Introduction
The northeast coast of India lies between latitude 16°N to 21°N and longitude 81°E to 89° E off the Bay of Bengal (Figure 1). It exhibits a diverse range of coastal morphologies and is rich in biodiversity. The coastal morphology is influenced by the prevailing oceanographic condition of the Bay of Bengal. In addition, it is home to the deltaic region of major rivers, such as Brahmaputra, Ganges, Meghna, and Godavari. These deltas have extensive mangroves, estuaries, and shell beds providing critical habitats for various species of fishes, shrimps, birds, and other wildlife. Some parts of the northeast coast have rocky shores and reef patches (Silambarasan et al., Reference Silambarasan, Kar, Prasad, Pattnayak and Ramalingam2022). These areas provide habitat for intertidal and subtidal marine life, including various species of crabs, molluscs, and algae (NCSCM, 2010).
Figure 1. Sampling locations during cruises of MFV Matsya Shikari and MFV Matsya Darshini stations with the presence of brachyuran crabs.
Exploratory bottom trawling operations are conducted since 1960s by the Fishery Survey of India (FSI) with intensive coverage along the northeast coast of India, off Andhra Pradesh, Odisha, and West Bengal between latitudes 16°N to 21°N and longitudes 81°E to 89°E (Naumov, Reference Naumov1961; Borisov, Reference Borisov1962). The surveys conducted by the Royal Indian Marine Survey Ship ‘Investigator’ provide scientific research on the existence of many species of brachyuran crabs in India (Wood-Mason and Alcock, Reference Wood-Mason and Alcock1891; Alcock and Anderson, Reference Alcock and Anderson1894a, Reference Alcock and Anderson1899; Kemp, Reference Kemp1923). The first comprehensive study of brachyuran fauna on the Andhra Pradesh coast was carried out by Wood-Mason and Alcock (Reference Wood-Mason and Alcock1891). Subsequently, in a series of publications, Alcock (Reference Alcock1894–1901) documented brachyuran fauna in India. Lalitha Devi (Reference Lalitha Devi1981, Reference Lalitha Devi1986) later recorded three species of pinnotherid crab from Kakinada. Devi et al. (Reference Devi, Shyamasundari and Rao1988); Devi and Shyamsundari (Reference Devi and Shyamsundari1989); and Devi (Reference Devi1991, Reference Devi1993) compiled brachyuran crab diversity on the Visakhapatnam coast and listed 24 species of portunid crabs. Dev Roy and Bhadra (Reference Dev Roy and Bhadra2001) recorded 14 species from the Godavari estuary. However, Dev Roy and Bhadra (Reference Dev Roy and Bhadra2005) examined 21 species of brachyuran crabs from marine, estuarine, and mangrove habitats along the Andhra Pradesh coast. Other smaller collections of brachyuran crabs from the northeast coast of India are made by Deb (Reference Deb1987); Dev Roy and Nandi (Reference Dev Roy and Nandi2008); Mitra et al. (Reference Mitra, Misra and Pattanayak2010); Dev Roy (Reference Dev Roy2017); and Srivastava (Reference Srivastava2017). Trivedi et al. (Reference Trivedi, Trivedi, Vachhrajani and Ng2018) compiled a checklist of the brachyuran crabs of India, listing 910 species. Recently, Silambarasan et al. (Reference Silambarasan, Kar, Prasad, Pattnayak, Das, Bhami Reddy and Ramalingam2023) recorded some commensal anomuran and brachyuran crabs in the northwestern Bay of Bengal.
The present study deals with incidental records of the brachyuran crab fauna of the northeast coast of India based on the material collected during extensive exploratory fishery survey cruises carried out by the FSI Research vessels MFV Matsya Shikari and MFV Masya Darshini, which include 81 species from 46 genera and 19 families. Out of 81 species, 21 are new records from the northeast coast and 1 new record on the mainland coast of India.
Materials and methods
The samples were collected during nine survey cruises of MFV Matsya Shikari and MFV Matsya Darshini attached to the Visakhapatnam Base of the FSI, under the Government of India, Ministry of Fisheries, Animal Husbandry & Dairying, Department of Fisheries over a period of 2 years from 2018 to 2020 (Figure 1). Specimens were collected in trawl by-catches in the demersal fishery resources survey, assessment, and monitoring programme from depth ranges of 30 to 200 m. Each haul lasted for a duration of 90 min, with a towing speed of 2.5 km h−1. Samples were sorted and identified onboard up to the species level. For each species all the specimens were counted, weighed, and photographed. The identification process utilized various tools, including microscopes for detailed morphological examination and a Nikkon Z50 mirrorless camera for capturing high-resolution photographs. A representative collection of each station and of each species was preserved in 10% formalin and stored for further studies in a laboratory. All the specimens were examined and deposited in the Referral centre of the Fishery Survey of India Museum, Visakhapatnam, Government of India, Ministry of Fisheries, Animal Husbandry & Dairying, Department of Fisheries (FSI/VIZAG/CRUST).
Measurements provided are of the maximum carapace length and width respectively. The classification of terminology was followed Ng et al. (Reference Ng, Guinot and Davie2008) and Davie et al. (Reference Davie, Guinot, Ng, Castro, Davie, Guinot, Schram and von Vaupel Klein2015).
Out of 81 species collected, 21 are new from the northeast coast of India, though they are recorded from other parts of Indian coast. A brief systematic account for each 21 new recorded are dealt with here. A complete list of 81 species is given in Table 1.
Table 1. List of brachyuran crabs collected from the northeast coast of India
Species names in bold (with asterisk, *) are new records.
Results
Systematics
Section PODOTREMATA Guinot, 1977
Subsection: HETEROTREMATA Guinot, 1977
Superfamily DORIPPOIDEA MacLeay, 1838
Family DORIPPIDAE MacLeay, 1838
Dorippe frascone (Herbst, Reference Herbst1785)
(Figure 2A)
Material examined
1 male (32.1 × 33.0 mm2), 19°48.9′N/83°33.4′E, 41–42 m, coll. K. Silambarasan, 24 December 2019.
