeds dark green and are fully covered with purple yellow, tips light brownish pink. Three spine on on upper. Spine on the posterior margin of the carpus anterior borders of arm, across on the carapace, broad of the fifth leg separates this crab from other species 33 on carapace, slightly convex and smooth, length much of Charybdis and by the presence of the diagnostic 33 less than its width, Fingers as long as the palm, spine on the carpus of the swimming leg . Mostly in chelipeds stout, asymmetrical, denticles on the these crabs can avoid the common types of fishing proximal half. Mostly collected in muddy bottoms, gear. While the considerable crab trapping using throughout the year of collections34,35,36 mangrove marshes and coastal mouths in estuarine . This species available almost all the stations of the present study. environments31. It’s available throughout the year because of continuous breeding activities with two Colour of C. granulata is drab gray-green, mottled peak breeding seasons, one during October– with dull maroon. Cheliped fingers dark maroon, 686 INDIAN J MAR SCI VOL 43(4), APRIL 2014 carapace surface convex, covered unevenly with from sub medians by V-shaped notch, Chelipeds dense short setae, chelipeds strongly granular, finely pubescent. It was collected near seagrass mud pubescent; P5 propodus posterior margin serrated, area, the carapace densely pubescent, granulate in merus posterior margin with sub distal spine. It was postfrontal area, transverse granular lines on collected in the burrows of adult individuals wherever protogastric and mesogastric regions, chelipeds seagrass areas36 , its also intensive breeders and peak covered with large granules and some ones season in summer and pre-monsoon. This species squamiform markings; merus with 3 strong spines and available almost all the stations of the present study. numerous granules on anterior border, posterior Colour of C. rostrata carapace is brownish purple; border granulate. Mostly collected in summer and chelipeds creamy to brownish chocolate colored, premonsoon and the breeding activities are carapace about four-fifth as long as broad, more or seasonally38. This species available almost all the less convex with granular ridges; front prominent and stations of the present study. Thalamita sp preferred cut into six teeth, the middle two teeth remarkably wet water saturated soil beds and mangrove larger and bluntly pointed; Chelipeds nearly smooth, ecosystems39. T. picta could be collected on the shore, less than twice as long as the carapace; hands color on the crabs red and white, carapace closely six-costate and inflated in the male but not so inflated beset with fine hairs only missing at ridges, upper in the female; fingers longer than the palm in the surface of cheliped palm with 2 spines on anterior smaller cheliped and as long as the palm of major and posterior borders, posterior border of propodus cheliped. Sixth segment of male abdomen broader of swimming leg with about 5-7 spines, breeding than long, gently curved and convergent at the sides. activity from summer and pre-monsoon and peaks in There are predominantly found at the lower intertidal the months of February, March and September15. This level and in the adjacent sub tidal, but frequently also species available almost all the stations of the present on rocky sea shore37. This species available all the study. T. chaptali colour is overall dark olive green stations except stations 1, 8 & 9 of the present study. with blackish mottling, carapace surface sparsely Colour of C. japonica is overall drab green dorsally. pilose; cheliped palm smooth, with 5 dorsal spines; Cheliped fingers maroon and blue. Ambulatory legs outer surface with costa on lower half extending onto green with purplish tinge, carapace pilose; with pollex; fingers with simple tips. Basal antennal 6 triangular frontal teeth, medians inclined slightly segment smooth, without spines or tubercles and this laterad; with finely granular protogastric ridges, is found to be seasonal being available only during mesogastric, metagastric and epibranchial ridges. summer and pre-monsoon season, it was intensive Cheliped merus with 3 spines on inner border; breeds almost throughout the year, except in summer propodus with 5 dorsal spines. This species absent in in the month of March, April and pre-monsoon in the stations 8 to 10. But present in other stations of the month of September. This study is in agreement with present study. The colour of C. miles carapace and the earlier study of 40 in Portonovo coast. This species ambulatory legs are pale orange-pink. Chelipeds recorded only the stations from 2 to 7. The colour of mottled