Introduction
The crustaceans hold the 4th position in the case of the highly diversified animal group (Sureandiran et al., Reference Sureandiran, Dave, Suyani, Karuppasamy and Vidhya2023a). In the world, the total estimated number of crustacean species was between 50,000 and 67,000 species which includes the major groups such as shrimp, crab, lobster, etc. (Webber et al., Reference Webber, Fenwick, Bradford-Grieve, Eagar, Buckeridge, Poore and Charleston2010). The infraorder Brachyura commonly called the true crabs is regarded as the rich group among the decapods, with 7683 species belonging to 107 families (De Grave et al., Reference De Grave, Decock, Dekeyzer, Davie, Fransen, Boyko, Poore, Macpherson, Ahyong, Crandall, de Mazancourt, Osawa, Chan, Ng, Lemaitre, van der Meij and Santos2023). The family Goneplacidae shows a wide range of variation in the distribution of the species as they are found from the shallow sub-tidal area to 1300 m in the bathypelagic zone (Castro, Reference Castro2007). These goneplacid crabs consist of 36 valid genera (DecaNet, 2024). The genus Carcinoplax can be differentiated from its family members through transverse rectangular-shaped carapace; rounded sub-orbital border, both consist of a blunt inner tooth that is not visible from the dorsal region (Castro, Reference Castro2007; Ng and Castro, Reference Ng and Castro2007). Globally, the genus Carcinoplax comprises of 45 valid species (DecaNet, 2024). From the Indian coast, six species were reported viz., Carcinoplax fasciata Ng & Kumar, 2016, C. indica Foflein, 1904, C. longimanus (De Haan, 1833), C. longipes (Wood-Mason & Alcock, 1891), C. specularis Rathbun, Reference Rathbun1914 mentioned in the monograph of Trivedi et al. (Reference Trivedi, Trivedi, Vachhrajani and Ng2018) and recently, Ng and Mitra (Reference Ng and Mitra2019) described a new species from the Bay of Bengal C. mistio.
During a regular visit to the Veraval fishing harbour, Gujarat, a single male specimen of Carcinoplax haswelli (Miers, Reference Miers1884) was collected from the trawl bycatch of the crustacean landing. The present study reports the first record of C. haswelli from the Indian coast. Further, detailed taxonomical notes of the species and its global distribution were deliberated.
Materials and methods
On 22 January 2023, a single specimen of goneplacid crab, C. haswelli was collected from the trawl bycatch landing of Veraval fishing harbour (20°50′N and 70°28′E), Gujarat, Northwest coast of India (Figure 1). The specimen was caught through the demersal trawler targeted for the commercial group of crustaceans and the trawler was operated at an actual depth of 30–150 m. The collected specimen was identified as C. haswelli (Figure 2) by referring to taxonomic literatures (Castro, Reference Castro2007; Ng and Mitra, Reference Ng and Mitra2019; Ng and Castro, Reference Ng and Castro2020). The morphometric measurements of the specimen was made using the Vernier caliper with an accuracy of 0.1 mm and the photographs of the crab were captured using the Nikon D-5300 camera. The G1 and G2 images were captured using the Leica microscope. The specimen examined was preserved using 10% formalin (Figures 3 and 4) and deposited in the Museum of the College of Fisheries Science, Veraval, Gujarat, India (KU/COF/CH.1). The abbreviations CW and CL denote carapace width and carapace length, respectively.
Figure 1. Map representation of the study area Veraval fishing harbour, Gujarat, Northwest coast of India, Indian Ocean (note: blue marking indicates the present study area and red marking indicates the previous report globally).
Figure 2. Dorsal view of Goneplacid crab, Carcinoplax haswelli (Miers, Reference Miers1884) (fresh specimen) collected from the Veraval fishing harbour, Gujarat, Northwest coast of India, Indian Ocean.
Figure 3. Dorsal view of Goneplacid crab, Carcinoplax haswelli (Miers, Reference Miers1884) (10% formalin preserved specimen) collected from the Veraval fishing harbour, Gujarat, Northwest coast of India, Indian Ocean.
Figure 4. Ventral view of Goneplacid crab, Carcinoplax haswelli (Miers, Reference Miers1884) (10% formalin preserved specimen) collected from the Veraval fishing harbour, Gujarat, Northwest coast of India, Indian Ocean.
Results
Systematics
Order: Decapoda Latreille, 1802
Family: Goneplacidae MacLeay, 1838
Genus: Carcinoplax H. Milne Edwards, 1852
Species: Carcinoplax haswelli (Miers, Reference Miers1884)
Synonymy
Pseudorhombila vestita var. sexdentata: Miers, Reference Miers1884: 184, 240, pl. 24.
Pseudorhombila haswelli: Miers, Reference Miers1884: 241.
Honoiplax haswelli: Rathbun, Reference Rathbun1914: 146; Tesch, Reference Tesch1918: 190, pl. 10, fig. 1; Serène, Reference Serène1968: 91; Davie, Reference Davie2002: 374; Ng et al., Reference Ng, Guinot and Davie2008: 189; Poore et al., Reference Poore, McCallum and Taylor2008: 73; Ng et al., Reference Ng, Clark and Ahyong2022: 3, fig. 1, 4 fig. 2, 5 fig. 3, 6 fig. 4, 7 fig. 5.