Figure 2. Overall dorsal habitus: (A) Dorippe frascone (Herbst, Reference Herbst1785) male (21.2 × 19.3 mm2), (B) Calappa capellonis (Laurie, Reference Laurie and Herdman1906) 1 male (40.0 × 35.2 mm2), (C) Calappa gallus (Herbst, Reference Herbst1803) 1 male (20.2 × 14.0 mm2), (D) Calappa exanthematosa (Alcock & Anderson, 1894) 1 male (63.0 × 86.0 mm2), (E) Calappa clypeata (Borradaile, Reference Borradaile and Gardiner1903) 1 male (20.7 × 32.0 mm2), and (F) Leucosia anatum (Herbst, 1783) female (18.6 × 21.1 mm2).
Restricted synonymy
Cancer frascone Herbst, Reference Herbst1785, p. 192; Dorippe (Dorippe) frascone Krishnamoorthy, Reference Krishnamoorthy2007, p. 90; Dorippe frascone Ng et al., Reference Ng, Guinot and Davie2008, p. 59; Dorippe frascone Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018, p. 33.
Distribution
India
Tamil Nadu (Krishnamoorthy, Reference Krishnamoorthy2007; Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018), now from as northeast coast as the new record.
World distribution
The Philippines and Indonesia (Holthuis and Manning, Reference Holthuis and Manning1990); Taiwan (Chou et al., Reference Chou, Lai and Fang1999).
Remarks
This species is always associated with sea urchins and sea anemones (Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018; Silambarasan et al., Reference Silambarasan, Kar, Prasad, Pattnayak, Das, Bhami Reddy and Ramalingam2023). According to Krishnamoorthy (Reference Krishnamoorthy2007), the species occurred throughout the year along Chennai coast and found carrying a bivalve over its carapace, with the help of hooked third and fourth legs.
Superfamily CALAPPOIDEA De Haan, 1833
Family CALAPPIDAE de Haan, 1833
Calappa capellonis Laurie, Reference Laurie and Herdman1906
(Figure 2B)
Material examined
1 male (40.0 × 35.2 mm2), 20°02.9′N, 86°54.4′E, 41–42 m, coll. K. Silambarasan, 17 October 2019.
Restricted synonymy
Calappa gallus capellonis Laurie, Reference Laurie and Herdman1906, p. 355; Sakai, Reference Sakai1976, p. 131, text fig. 73; Calappa gallus Rathbun, Reference Rathbun1937, p. 214 (part); Calappa capellonis Galil, Reference Galil and Crosnier1997, p. 282, figs. 1c, 4c, 5, 29, 35a; Ng et al., Reference Ng, Guinot and Davie2008, p. 48.
Distribution
India
Tamil Nadu (Jeyabaskaran et al., Reference Jeyabaskaran, Ajmalkhan and Ramaiyan2000; Kathirvel and Gokul, Reference Kathirvel and Gokul2010); Kerala (Kumar et al., Reference Kumar, Sushilkumar and Galil2013).
World distribution: Djibouti, Madagascar, Seychelles, Pakistan, Sri Lanka, Indonesia, New Guinea, Japan, Taiwan, and Australia (Galil, Reference Galil and Crosnier1997).
Remarks
This distinctive species was recorded for the first time on the northeast coast of India. Its large mammilate granules, which are distributed throughout the carapace. It is easily confused with C. gallus, but in C. capellonis, the front is more distinctly cleft, the carapace appears transverse, and the gonopods are differently structured (Galil, Reference Galil and Crosnier1997).
Calappa gallus (Herbst, Reference Herbst1803)
(Figure 2C)
Material examined
1 male (20.2 × 14.0 mm2), 17°46.8′N, 83°28.9′E, 39 m, coll. K. Silambarasan, 16 October 2018.
Restricted synonymy
Cancer gallus Herbst, Reference Herbst1803, p. 46; Calappa gallus Krishnamoorthy, Reference Krishnamoorthy2007, p. 93; Kumar et al., Reference Kumar, Biju Sushil Kumar, Raffi and Ajmalkhan2007, p. 285; Ng et al., Reference Ng, Guinot and Davie2008, p. 48 Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018, p. 31.
Distribution
India
Tamil Nadu (Henderson, Reference Henderson1893; Dev Roy and Nandi, Reference Dev Roy and Bhadra2005; Krishnamoorthy, Reference Krishnamoorthy2007); Kerala (Kumar et al., Reference Kumar, Biju Sushil Kumar, Raffi and Ajmalkhan2007); Andaman and Nicobar Islands (Dev Roy, Reference Dev Roy2008).
World distribution
The Red Sea, Gulf of Aden, Seychelles, Madagascar, South Africa, Persian Gulf, Japan, Taiwan, South China, the Philippines, Indonesia (Galil, Reference Galil and Crosnier1997; Ng et al., Reference Ng, Guinot and Davie2008).
Remarks
Calappa gallus resembles Calappa undulata and C. capellonis but they can be differentiated by some distinct features: relative length and breadth of the carapace; prominence of the dorsal tubercles; four rostral teeth; and almost developed lateral teeth (Galil, Reference Galil and Crosnier1997). Our specimen agrees in all respects with these characters. It is a new record for the northeast coast of India.
Calappa exanthematosa Alcock & Anderson, 1894
(Figure 2D)
Material examined
2 male (63.0 × 86.0 mm2), 2 female (91.0 × 122.0 mm2), 16°51.1′N, 82°36.2′E, 117–127 m, coll. K. Silambarasan, 24 November 2020.
Restricted synonymy
Calappa exanthematosa Alcock and Anderson, Reference Alcock and Anderson1894b, p. 177; Alcock and Anderson, Reference Alcock and Anderson1895, pl. 15, fig. 1 & 1a; Kathirvel et al., Reference Kathirvel, Gokul and Thirumilu2007, p. 150; Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018, p. 31.
Distribution
India
Gujarat (Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018); Maharashtra (Ng et al., Reference Ng, Lai, Ghotbeddin and Safaie2011); Kerala (Kumar et al., Reference Kumar, Sushilkumar and Galil2013); Tamil Nadu (Alcock and Anderson, Reference Alcock and Anderson1894b; Krishnamoorthy, Reference Krishnamoorthy2009); Andhra Pradesh (Alcock and Anderson, Reference Alcock and Anderson1894b). Most recently, it was first recorded from the northeast coast of India at a collection depth of around 127 m.
World distribution
The Red Sea, South Yemen, Kenya, South Africa, Pakistan, Taiwan, Japan, and Australia (Galil, Reference Galil and Crosnier1997; Ng et al., Reference Ng, Lai, Ghotbeddin and Safaie2011).