orange and white, carapace surface convex, T. crenata is overall dark brownish green; cheliped with dense short setae; with 6 sharp frontal teeth; inner fingers maroon, carapace surface smooth, sparsely oribital lobe sharp; surface with protogastric ridges, pilose; all anterior carapace ridges present, Basal mesogastric, epibranchial and metagastric ridges and antennal segment granulate. Cheliped palm upper chelipeds elongate. This species available almost all surface bearing 5 spines, outer surface smooth with the stations of the present study. single ridge running to pollex, inner surface smooth. The colour of C. variegata is overall light sand This species available almost all the stations of the with light brown mottling, carapace surface pilose; present study. T. sima carapace is covered densely with 6 frontal teeth, medians triangular, projecting with short hairs, 3 pairs of gastric ridges, basal anteriorly beyond sub medians, laterals separated antennal joint with a smooth, short and curved crest. VARADHARAJAN & DARAPANDIAN: CRAB BIODIVERSITY FROM ARUKKATTUTHURAI TO PASIPATTINAM 687

Upper surface of cheliped palm with 1 spine on straight. Thoracic sternites 2 and 3 separated by anterior and 2 on posterior borders, posterior border conspicuous suture. Cheliped propodus with of propodus without spines, hand of cheliped with conspicuous tomentum, dorsal margin keel-like and squamiform markings (except in juveniles), male first are adapted to a specific existence with seagrass, pleopod with flared tip. Swimming crabs were where they find protection among branches of commonly seen in all seashores. They are particularly seagrass. The extensive ecological distribution of active at night, but are often also out and about during these crabs parallels the dispersal of the corals with the day. Besides the large adults, small juvenile which they are habitually associated. The crab feeds swimming crabs are also hidden among the seagrass on the mucus produced by the coral, gathering these and seaweed. They eat fish, worms, other crustaceans, with the minute comb-like structures at the tips of snails and clams. They may also nibble on seaweed. their feet. Maximum was recorded in summer and It is breeds almost throughout the year41, peaks in minimum was recorded in monsoon. This species summer in the months of January, March and pre- recorded in the stations of 2 to 7 and absent in other monsoon in the months of August and September, stations. absent in April and July42. This species available The crabs belonging to the family Xanthidae are almost all the stations of the present study. essentially herbivorus, normally grazing on plant The crabs belonging to family Potamidae were origin and coral growing near their place and on found collected near inshore of coastal areas. The carapace which drifted into their hiding place. Several seem to of S. spinigera is physiognomy and the diagnostic be widely dispersed without reference to any spine on the dorsal sub distal part of the cheliped particular environment within a given area, wandering merus. This species recorded all stations except 1, 3 at random and seeking concealment under seagrass, & 10. S. hydrodroma carapace is strongly convex, stones or in crevices of dead. Convinced species of cervical groove distinct but appears superficial; it Paractaea, Leptodius, Zozymodes and Demania are disappears behind the post-orbital tresis and orbit typical of the shoreline, often concealing themselves horned. The notch-lateral borders of carapace strongly under stones in the intertidal zone. These forms, which convex, cristiform and smooth, postero-lateral borders live in moist environments but out of water for ill defined. Three terminal segments of the male considerable periods of time, are highly tolerant of abdomen are slightly narrower in comparison to the fresh water, surviving heavy downpours of rain basal segment. This species available almost all the without apparent ill effects. stations of the present study. The shape of P. fluviatile The carapace of P. neospeciosa is broadly oval is roughly square, with the reduced abdomen tucked in shape. The entire carapace is divided very cleanly beneath the thorax. The thorax bears five pairs of legs, into regional and subregional convex lobules. In the first of which is armed with large claws, the males female chelipeds are equal, stout, the lobules on outer being normally larger than females. The crabs were surfaces of wrists and on upper edge of hands are available maximum in pre-monsoon and monsoon and distinctly outlined and one granular longitudinal line minimum in post-monsoon and summer seasons. The present on the middle of outer surface of