Remarks
The present specimens agree with the original description and the colouration described by Ng et al. (Reference Ng, Lai, Ghotbeddin and Safaie2011) with the following remarks:
(1) C. exanthematosa resembles Calappa japonica but can be differentiated by distinct characteristics, including live colouration, carapace shape, shape of lateral teeth, ventral margin of the chela, and male abdominal somite. The dorsal carapace surface colouration of both C. japonica and C. exanthematosa features yellow tubercles surrounded by maroon spots; however, the pattern of these spots differs slightly on the posterior region of carapace. In C. japonica, the maroon spots are semi-reticulated, while in C. exanthematosa, the spots are rounded.
(2) The shape of the lateral teeth of the carapace differs between the two species. In C. japonica, the lateral teeth are elongated with a curved tip, whereas in C. exanthematosa, the lateral teeth are triangular, with the tip level with the rest of the tooth.
The species was originally described from the Bay of Bengal (deeper waters of Chennai), subsequently, it was recorded from the Iranian coast of the Gulf of Oman, Pakistan, and Mumbai, India (Ng et al., Reference Ng, Lai, Ghotbeddin and Safaie2011).
Calappa clypeata Borradaile, Reference Borradaile and Gardiner1903
(Figure 2E)
Material examined
1 male (20.7 × 32.0 mm2), 18°14.6′N, 84°09.2′E, 33–38 m, coll. K. Silambarasan, 14 November 2020.
Restricted synonymy
Calappa pustulosa var. clypeata Borradaile, Reference Borradaile and Gardiner1903, p. 436; Calappa terrareginae Ng et al., Reference Ng, Lai and Aungtonya2002, p. 344; Calappa clypeata Ng et al., Reference Ng, Guinot and Davie2008, p. 48; Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018, p. 31.
Distribution
India
Tamil Nadu (Krishnamoorthy, Reference Krishnamoorthy2009; Lakshmi Pillai et al., Reference Lakshmi Pillai, Kizhakudanan and Thirumilu2013), this marks the first record of the species on the northeast coast of India.
World distribution
Zanzibar, Seychelles, Madagascar, Maldives, Burma, the western Malay Peninsula, Korea, Japan, China, the Philippines, the South China Sea, Thailand, Indonesia, Australia, and New Caledonia (Ng et al., Reference Ng, Lai and Aungtonya2002, Reference Ng, Guinot and Davie2008).
Remarks
According to Borradaile (Reference Borradaile and Gardiner1903), C. clypeata is similar to the Calappa pustulosa but differs in having denticulate anterolateral edges and clypeiform expansions. Additionally, while the carapace of C. clypeata is smooth and glabrous, C. pustulosa is characterized by its smooth yet more prominently convex carapace, highlighting a subtle but distinct morphological difference. In our specimen, the carapace is greenish-yellow in colour with large pinkish patches. Comparatively, specimens from Australian and Pacific waters reported by Galil (Reference Galil and Crosnier1997) have more pinkish carapace colouration. These variations in colour patterns are likely due to geographical differences and climatic conditions, as supported by Ng et al. (Reference Ng, Lai and Aungtonya2002). This is a rare species on the northeast coast of India, observed on the Shantapalli reefs along the Visakhapatnam coast.
Superfamily LEUCOSIOIDEA Samouelle, 1819
Family LEUCOSIIDAE Samouelle, 1819
Leucosia anatum (Herbst, 1783)
(Figure 2F)
Material examined
3 male (19.2 × 20.3 mm2) and 1 female (18.6 × 21.1 mm2), 20°00.4′N, 86°39.8′E, 34–38 m, coll. K. Silambarasan, 16 October 2019.
Restricted synonymy
Cancer anatum Herbst, Reference Herbst1785, p. 93; Leucosia anatum Tyndale-Biscoe and George, Reference Tyndale-Biscoe and George1962, p. 80, pl. 3, figs. 1, 2, 5, 6; Krishnamoorthy, Reference Krishnamoorthy2007, p. 94; Ng et al., Reference Ng, Guinot and Davie2008, p. 95; Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018, p. 47.
Distribution
India
Maharashtra (Chhapgar, Reference Chhapgar1969); Tamil Nadu (Jeyabaskaran et al., Reference Jeyabaskaran, Ajmalkhan and Ramaiyan2000; Krishnamoorthy, Reference Krishnamoorthy2007); Andhra Pradesh (Dev Roy and Nandi, Reference Dev Roy and Nandi2007b); and West Bengal (Chopra, Reference Chopra1933), now first report from the northeast coast of India.
World distribution
Pakistan, Indonesia, the Philippines, and Malaysia (Kazmi and Tirmizi, Reference Kazmi and Tirmizi1990; Galil, Reference Galil2003).
Remarks
The colour pattern of this species is variable, and thus the species has a polytypic nature (Kazmi and Tirmizi, Reference Kazmi and Tirmizi1990). Hill (Reference Hill, Morton and Tseng1982) suggested that some of the colour morphs of this species are allopatric and others are sympatric. This species has been previously listed from Mumbai (Chhapgar, Reference Chhapgar1969), Gulf of Mannar (Jeyabaskaran et al., Reference Jeyabaskaran, Ajmalkhan and Ramaiyan2000); and Andaman and Nicobar Islands (Alcock, Reference Alcock1896; Dev Roy and Nandi, Reference Dev Roy and Nandi2012).
Seulocia vittata (Stimpson, Reference Stimpson1858)
(Figure 3A)
Material examined
1 male (20.3 × 30.0 mm2), 20°05.6′N, 86°50.6′E, 38–39 m, coll. K. Silambarasan, 16 October 2019.
Figure 3. (A) Seulocia vittata (Stimpson, Reference Stimpson1858) 1 male (20.3 × 30.0 mm2), (B) Naxioides taurus (Pocock, Reference Pocock1890) 1 male (14.0 × 22.0 mm2), (C) Phalangipus hystrix (Miers, Reference Miers1886) 1 male (21.0 × 26.0 mm2), (D) Cryptopodia fornicata (Fabricius, 1787) female (35.2 × 28.3 mm2), (E) Jonas kalpakkamensis (Bharathkumar et al., 2016) male (12.0 × 23.1 mm2), and (F) Charybdis (Charybdis) granulata (De Haan, 1833) female (60.0 × 38.0 mm2).
Restricted synonymy
Cancer craniolaris Herbst, Reference Herbst1785, p. 90, pl. 2, fig. 17; Leucosia craniolaris Fabricius, Reference Fabricius1798, p. 350 (part); Alcock, Reference Alcock1896, p. 232; Seulocia vittata Galil, Reference Galil2005, p. 54; Ng et al., Reference Ng, Guinot and Davie2008, p. 95.
Distribution
India
Maharashtra (Chhapgar, Reference Chhapgar1969); Tamil Nadu (Galil, Reference Galil2005); Andaman and Nicobar Islands (Alcock, Reference Alcock1895a). It has now been documented for the first time from the northeast coast of India.
World distribution
The species has been recorded from Mauritius, Indonesia, Thailand, Malaysia, Singapore, the Philippines and China (Galil, Reference Galil2005; Ng et al., Reference Ng, Guinot and Davie2008).
Remarks
The present specimen agrees with the original description given by Galil (Reference Galil2005) and the colouration described by Prakash and Kumar (Reference Prakash and Kumar2020). Galil (Reference Galil2005) described the original specimens with the following characteristics:
(1) The frontal margin is tri-denticulate, the minute granules are covered on the male abdomen, and the last pereiopodal merus is granulated.
(2) The carapace has a bluish-grey colour, and the posterior region of the carapace is reddish. Two oblique bands are not visible on the carapace.
(3) The anterior and posterior regions of the merus, carpus and propodus of the chelipeds are reddish in colour; the dactylus is reddish, and the tip is whitish.
Superfamily INACHINAE MacLeay, 1838
Family EPIALTIDAE MacLeay, 1838
Naxioides taurus (Pocock, Reference Pocock1890)
(Figure 3B)
Materials examined
1 male (14.0 × 22.0 mm2), 20°00.4′N, 86°39.8′E, 34–38 m, coll. K. Silambarasan, 16 October 2019.
Restricted synonymy
Naxia taurus Pocock, Reference Pocock1890: 77 (type locality: South China Sea); Henderson, Reference Henderson1893: 346; Alcock, Reference Alcock1895b: 219; Griffin, Reference Griffin1966: 270; Sakai, Reference Sakai1976: 218, pl. 74, fig. 1; Naxioides taurus Griffin & Tranter, Reference Griffin and Tranter1986: 171, figs. 37e, f, pl. 11; Davie, Reference Davie2002: 326; Ng et al., Reference Ng, Guinot and Davie2008: 104.
Distribution
India
N. taurus is a new record for Mainland of the Indian coasts. Previously, the species was recorded from the Andaman and Nicobar Islands (Alcock, Reference Alcock1895a; Dev Roy and Nandi, Reference Dev Roy and Nandi2012), as well as from Karmatang and Mayabunder (Kumaralingam et al., Reference Kumaralingam, Raghunathan, Ajithkumar and Chandra2017).
World distribution
Japan, Andaman Sea, Ternate, and the Philippines (Griffin and Tranter, Reference Griffin and Tranter1986).
Remarks
In our study, a specimen was collected that closely resembled the Japanese material figured by Sakai (Reference Sakai1976). However, there were distinct differences: the ambulatory legs were slender; the merus had an acute sub-distal spine; and the dactylus featured spinules along the inner border, which were proportionally shorter. Naxioides taurus shares similarities with Naxioides mamilata but it can be distinguished by several key features, including relatively longer spines, longer ambulatory legs, and shorter rostral spines. Additionally, the upper borders of the merus on the first and second ambulatory legs bear longer distal spines.
Phalangipus hystrix (Miers, Reference Miers1886)
(Figure 3C)
Materials examined
1 male (21.0 × 26.0 mm2), 16°54.7′N, 82°30.2′E, 41 m, coll. K. Silambarasan, 28 June 2019.
Restricted synonymy
Naxia hystrix Miers, Reference Miers1886, p. 60, pl. 6, fig. 4; Alcock, Reference Alcock1895a, p. 220; Phalangipus hystrix Griffin and Tranter, Reference Griffin and Tranter1986, p. 174; Ng et al., Reference Ng, Wang, Ho and Shih2001, p. 13; Ng et al., Reference Ng, Guinot and Davie2008, p. 105; Poore et al., Reference Poore, McCallum and Taylor2008, p. 57, fig.
Distribution
India
Tamil Nadu (Jeyabaskaran et al., Reference Jeyabaskaran, Ajmalkhan and Ramaiyan2000; Krishnamoorthy, Reference Krishnamoorthy2007); and Andaman and Nicobar Islands (Alcock, Reference Alcock1895a).
World distribution
The Red Sea, East Arabian Sea, Sri Lanka, Japan, East China Sea, Taiwan, China, the Philippines, Borneo, Indonesia, north-western Australia (Griffin, Reference Griffin1973; Ng et al., Reference Ng, Guinot and Davie2008).
Remarks
Griffin (Reference Griffin1973) provided a detailed taxonomy of this species. It is widely distributed in the Indo-Pacific and has previously been recorded from various localities along the Indian coasts (Griffin, Reference Griffin1973; Krishnamoorthy, Reference Krishnamoorthy2007; Kathirvel, Reference Kathirvel2008).
Superfamily PARTHENOPOIDEA MacLeay, 1838
Family PARTHENOPIDAE MacLeay, 1838
Cryptopodia fornicata (Fabricius, 1787)
(Figure 3D)
Materials examined
1 female (35.2 × 28.3 mm2), 21°00.4′N, 87°33.0′E, 32–33 m, coll. K. Silambarasan, 19 March 2020.
Restricted synonymy
Parthenope (Cryptopodis) fornicata De Haan, Reference de Haan and von Siebold1833–1850, p. 90, pl. 20, fig. 2, 2a; Alcock, Reference Alcock1895a, p. 282; Cryptopodia fornicata Ng and Davie, Reference Ng and Davie2002, p. 372; Ng et al., Reference Ng, Guinot and Davie2008, p. 130.
Distribution
India
Tamil Nadu (Alcock, Reference Alcock1895a; Krishnamoorthy, Reference Krishnamoorthy2007; Ravichandran et al., Reference Ravichandran, Anbuchezhian, Sivasubramaniyan and Rameshkumar2010); Andaman and Nicobar Islands (Alcock, Reference Alcock1895a).
World distribution
Indo-West Pacific, Central Indian Ocean, South China Sea and Japan (Chiong and Ng, Reference Chiong and Ng1998).