palms. Lower crab P. fluviatile was available almost all the stations half of palms are granular; base of dactylus is also of the present study. granular. Tips of the fingers are pointed. This species The common name of T. cymodoce is red coral absent in station 1 but recorded all other stations of crab or orange coral crab. The colour of carapace is the present study. The colour of L. exaratus is overall purplish to brownish blue, with transverse row of pale dirty brown, carapace regions projecting, rugose orange-red spots. Cheliped dactylus black on distal and separated by deep grooves; with 4 anterolateral two-thirds. Carapace dorsal surface with transverse teeth behind outer orbital angle. This crab was row of orange-red spots; anterolateral margins nearly available almost all the stations of the present study. 688 INDIAN J MAR SCI VOL 43(4), APRIL 2014

Z. cavipes has carapace surface with irregular scramble quickly among slippery rocks. Colours seen rugosities composed of granules often arranged in range from reddish to bluish and greenish. It is a short transverse groups or striae; anterolateral margins scavenger and also eats seaweeds. It is more active at with 4 short, narrow teeth each intervened by smaller night and seldom seen during daylight. This species tooth. Cheliped carpus and propodus deeply pitted available almost all the stations of the present study. and eroded. This species represented only in stations The colour of G. strigosus is dark reddish brown and 2, 5, 7 & 9. white, carapace depressed, naked, smooth between D. buccalipes carapace and chelipeds covered the ridges, branchio-cardiac groove indistinct, with large depressed tubercles; carapace about external surface of cheliped palm smooth, bearing two seven-ninth as long as broad. The characteristic indistinct ridges, finger tips coloured dark tan or tubercles have everywhere a worn appearance, brown. Inferior distal extremity of last pair of especially in the middle of the carapace and on the ambulatory legs serrate. Male abdomen with sixth chelipeds and the ischium of the external maxillipeds. segment equal to or shorter than fifth. Male first Dorsal crest of the arm and of the meropodites of the pleopod straight and very stout. This species absent legs have each become a row of berry like teeth and only in station 10 and present all other stations of the the serrated crest and granular ridges of the present study. The carapace of M. messor legs are carpopodites and propodites of the legs have become brownish green and irregularly mottled. Claws merely low rough elevations. Bright and distinctive brownish red with clearer tips. Male abdomen with color pattern of this species is characteristic of many sixth somite shorter than fifth somite. This mangrove known poisonous species and is an indirect crab can be found in belt mangroves43 and on rocky confirmation of their toxicity. These crabs are shores44. This species absent in stations 1 & 9 and available all seasons except post-monsoon. This present all other stations of the present study. species available only in stations 2, 5, 6 & 8 of the M. maculates morphological colour of dark bottle- present study. green, the claws in some adult males are a brilliant violet, in others bright orange, dull in the female; the Oziidae crab O. rugulosus was collected near the legs are striped with alternate light and dark bands, seagrass mud area and identified by its carapace carapace being seven-eighths as long as broad, with thickly covered with fine granules and pits, but the markedly convergent sides and the absence of posterior half of the dorsal surface is almost smooth transverse markings on the post-frontal region. The to the unaided eye, antero lateral border rather faintly fingers of the chelipeds are much longer than the divided into 5 lobes, of which the first two are broad and rounded and the last three are bluntly acuminate. upper border of the palm. Except in the last pair of Legs stout, the last three joints. It is more active at legs, the greatest breadth of the meropodites is night, but even so, very quick to scuttle back into decidedly less than half their length. The terminal hiding when disturbed. Maximum was recorded in male abdominal segment has a three-lobed post-monsoon and minimum was recorded in appearance. This species only absent in 3 & 10 and monsoon. This species obtained only in stations 2, 5 recorded all other stations of the present study. Pebble & 6 of the present study. crab L. pubescens is a rounded and colour is shiny olive green, chelipeds and legs with brownish bands. Grapsidae crab, G. albolineatus is circular shape It is distinguished by the sharply hexagonal carapace. in