Remarks
The species was previously recorded from various locations along the Indian coasts (Alcock, Reference Alcock1895a). The present specimen closely matches the description provided by Chiong and Ng (Reference Chiong and Ng1998). In our specimen, the carapace is broader than long and pentagonal, with large lateral expansions completely conceal the ambulatory legs, which extend posteriorly beyond the base of the abdomen. The chelipeds are stout and asymmetrical. The merus is flat, with wing-like expansion at the distal end; both upper and lower margins are denticulated, and the upper margins of meri features 3 teeth. A row of granules runs the entire length, separating the anterior and posterior facts of merus. The ambulatory legs are slender, decreasing in length from front to rear, and the dactylus is straight without setae.
Superfamily CORYSTOIDEA, Samouelle, 1819
Family CORYSTIDAE Samouelle, 1819
Jonas kalpakkamensis Bharathkumar et al., 2016
(Figure 3E)
Materials examined
4 male (12.0 × 23.1 mm2), 3 female (18.1 × 25.2 mm2), 17°56.9′N, 83°45.0′E, 36 m, coll. K. Silambarasan, 21 February 2018.
Synonyms
Jonas kalpakkamensis Bharathkumar et al., 2016, p. 481, figs. 2–4A–I.
Distribution
India
Gujarat (Sureandiran et al., Reference Sureandiran, Dave, Suyani and Karuppasamy2024); and Tamil Nadu (Barathkumar et al., Reference Barathkumar, Das and Satpathy2016).
World distribution
Western Indian Ocean (Sureandiran et al., Reference Sureandiran, Dave, Suyani and Karuppasamy2024).
Remarks
Jonas kalpakkamensis and Jonas formosae are closely related species that can be distinguished by differences in their morphological features. One key distinction is that J. kalpakkamensis has three spines on the ventro-basal margin of the merus of the last ambulatory leg, while J. formosae has only one. Additionally, the G1 structure in these species differs: in J. kalpakkamensis, the basal portion is elongated, whereas in J. formosae, it is curved (Ng et al., Reference Ng, Chan and Wang2000). Previously the species was recorded from Kalpakkam coastal waters, southeast coast of India (Barathkumar et al., Reference Barathkumar, Das and Satpathy2016).
Superfamily PORTUNOIDEA Rafinesque, 1815
Family PORTUNIDAE
Charybdis (Charybdis) granulata (De Haan, 1833)
(Figure 3F)
Materials examined
1 female (60.0 × 38.0 mm2), 17°57.4′N, 83°28.1′E, 59 m, coll. K. Silambarasan, 25 October 2018.
Restricted synonymy
Portunus (Charybdis) granulatus de Haan, Reference de Haan and von Siebold1833–1850, pl. 1: 1, Charybdis beauforti Leene & Buitendijk, Reference Leene and Buitendijk1949, p. 293, figs. 2, 4b Charybdis granulata Poore, Reference Poore2004, p. 424, figs. 135c, 137k; Charybdis (Charybdis) granulate Ng et al., Reference Ng, Guinot and Davie2008, p. 153.
Distribution
India
Maharashtra (Aravindakshan and Karbhari, Reference Aravindakshan and Karbhari1985), Tamil Nadu (Dev Roy and Nandi, Reference Dev Roy and Nandi2007a). It is now documented for the first time on the northeast coast of India.
World distribution
The species has been reported from South Africa, Japan, Taiwan, Hong Kong, Singapore, and Australia (Poore, Reference Poore2004).
Remarks
This species is regarded by many as synonymous with the Charybdis (Charybdis) natator. The present specimen agrees with the description given by Wee and Ng (Reference Wee and Ng1995). The dorsal surface of its convex carapace is covered with a dense layer of fine, short setae (dense pile). Frontal ridges are short and granular. Six anterolateral teeth, first to fifth stout, increasing in size from front to rear. The outer borders of each tooth are convex and form an acute tip with an anterior border. The sixth tooth is smallest and narrowest, not more prominent than the preceding teeth. The basal antennal segment is short, excluding the flagellum from the orbit, bearing a low granular outer border of each tooth convex, and forms an acute tip with the anterior border.
Superfamily PORTUNOIDEA Rafinesque, 1815
Family PORTUNIDAE
Lupocyclus philippinensis Semper, Reference Semper and Nauck1880
(Figure 4A)
Materials examined
1 male specimen (18.2 × 15.1 mm2) and 1 female specimen (19.0 × 17.0 mm2), 17°45.8′N, 83°33.5′E, 47–48 m, coll. K. Silambarasan, 12 October 2019.
Figure 4. (A) Lupocyclus philippinensis (Semper, Reference Semper and Nauck1880) male (18.2 × 15.1 mm2), (B) Libystes edwardsi (Alcock, Reference Alcock1900) female (19.2 × 12.1 mm2), (C) Atergatis ocyroe (Herbst, 1801) 1 female (38.0–26.0 mm2), (D) Atergatis integerrimus (Lamarck, Reference Lamarck1818) female (96.0–61.0 mm2), (E) Actumnus squamosus (De Haan, 1835) male (55.0 × 40.0 mm2), and (F) Sphaerozius nitidus (Stimpson, Reference Stimpson1858) 1 male (17.0 × 13.1 mm2).
Restricted synonymy
Lupocyclus philippinensis Semper, Reference Semper and Nauck1880, p. 68; Apel and Spiridonov, Reference Apel and Spiridonov1998, p. 277; Davie, Reference Davie2002, p. 463; Ng et al., Reference Ng, Guinot and Davie2008, p. 151; Poore et al., Reference Poore, McCallum and Taylor2008, p. 68.
Distribution
India: Maharashtra, Goa, Lakshadweep Islands, Tamil Nadu, and Andaman and Nicobar Islands (Alcock, Reference Alcock1899a, Reference Alcock1899b). It is now newly recorded from the northeast coast of India.
World distribution: The species has been recorded from Madagascar, Seychelles, Pakistan, Bay of Bengal, Thailand, Japan, Taiwan, China, South China Sea, the Philippines, Indonesia, Australia, Futuna Islands (Borradaile, Reference Borradaile and Gardiner1902).
Remarks
The present specimen closely agrees with the description provided by Leene (Reference Leene1940). In our specimen, the carapace is slightly broader and sub-circular, covered with a short pile and patches of microgranules and hardly elevated granular patches on the frontal region. Six spiniform teeth form the anterior lateral border, with the first tooth being the largest in comparison to the others. Chelipeds are elongate more than three times their carapace length; they have merus with 6–7 spines. Swimming legs with posterior border of merus armed with one subdistal spine, propodus is smooth; dactylus has finely spiniform teeth.
Libystes edwardsi Alcock, Reference Alcock1900
(Figure 4B)
Materials examined
10 female (19.2 × 12.1 mm2), 17°44.4′N, 83°29.4′E, 47–46 m, coll. K. Silambarasan, 23 October 2019.
Restricted synonymy
Libystes Milne-Edwards, Reference Milne-Edwards1867, p. 285; Nobili, Reference Nobili1906, p. 297; Alcock, Reference Alcock1900, p. 304–305; Naderloo, Reference Naderloo2017 , p. 189; Spiridonov, Reference Spiridonov2020, p. 140.
Distribution
India
Andaman and Nicobar Islands (Alcock, Reference Alcock1900), this is a new record for the northeast coast of India.
World distribution
The species has been previously reported from the Indo-Pacific region, including the Andaman and Nicobar Islands, Thailand, and the China Sea (Dev Roy, Reference Dev Roy2008; Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018).
Remarks
The present specimen closely aligns with the original description provided by Alcock (Reference Alcock1896), with some slight differences observed. The carapace of L. edwardsi is smooth and convex, featuring well-defined anterolateral margins and a rounded posterior region. The frontal margin is narrow with subtle notches, consistent with the original description. However, the chelipeds in our specimen are robust and symmetrical but exhibit a sparsely granulated surface, differing from the finely granulated surface described by Alcock.
Superfamily XANTHOIDEA MacLeay, 1838
Family XANTHIDAE MacLeay, 1838
Atergatis ocyroe (Herbst, 1801)
(Figure 4C)
Materials examined
1 male (40.0 × 29.0 mm2), 1 female (38.0–26.0 mm2), 17°69.6′N, 83°30.2′E, 34–38 m, coll. K. Silambarasan 20 October 2017.
Restricted synonymy: Cancer ocyroe Herbst, Reference Herbst1803, p. 20, pl. 54, fig. 2; Atergatis compressipes MacLeay, Reference MacLeay1838, p. 59; Atergatis floridus Henderson, Reference Henderson1893, p. 35; Alcock, Reference Alcock1898, p. 98; Atergatis ocyroe Jeyabaskaran et al., Reference Jeyabaskaran, Ajmalkhan and Ramaiyan2000, p. 62, pl. 52; Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018, p. 77.
Distribution
India
Gujarat (Trivedi and Vachhrajani, Reference Trivedi and Vachhrajani2016); Maharashtra (Chhapgar, Reference Chhapgar1957); Tamil Nadu (Jeyabaskaran et al., Reference Jeyabaskaran, Ajmalkhan and Ramaiyan2000); and Andaman and Nicobar Islands (Alcock, Reference Alcock1898). It is now reported for the first time from the northeast coast of India.
World distribution
The species has been previously reported in Madagascar, Pakistan, Sri Lanka, and Thailand (Ng and Davie., Reference Ng and Davie2007).
Remarks
The present specimens well agree with the body colouration and morphological characters described by Ng and Davie (Reference Ng and Davie2007). Dark brown spots and patches present on the carapace were surrounded by a fine white line, and chelipeds, legs, external maxillipeds, sternum, and abdomen were also covered with dark brown spots. Chelipeds legs were black coloured with white tips. A similar kind of colour pattern was observed by Barnard (Reference Barnard1950), who examined the specimen of Atergatis compressipes MacLeay, Reference MacLeay1838, collected from South Africa, which is now synonymized with A. ocyroe (Herbst, 1801). Further, the specimen agreed in body colouration with those examined by Tirmizi and Ghani (Reference Tirmizi and Ghani1996) from Pakistani waters.
Atergatis integerrimus (Lamarck, Reference Lamarck1818)
(Figure 4D)
Materials examined
2 males (60.0 × 51.0 mm2), 1 female (96.0 × 61.0 mm2), 17°49.6′N, 83°30.2′E, 32 m, coll. K. Silambarasan, 20 October 2017.
Restricted synonymy: Cancer integerrimus Lamarck, Reference Lamarck1818, p. 272; Ng et al., Reference Ng, Guinot and Davie2008, p. 205; Krishnamoorthy, Reference Krishnamoorthy2009, p. 25; Beleem et al., Reference Beleem, Yokesh Kumar, Satyanarayana, Venkataraman and Kamboj2014, p. 420; Trivedi and Vachhrajani, Reference Trivedi and Vachhrajani2016, p. 17.
Distribution
India
Gujarat, Maharashtra, Goa, Karnataka (Chhapgar, Reference Chhapgar1957), Tamil Nadu (Jeyabaskaran et al., Reference Jeyabaskaran, Ajmalkhan and Ramaiyan2000), and Andaman and Nicobar Islands (Alcock, Reference Alcock1898).
World distribution
The species has been reported from Mauritius, Zanzibar, Hong Kong, the Philippines, and Japan (Sakai, Reference Sakai1976).
Remarks
A. integerrimus is closely related to Atergatis roseus (Ruppel, 1830), sharing several key characteristics: a carapace that is broader than it is long, with a smooth surface. The anterolateral margin is carinated, and the carapace, chelipeds, and pereiopods are all very smooth. The crest of the anterolateral margin is continuous with the posterolateral margin. The chelipeds are unequal, with a distinct and protruding crest along the superior margin of the palm. The body is brick red in colour, while the fingers of the chelipeds and the spines on the dactylus of the pereiopods, are darker, with white tips and teeth.
Superfamily PILUMNOIDEA Samouelle, 1819
Family PILUMNIDAE Samouelle, 1819
Actumnus squamosus (De Haan, 1835)
(Figure 4E)
Materials examined
1 male (55.0 × 40.0 mm2), 20°02.9′N, 86°54.4′E, 56 m, coll. K. Silambarasan, 17 March 2020.
Restricted synonymy
Cancer (Pilumnus) squamosus De Haan, Reference de Haan and von Siebold1833–1850, p. 50; Pilumnus dehaanii Alcock, Reference Alcock1898, p. 198; Actumnus squamosus Rathbun, Reference Rathbun1910, p. 358; Ho et al., Reference Ho, Yu and Ng2000, p. 116; Ng et al., Reference Ng, Wang, Ho and Shih2001, p. 30 and, Reference Ng, Guinot and Davie2008, p. 140.