dark with a pattern of light spots in bands at the Long legs; Pterygostomian convex. The male lower portion of the body. Short small flattened abdomen consists of three segments. Maximum was pincers. Very long walking legs tipped with pointy recorded in summer and minimum was recorded in claws. With these legs, the crab clings tightly so it post-monsoon. This crab absent only in the station 3 doesn’t get washed away in the waves and can and recorded all other stations of the present study. P. VARADHARAJAN & DARAPANDIAN: CRAB BIODIVERSITY FROM ARUKKATTUTHURAI TO PASIPATTINAM 689 globosa is smoky bluish brown above, the blue post-monsoon and monsoon seasons may be attributed deepest on the carapace. Carapace smooth, its regions for greater abundance in seasons and categorized them hardly defined. Epistome projects beyond the front, as permanent inhabitant seasonal immigrant and which hardly pubscent. Sixth abdominal tergum casual visitors45. They were recorded in intertidal smooth. Maximum was recorded in monsoon and areas and feeding strategies of scavengers and will minimum in post-monsoon. This species present in eat almost anything, plant origin, such as seagrass stations 1 to 6 and absent in all other stations of the and seaweed46. This species available almost all the present study. stations of the present study. Large crab or sponge crab D. dormia has brown S.brockii is a tree climbing species from coastal colour, white or pink claws tip. Dome shaped carapace mangroves. It is commonly found underneath the bark much wider than long, strongly convex, antero-lateral of dead trunks or inside hollow trees in mangroves. borders armed with four teeth, covered with thick and Carapace quadrate to longitudinally rectangular, rough hair; Short conical lateral spines, chelipeds lateral margins parallel to subparallel or gently massive, outer face of palm inflated, inner superior divergent posteriorly. Cheliped merus with expanded margin with four tubercles. This species available foliaceous distal margin, lined with prominent sharp almost all the stations of the present study. Tidal spray spines and teeth. Chelae with stridulating structure; crab P. depressa tuberculata colour is reddish brown male telson slightly longer than wide; all somites free. or light reddish, dotted with blood red, tubercles Maximum was recorded in post-monsoon and bordered with blackish haris having gray extremities; monsoon and minimum was recorded in pre-monsoon. blood-red spots on legs; underside of body yellowish, It was recorded throughout the year including low chelipeds with purplish spots and stripes, this crab is saline of monsoon47. This species available almost distinguished by the absence of a true front, so that all the stations of the present study. the antennular fossae are visible in a dorsal view as Colour of S. bidens is flattened deep red deep clefts in the anterior border of the carapace. The and brown shell with protruding eye stalks and regions of the carapace are distinct, and covered with 2 equal-sized orange to bright red claws. Carapace flat pearly or squamiform tubercles. The antero-lateral subquadrate, surface almost flat, covered with fine borders are cut into four teeth. The chelipeds are piles and the ridges of the postero-lateral surface also massive and have tubercles on the upper surface of furnished with piles. Merus of the chelipeds short, the palm and finger arranged in longitudinal rows. prismatic, with a strong subdistal spine on its inner They live in sandy, muddy and sea grass areas and border. Carpus convex, rugose, the inner- distal angle are often found buried in the soft bottom during day. bluntly rounded. First pleopod of the male straight, Maximum was recorded in summer and monsoon and the distal chitinous process bent ventrally outwards. minimum was recorded in post-monsoon. This species Abdomen triangular; telson semicircular distally. available almost all the stations of the present study. Males are more brightly coloured than females. The Grapsidae crabs mostly collected in large Females also have a different shaped abdomen, only number in seashores. They may be distinguished by visible on the underside. Maximum was recorded in their broad fronts, short eyes and almost square shaped monsoon and minimum was recorded in pre-monsoon. carapace. Mostly grapsids have equal sized chelae This species available almost all the stations of the (claws), unless one has been broken off and is present study. regrowing. The male grapsids usually have much Carapace of S. plicatum is broader than long, the larger chelae than females of the same species. The dorsal surface moderately convex and uneven but factors such as low salinity and temperature possible generally naked and glabrous. Eyestalk relatively physical changes in the substrate composition and short. Chelipeds of female smaller than those of males, availability of maximum organic materials during granulate than that of males, without pectinated crests; 690 INDIAN J MAR SCI VOL 43(4), APRIL 2014 tubercles on upper surface of movable finger not The carapace of U. lactea is white or gray black. prominent. Walking legs medium sized, flattened Major cheliped white. Carapace front broad; merus relatively wide that of second walking leg. anterolateral margin almost straight, major cheliped Merus of ambulatory legs is almost twice as long as of male without longitudinal groove on outer surface broad. This species available almost all the stations of pollex and dactylus. This species available almost of the present study. S. tetragonum is a square shaped all the stations of the present study. Immobile lower parallel lateral side with one acute tooth behind outer finger U. vocans is orange or yellow and has a long orbital spine. All the regions especially the gastric groove on the outside. Body colours and patterns vary, well defined, whole dorsal surface covered with tufts some greenish, others greyish. Male fiddler crab’s of hairs, longer and thicker anteriorly. In male, enlarged pincer has a bumpy outer face. Tips of the chelipeds stouter and more sharply rugose on outer pincers are flattened and sabre-like. O. ceratophthalmus surface than in females. Maximum was recorded in can be distinguished from other related crabs by the pre-monsoon and summer and minimum was recorded eyestalks extending beyond the eyes into long points, in post-monsoon. This species available almost all which are longer in males and shorter in females and the stations of the present study. S. batavicum has its juveniles. Crabs have a box-shaped body, across the carapace, square, deep, broader than long; lateral carapace, with darker markings towards the rear in sides slightly convergent posteriorly and without teeth the shape. They were collected in sandy beaches and behind the outer orbital angle. Small transverse rows sand flats in front of mangroves. This species present of setae present on carapace. Chelipeds in male equal, in stations 2, 4, 5, 6 & 8 and absent in all other stations outer sides of arm and wrist rugose. Patch of long of the present study. Carapace of O. macrocera has a thick hairs present at the finger cleft in all males. In carapace faint reddish-chestnut color. Chelipeds are females no dent on dactylus present and few long hairs red at the base with red spine and the outer surface of on finger cleft. Anterior edge of carpus and propodus densely setose. Moveable finger of male chelae the large claw is bright orange. The walking legs are differentiate the species. This crabs collected in frenching grey in color. carapace square, deep, mangrove, intertidal and muddy substratum. strongly convex from before backwards and Maximum was recorded in monsoon and minimum moderately so from side to side; surface covered was recorded in pre-monsoon. This species available uniformly with bubble like small granules; cheliped almost all the stations of the present study. not pointed but expanded and blunt, length of stridulating ridge on inner side of palm, more than The crabs belonging to family Grapsidae and half of the breadth of larger palm, this ridge consists Ocypodidae were the principal forms, which of striae only, hairs scanty. This species available participate a very important role in recycling the almost all the stations of the present study. D. nutrients enhancing the role of decayed plant materials myctiroides across the carapace, and they are and litter processing48. Colour of U. annulipes in characterised by the presence of “gas windows” on enlarged pincer is usually pink, sometimes nearly the merus of the legs; in Dotilla, these windows are white. The body is often black with blue or white also present on the thoracic sternites. Sand bubbler stripes; the male fiddler crab’s enlarged pincer has a crabs live in burrows in the sand, where they remain ridge of bumps on inside or the ‘palm’ of the pincer. Outer side is smooth and does not have a triangular during high tide. When the tide is out, they emerge depression. Movable upper finger extends past the on to the surface of the sand and scour the sand for immobile lower finger. This small crab with an food, forming it into inflated pellets, which cover the enlarged pincer that is smooth is sometimes seen on sand. However in moist, semi-fluid and unstable some of the Indian shores. Sandy, silty shores near substrate, it rotates in the sand creating pellets