Distribution
India: Tamil Nadu (Alcock, Reference Alcock1898) and Andaman and Nicobar Islands (Dev Roy, Reference Dev Roy2015). It is now reported for the first time from the northeast coast of India.
World distribution: The species has been documented in Sri Lanka, Japan, China Sea between Taiwan and Chinese coast, Taiwan, Gulf of Thailand, Singapore, the Philippines, and Australia (Takeda and Komatsu, Reference Takeda and Komatsu2017).
Remarks
The single specimen of this species presents an interesting new record for the northeast coast of India. Actumnus squamosus (De Haan, 1835) closely resembles Actumnus tsurukaii (Takeda and Komatsu, Reference Takeda and Komatsu2017), with the following distinct features: both species of A. squamosus and A. tsurukaii have shallow furrows that split the dorsal surface of the carapace into more flattened sections, with the furrows on A. squamosus being slightly larger and deeper than those on A. tsurukaii. In both chelipeds of A. squamosus, the outer surfaces of the palm and immovable finger are densely covered with closely packed conical granules or tubercles. Actumnus tsurukaii, in comparison, has more sparsely distributed conical granules or tubercles that are noticeably larger in size and more widely scattered across the outer surfaces of both the palms and immovable fingers.
Superfamily ERIPHIOIDEA MacLeay, 1838
Family MENIPPIDAE Ortmann, 1893
Superfamily ERIPHIOIDEA MacLeay, 1838
Family MENIPPIDAE Ortmann, 1893
Sphaerozius nitidus Stimpson, Reference Stimpson1858
(Figure 4F)
Materials examined: 1 male (17.0 × 13.1 mm2), 16°50.6′N, 82°26.8′E, 44–46 m, coll. K. Silambarasan, 28 June 2019.
Restricted synonymy: Sphaerozius nitidus Stimpson, Reference Stimpson1858, p. 35 and 1907, p. 62, pl. 7, fig. 5, 5a; Ng et al., Reference Ng, Guinot and Davie2008, p. 64; Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018, p. 53; Sphaerozius nudus Balss, Reference Balss1935, p. 46.
Distribution
India
Maharashtra (Chhapgar, Reference Chhapgar1969) and Tamil Nadu (Kathirvel and Gokul, Reference Kathirvel and Gokul2010). Now it is first reported from the northeast coast of India.
World distribution
The species has been reported from the Red Sea, Madagascar, South Africa, Gulf of Thailand, Hong Kong, Japan, and Korea (Sakai, Reference Sakai1976).
Remarks
This so-called ‘Luster round crab’ is a widespread species in the Indo-West Pacific. Ramadan and Dowidar (Reference Ramadan and Dowidar1972) have remarked that the place where Sphaerozius nitidus was collected is the biofouling area. Similarly, Clark et al. (Reference Clark, Ng, Fransen, McLaughlin, Dworschak and Baba2008) opined that this is a well-known species associated with biofouling organisms, preferring areas with relatively fast-flowing waters. Now the species was collected from the empty shell of a barnacle, i.e. this species is living in the fouling areas, where it can heavily prey on live barnacles. After preying and emptying the shell, it occupies a home, probably to escape from its predators.
Superfamily CARPILIOIDEA Orthman, 1893
Family CARPIILIDAE
Carpilius maculatus (Linnaeus, Reference Linnaeus1758)
(Figure 5A)
Material examined
1 male (62.0 × 45.0 mm2), 17°49.6′N, 83°30.2′E, 38 m, coll. K. Silambarasan, 17 October 2019.
Figure 5. (A) Carpilius maculatus (Linnaeus, Reference Linnaeus1758) 1 male (62.0–45.0 mm), (B) Eucrate alcocki (Serene & Lohavanijaya, 1973) male (15.0–10.0 mm), and (C) Eucrate indica (Castro & Ng, Reference Castro and Ng2010) female (19.0–15.0 mm).
Restricted synonymy
Cancer maculatus Linnaeus, Reference Linnaeus1758, p. 626; Carpilius maculatus Milne Edwards, Reference Milne Edwards1834, p. 382; Ng et al., Reference Ng, Guinot and Davie2008, p. 54; Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018, p. 32.
Distribution
India
Goa (Dev Roy, Reference Dev Roy2008); Tamil Nadu (Jeyabaskaran et al., Reference Jeyabaskaran, Ajmalkhan and Ramaiyan2000; Kathirvel and Gokul, Reference Kathirvel and Gokul2010), and Andaman and Nicobar Islands (Alcock, Reference Alcock1898; Kumaralingam et al., Reference Kumaralingam, Raghunathan, Ajithkumar and Chandra2017).
World distribution: The species were previously reported in the Red Sea, Kenya, Mozambique, South Africa, Madagascar, Mauritius, Indonesia Japan, Taiwan, China, the Philippines, Palau, Australia, Hawaii, Line Islands, Tahiti, and Tuamotu Archipelago (Karaiathil et al., Reference Karaiathil, Raffi, Ajmalkhan and Kannan2002).
Remarks
This so-called ‘spotted reef crab’ is a widespread species in the Indo-Pacific, from the Cocos Islands to French Polynesia and Hawaii (Ng, Reference Ng, Carpenter and Niem1998). Carapace with not less than 11 large roundish dark-red blots disposed as follows: two on either side immediately behind the eye, the smaller and anterior one of these involving the orbital margin; three in a transverse curve across the middle of the carapace; four in another transverse line just in front of the posterior margin.
Superfamily GONEPLACOIDEA MacLeay, 1838
Family EURYPLACIDAE Stimpson, 1871
Eucrate alcocki Serene & Lohavanijaya, 1973
(Figure 5B)
Material examined
1 male (15.0 × 10.0 mm2), 1 female (20.0 × 17.0 mm2), 17°42.7′N, 83°32.4′E, 52–53 m, coll. K. Silambarasan, 29 October 2019.
Restricted synonymy
Eucrate crenata var. dentata Alcock, Reference Alcock1900, p. 301; Sankarankutty, Reference Sankarankutty1966, p. 350; Eucrate alcocki Serène, in Serène and Lohavanijaya, 1973, p. 71, pl. 16, fig. B–C; Eucrate alcocki Jeyabaskaran et al., Reference Jeyabaskaran, Ajmalkhan and Ramaiyan2000, p. 83; Ng & Davie, Reference Ng and Davie2002, p. 378.