and the low water mark, often near mangroves. This uses it to seal the opening roof. It was collected in all species available almost all the stations of the present stations and maximum was recorded in pre-monsoon study. and minimum in post-monsoon and totally absent in VARADHARAJAN & DARAPANDIAN: CRAB BIODIVERSITY FROM ARUKKATTUTHURAI TO PASIPATTINAM 691 monsoon season. This species available almost all the plainly visible to the naked eye, its length in the male stations of the present study. about two-thirds of its breadth; eyestalks slender, hardly curved, the eyes reach almost to the end of the The other groups of shore crabs are belonging to orbital trenches; the chelipeds and legs are unarmed the family Ocypodidae. They are mostly in tall eyed, except for a small sub-terminal denticle on the anterior with the bases of their eyes close together at the front border of the meropodites of the first three pair of of the carapace. Ocypodid crabs were collected live legs. Maximum was recorded in summer and on sandy beaches, mudflats and in mangrove swamps. minimum was recorded in pre-monsoon. They were They are active burrowers and many live in collected in sediment of the undisturbed and the 49,23 colonies . Density of these crab are high compared logging areas both silty clay in the mangrove and 50,51 to other brachyurans . Diet includes algae, tiny crab shore sediment. This species absent in stations 1, 3, pellets and freeze dried plankton and shrimp. It is 7, 9 & 10 and present all other stations of the present consists as a main food items for a large number of study. fauna, being responsible for an important part of the macrobenthic production in the intertidal zone. Male C. carnifex is found in coastal regions of Palk 57,58 ghost crabs and especially the fiddler crabs have Strait . Species is large dull, dark reddish brown unequal sized chelae52. Uca sp mostly collected with a deep transversely oval carapace with rounded intertidal mud flat area 53. Population of U. annulipes, sides to allow for the expanded gill chambers. Both U. lactea and U. vocans inhabitant area between high sexes were collected however larger males the water neap and low water neap before the onset of chelipeds are conspiculously unequal and large females have rather unequal chelipeds. The crabs monsoon seasons. Migration Uca sp during monsoon collected in near mangroves and its burrows under season to distance of twenty five meter away from coconut trees and dried mud59,60. They are the pre-monsoon habitat54. It is also suggests that occasionally seen above ground during the daytime33. reproduction is continuous, a very common pattern Maximum was recorded in summer and pre-monsoon in tropical brachyurans. Major peaks of spawning and minimum was recorded in monsoon. This species occur during the summer and subsequently decline available almost all the stations of the present study. in winter55,56. The hermit crabs belonging to family Diogenidae Macropthalmus sp were collected mostly in low and Paguridae were recorded in varies places in wood, tides, normally the population density of this species shells61,62 and seagrass meadows. In Diogenidae, the was not much as found in their family Calappidae. left chela that is enlarged instead of the right, because Colour of the M. convexus carapace is slate purple in contrast to most other hermit crabs. The presence with maroon spots. Ambulatory legs gray-lilac; dactyli of crabs in gastropod shells, the crabs to occupy dark pink, carapace broadest anteriorly, surface finely virtually all suitable shells. The cephalothorax colour granulate except frontal, protogastric and mesogastric of C. longitarsus is green-brown with darker brown regions; eyestalks not extending beyond apices of mottling and patches with dark sub medial lines outer orbital angle. Cheliped palm about 2.5 times as posteriorly. Ocular peduncles dorsally olive green, long as high, merus of first three ambulatory legs ventrally very pale green or cream. Shield longer than dorsally setose. Maximum was recorded in summer broad. Chelipeds sub equal, right slightly longer and and minimum was recorded in pre-monsoon. This more robust, similar in armature; dorsomesial margin species available almost all the stations of the present of palms each with row of 4 spines, dorsal surfaces study. Sediment may play a role as an appropriate with 1 or 2 irregular rows. This species available habitat for the dominant species M.-depressus, the almost all the stations of the present study. The colour of the crab is greyish carapace broader than carapace colour of C. arethusa is white or light grey; long, tooth at anterolateral angle of carapace truncate eyestalks, antennules, antennae, chelipeds and legs and square cut; surface of palm of male smooth; deep orange red with black tipped fingers of chelipeds carapace studded with minute granules not always and dactyli, eyestalks shorter than antennular 692 INDIAN J MAR SCI VOL 43(4), APRIL 2014 peduncles; ophthalmic scale narrow, pointed at tip the forest edge near the high tide mark and the other and close together; numerous tufts of setae on gastric approximately 10 m from the tree line near the low region and behind cervical groove; antennal acicle tide mark, with few crabs in between 63. Accordingly reaching about one-third last antennal segment; a few different habitats such as seagrass, seaweed and conical spinules with blunt tips on hand and virist; mangroves compared hermit crabs mostly collected dactylus of third pair of legs of same length as and abundance in gastropod shells64, as well as the propodus; propodite with flattened outer surface; but gastropod shells can be limiting resources to hermit devoid of superior external carina. This species crab populations65. So many studies previously represented only in stations 5, 6, 8, & 10 of the present discussed shell occupation by hermit crabs65,66. The study. The colour of C. olivaceus carapace and legs hermit crabs abundance can be influenced by are green in color, 3 red lines, 1 on the dorsal side physico-chemical conditions, for instance selecting and 2 on the lateral sides are present on eyestalks. On heavier shells in areas of high water turbulence and the merus and carpus of walking legs brownish dark wave action65. Maximum was recorded in summer spots are seen. Formalin preserved specimens are and minimum was in pre-monsoon and absent in yellowish with the chelipeds and other legs red in post-monsoon and monsoon. This crab was recorded color, eyestalks as long as the antennular peduncles almost all stations except station 10 of the present as but distinctly longer than the anterior border of study. the carapace. Chelipeds sub-equal and similar. This Fiddler crabs approximately 100 species of semi crab absent only in station 1 and present all other terrestrial marine crabs which make up the genus Uca. stations of the present study. Hermit crabs 1100 species are decapod crustaceans The carapace colour of D. megistos is bright of the super family Paguroidea. The infraorder red-orange with numerous white spots ringed with Brachyura contains 6,793 species in 93 families, as black. Ocular peduncles bright red-orange with few many as the remainder of the Decapoda. Freshwater tiny darker red spots. Antennular and antennal crabs more than 1,280 species that comprises the 67,68 peduncles red-orange. Chelipeds and ambulatory legs largest group within the Brachyura reported 254 bright red-orange with numerous white spots ringed species of crabs belonging to 120 genera which with black. Setae generally dark red, ocular peduncles represented 24 families. A total number of 990 species moderately long and slender; corneas only very of marine brachyuran crabs belonging to 281 genera and 36 families are found in Indian waters14. In the slightly dilated, setose and weakly spinose. Chelipeds present study totally 21 families represented by 79 and ambulatory legs, especially three distal segments crab species were recorded. The species contributions each thickly covered with tufts of long bristles and of different families were in the following order; corneous-tipped spines. Chelipeds grossly unequal Aethridae 1, Calappidae 4, Carpillidae 1, Dorippidae and left larger. These crabs are available all seasons 3, Leucosiidae 2, Hymenosomatidae 1, Majidae 3, except post-monsoon and monsoon. This crab Parthenopidae 2, Pilumnidae 1, Portunidae 24, represented only in stations 5 to 9 of the present study. Potamidae 3, Trapeziidae 1, Xanthidae 4, Oziidae 1, S. spirifer is overall brownish-orange, shield Grapsidae 9, Sesarmidae 5, Ocypodidae 6, broader than long; rostrum broadly subtriangular. Macrophthalmidae 2, Gecarcinidae 1, Diogenidae 4 Chelipeds slender, similar, of equal length or right and Paguridae1. This study agreement with earlier slightly larger; chela with marginal fringe of long studies along Indian coast by69 recorded 27 species setae; Dactyls of ambulatory legs each with row of of crabs belonging to the three families Portunidae, long setae on dorsal margins; male left sexual tube Ocypodidae, and Grapsidae Alcock8,70 in his stout, long, coiled and lateral margins each with few ‘Materials for a Carcinological Fauna of India’ prominent spines. Paguridae crabs found two described 35 species of portunids, 13 species of aggregations on the beach at low tide, one close to ocypodids and 24 species of grapsoids from the VARADHARAJAN & DARAPANDIAN: CRAB BIODIVERSITY FROM ARUKKATTUTHURAI TO PASIPATTINAM 693