Distribution
India
Gujarat (Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018) and Tamil Nadu (Jeyabaskaran et al., Reference Jeyabaskaran, Ajmalkhan and Ramaiyan2000; Silambarasan et al., Reference Silambarasan, Sujatha, Rajalakshmi and Sundaramanickam2017). It is now reported for the first time from the northeast coast of India.
World distribution
The species has been reported from Vietnam (Serène and Lohavanijaya, Reference Serene and Lohavanuaya1973).
Remarks
The taxonomy of E. alcocki was clarified by Castro and Ng (Reference Castro and Ng2010). Eucrate alcocki bears a resemblance to Eucrate. formosensis, Eucrate indica, and Eucrate sexdentata, with the following distinct characteristics: the carapace is relatively long; the anterolateral margin is armed with two teeth, excluding the external orbital tooth; the second tooth is acutely triangular; the last tooth is rudimentary; the fissures on the dorsal orbital margin are indistinct; the first pleopod has a slender distal portion and is armed with spines on both sides with the apex slightly expanded. Varying numbers of large irregular red-brown spots covered the carapace, along with smaller anterior spots or dots. The anterior spots vary from medium-sized spots that decrease in size anteriorly to many spots of evenly small size.
Eucrate indica Castro & Ng, Reference Castro and Ng2010
(Figure 5C)
Material examined
1 female (19.0–15.0 mm2), 17°44.4′N/83°29.4′E, 47–46 m, coll. K. Silambarasan, 23 October 2019.
Restricted synonymy
Eucrate crenata var. dentata Alcock, Reference Alcock1900, p. 301; Sankarankutty, Reference Sankarankutty1966, p. 350; Eucrate alcocki Serène, in Serène and Lohavanijaya, 1973, p. 71, pl. 16, fig. B–C; Eucrate alcocki Jeyabaskaran et al., Reference Jeyabaskaran, Ajmalkhan and Ramaiyan2000, p. 83; Ng & Davie, Reference Ng and Davie2002, p. 378.
Distribution
India
Tamil Nadu (Castro & Ng, Reference Castro and Ng2010; Silambarasan et al., Reference Silambarasan, Sujatha, Rajalakshmi and Sundaramanickam2017). It is now reported for the first time from the northeast coast of India.
World distribution
The species has been reported in Vietnam (Serène and Lohavanijaya, Reference Serene and Lohavanuaya1973).
Remarks
The morphological and colour patterns of E. indica have the distinct characteristics of anterolateral margins armed with two teeth, excluding the external orbital tooth; the second tooth is acutely triangular; and the third anterolateral tooth is large and sharp. The carapace has relatively long posterolateral borders. The fifth pereiopod propodus is slender; there are eight irregular, large, red-brown spots on the median portion of the dorsal surface of the carapace, each flanked by two smaller, vertically placed spots. Small red-brown spots are covered along the anterior border of the carapace and dorsal surface of chelipeds, which are clear diagnostic characters of the species (Castro and Ng, Reference Castro and Ng2010). Our specimen agrees in all respects with these characters.
General discussion
During the present study, 81 species of brachyuran crabs belonging to 19 families and 46 genera were recorded (Table 1). Of these, the family Portunidae has the greatest number of species (24 sp.), followed by Leucosiidae (12 sp.) and Xanthidae (5 sp.), with the other families representing one to five species of each. Of which, 21 species were newly recorded from the northeast coast of India: viz., Calappa capellonis, Calappa gallus, Calappa exanthematosa, Calappa clypeata (Calappidae); Carpilius maculates (Carpilidae); Jonas kalpakkemensis (Corystidae); Dorippe frascone (Dorippidae); Naxioides taurus , Phalangipus hystrix (Epialtidae); Eucrate indica, Eucrate alcocki (Euryplacidae); Leucosia anatum, Seulocia vittata (Leucosiidae); Sphaerozius nitidus (Menippidae); Cryptopodia fornicata (Parthenopidae); Actumnus squamosus (Pilumnidae); Charybdis granulata, Libystes edwardsi, Lupocyclus philippinesis (Portunidae); Atergatis integerrimus, Atergatis ocyroe (Xanthidae); and one is also a new record of the mainland coast of India.
In recent years, biodiversity studies have gained significant attention not only due to the global reduction in flora and fauna but also as a response to habitat degradation, climate change, and increasing human exploitation of natural resources. These factors have heightened the urgency to document and conserve biodiversity. Reporting the appearance of rare or previously unrecorded species is essential to update the national biodiversity database and understand species distribution patterns. The northeast coast of India has a wide diversity of brachyuran crab faunal resources, particularly in Sandheads and Visakhapatnam coast. Muddy bottoms, soft shells, coral reefs, rocky patches, and rocky out crops are the key features of these habitats which provide support for the rich crustacean and finfish resources (Silambarasan et al., Reference Silambarasan, Kar, Prasad, Pattnayak and Ramalingam2022). Moreover, a significant limitation of the present study was the inadequate coverage of exploratory trawl surveys, which restricted detailed investigation of brachyuran crabs along the northeast coast of India. Despite this constraint, the study successfully documented several previously unrecorded brachyuran crab species. These findings highlight the need for more comprehensive surveys to better understand the crustacean diversity of the region. Expanding the knowledge of species distributions will contribute to improved biodiversity documentation, which is essential for future monitoring and effective management practices.
Data
The data are not publicly accessible; it can still be requested under specific conditions.
Acknowledgements
We would like to express our sincere gratitude to the Director General, Fishery Survey of India, Govt. of India, Ministry of Fisheries, Animal Husbandry and Dairying for granting the necessary permission and providing the facilities required for this work. We also extend our sincere thanks to the Skipper and all crew members of the vessels MFV Matsya Shikari and MFV Matsya Darshini for their invaluable assistance and cooperation in sample collection during the survey cruises. Additionally, we are deeply grateful to Dr M. Kathirvel, Former Principal Scientist, ICAR-Central Institute of Brackish Water Aquaculture, Chennai for his insightful comments and suggestions to improve the manuscript.
Author contributions
Krishnan Silambarasan: writing and reviewing, and sample collection and identification, conceptualization, and analysis; Annada Bhusan Kar: conceptualization, writing and reviewing, and supervision; G. V. A. Prasad: supervision, sample collection, and identification; S. K. Pattnayak: writing and reviewing; R. Jeyabaskaran: supervision, writing, and reviewing.
Financial support
This research has not received any specific grant from an external funding agency.
Competing interests
None.