Andaman and Nicobar Islands. Brachyuran fauna of in Gulf of Mannar.89 Among 57 species of crabs the Maldive and Laccadive Archipelagos were belonging to 37 genera and 11 families were recorded initiated by8,70 who recorded 43 species of crabs from three lakes, such as Chilka, Pulicat and belonging to 9 families. Subsequently,71,72,73,74,75 Vembanad Lake. List of species following families reported 191 species of crabs including 27 already in Calappidae (3), Leucosiidae (3), Hymenosomatidae described by76 which brought up the total record from (3), Majidae (1) Portunidae (10), Pilumnidae (2), this region to 207 species.65 were reported crabs Gecarcinidae (1), Grapsidae (15), Pinnotheridae (1), belonging to Portunidae, Ocypodidae, Grapsidae and Ocypodidae (16), Gecarcinidae (2). Similarly 36 Mictyridae and described 29 species besides few new species of crabs were recorded in Pichavaram records from Andaman and Nicobar islands18. mangrove environment by90. Recently91 were reported reported 68 species coming under 14 families of crabs in Cuddalore coast. Totally 13 families were brachyuran crabs along Parangipettai coast. The crabs recorded coming under 31 genera which represented along Pitchavaram mangrove represented by Calappidae (6), Carpillidae (2), Corytidae (1), Calappidae 3, Dromidae 2, Dorippidae 1, Dromidae (2), Dorippidae (2), Grapsidae (2), Geocarcinidae1, Goneplacidae 2, Grapsidae 11, Goneplacidae (1), Leucosiidae (6), Majidae (6), Leucosiidae 7, Majidae 1, Ocypodidae 9, Ocypodidae (2), Portunidae (23) and Xanthidae (8). Parthenopidae 4, Pinnotheridae 2, Portunidae 30 and In the present study maximum crabs were 46,77 Xanthidae 4 was recorded by reported 29 species collected during summer and monsoon than of crabs from Pulicate Lake. Totally 105 species pre-monsoon and post-monsoon. The crabs belonging belonging to 16 families coming under 56 genera to families viz., Calappidae, Portunidae, Potamidae, which includes, Calappidae 5, Dromidae 2, Grapsidae, Sesarmidae and Ocypodidae were Dorippidae 2, Goneplacidae 1, Grapsidae 2, obtained almost all seasons. Some scientist already Leucosiidae 11, Majidae 13, Ocypodidae 2, reported that the crabs abundant maximum in Parthenopidae 4, Portunidae 23, Xanthidae 8, monsoon92,85 post-monsoon, summer and minimum Carpillidae 3, Menippidae 1, Zosiminae 7, ETisinae1, in monsoon and pre-monsoon35,93. Chlorodinae 6, Cymoinae 2, Actaeinae 2, Pilumnidae 3, Trapeziidae 4, Aethrinae 1 and Plaguiidae 2 Each and every substrate is preferred by a specific reported by78 from Gulf of Mannar.79 reported 18 community of animals that are often limited to that species of crabs in Sundarbans,80 recorded 18 species habitat, a behavioral response such as modified in Pazhaiyar and Parangipettai coast.81 reported 16 feeding habits94. Burrowing activity of crabs in species of crabs in Cuddalore coast.82 reported 34 mangroves, seagrass and salt marshes may strongly species of crabs in Mudasalodai and 32 species in affect the substratum landscape95. Loss of habitat is Nagapattinam coats.83 obtained 12 species in Kerala the primary cause of species loss96. Among the, most coast and84 recorded 38 species in Pichavaran productive plant communities, providing habitat and mangroves.85 recorded 43 species of crabs belonging food for a variety of crustaceans97,98. Seagrass beds to family Dromidae (1), Dorippidae (1), Leucosidae have a very high productivity rate and contribute (9), Calappidae (5), Matutidae (2), Majidae (2), significantly to the total primary production of inshore Parthenopidae (2), Portunidae (16), Xanthidae (3), waters. Its serve as a number of important functions Graspidae (1) and Corystidae (1) was reported in trawl in inshore areas. They are significant source of food by catch in Kerala coast. Forty six species of crabs for many organisms both by direct grazing and detritus belonging to the family Portunidae, Podaphthalmidae, feeding and have usually been considered the Ocypodidae, Sesarmidae, Dromidae and Dorippidae principal and optimal nursery grounds for many were reported in five different stations of Pichavaram decapod species 99,100,101. On the seashore a very large mangrove by86,87 recorded 9 species of crabs in number of different species of crabs (Ocypodiae, Pondicherry coast and88 recorded 67 species of crabs Sesarmidae, Portunidae) are found, but most of them 694 INDIAN J MAR SCI VOL 43(4), APRIL 2014 are smaller in size and therefore rarely for human understanding of the structure and functioning of the consumption. 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