Carcinoplax sinica: Chen, Reference Chen1984: 190, 197, 200, fig. 2, pl. 1, figs. 6, 10; Chen, Reference Chen1998: 270, 310, fig. 3; Dai et al., Reference Dai, Yang, Song and Chen1986: 366, figs. 190–2 to 190–4, pl. 53, fig. 5; Guinot, Reference Guinot and Forest1989: 285–287, figs. 12a–d, 13a, b, 14a, b, pl. 5a–I; Dai and Yang, Reference Dai and Yang1991: 395, figs. 190–2 to 190–4, pl. 53, fig. 5; Hsueh and Huang, Reference Hsueh and Huang2002: 126, figs. 8D; Castro, Reference Castro2007: 610 (list), 625, 639, 640; Ng and Mitra, Reference Ng and Mitra2019: figs. 4, 5, 6 E to H, fig. 7 C, D, E, F, K, L, figs. 8K, M, N, C, figs. 9 E, F, C; Ng and Castro, Reference Ng and Castro2020: 281.
Carcinoplax haswelli: Ng et al., Reference Ng, Clark and Ahyong2022: figs. 1–5.
Material examined
1 Male (KU/COF/CH.1); CW, 35 mm; CL, 24 mm; coll. B. Sureandiran; 22 January 2023, trawl net, 30–150 m depth, Veraval fishing harbour, Gujarat, Northwest coast of India (20°50′N and 70°28′E).
Diagnosis
Carapace diagonally hexagonal; dorsal region of carapace smooth without any markings or spots, lateral surface closely packed, granules rounded; epigastric region short but visible; post-orbital region not well defined; frontal margin plain, smooth, lamellar, shorten, bilobed consists of small median notch, supra-orbital part low, not visible simply, defined by groove, not noticeably projecting on the lateral area; 1st teeth blunt not spinous but long; 2nd teeth also blunt not spinous, long and facing little away from carapace (Figure 5). Dorsal margin of cheliped palm rounded in shape, smooth; carpus mesial margin protruding, tooth low and rounded, lateral margin of carpus consists of a little single spine; merus elongated with low rounded tooth present on distal 1/3rd of dorsal margin (Figure 5). Pleopod 1–5 slender and long; upper region of thoracic sternum enclosed with many small, rounded, closely packed granules; male pleon triangular in shape, lateral margin moderately convex; shape of the telson triangular with unique concave lateral margins (Figure 6). In male, G1 comparatively slender; distal part widening little, laterally flattened; G2 longer than G1, distal part with flagellate-like structure (Figure 7).
Figure 5. Goneplacid crab, Carcinoplax haswelli: (A) frontal view of right chela, (B) frontal view of left chela, (C) frontal view of cephalothorax, (D) dorsal view of right cheliped.
Figure 6. Goneplacid crab, Carcinoplax haswelli: (A) view of left and right third maxilliped, (B) view of the anterior thoracic sternum, pleonal somites, (C) view of male pleon, (D) view of male gonopods (G1 and G2).
Figure 7. Goneplacid crab, Carcinoplax haswelli: (A) microscopic view of left and right G1, (B) microscopic view of left G1 tip, (C) microscopic view of left and right G2.
Colour
Fresh specimen – carapace bright orange, without spots; ambulatory legs tip slightly yellow to white; ventral surface white (Figure 2). Formalin preserved specimen (10%) – pale orange; ambulatory legs pale orange, tip pale yellow; ventral surface white (Figures 3 and 4).
Known distributions
Carcinoplax haswelli previously reported from Gulf of Tonkin, Northern Australia, South China Sea, Taiwan, Western Philippines (Ng et al., Reference Ng, Clark and Ahyong2022) (Figure 1).
Remarks
Macleay (Reference Macleay1838) provided the differentiating character of the genus Carcinoplax from the congeners by slim and flattened upside down G1; sternal suture incomplete 6/7. Guinot (Reference Guinot and Forest1989) mentioned that C. sinica shows contrasting characteristics with C. purpurea more accurately; they can be differentiated by the morphology of the 2nd frontal-lateral tooth which is a hook structure in C. sinica when compared with C. purpurea. Further, the reddish carapace colour pattern in C. sinica makes it to differ from the closest species C. purpurea (Guinot, Reference Guinot and Forest1989). Ng and Mitra (Reference Ng and Mitra2019) recently described a new species, Carcinoplax mistio from the Bay of Bengal region. They stated that C. mistio superficially looks like C. sinica, particularly the transverse-shaped carapace and 2nd prominent front-lateral tooth spiniform and mildly curved; in G1 of C. sinica two-third of distal part is straight and the tip is round and short (Figure 7), on the other hand in C. mistio two-third of distal part is curved and the tip is elongated; this was observed from the holotype male (29.2 × 19.0 mm, ZSI Reg. No. C7123/2). Moreover, the inner angle of the male carpus tooth on the cheliped is longer in C. sinica and shorter in C. mistio. They also stated that crab specimens deposited as C. sinica in the Persian Gulf are C. mistio. As per the re-description work done by Ng et al. (Reference Ng, Clark and Ahyong2022) on Homoioplax haswelli, the genus Homoioplax shares all the characteristics with the genus Carcinoplax; hence, they considered Homoioplax as the junior subjective synonym. While referring to DecaNet (2024) for valid taxonomic status, it was mentioned that H. haswelli is regarded as the synonymised name and the accepted name was C. haswelli and C. sinica was unaccepted and regarded as junior subjective. Ng et al. (Reference Ng, Clark and Ahyong2022) compared the taxonomy characters of C. haswelli and C. sinica and concluded that both species were indistinguishable.
Discussion
The species belonging to the genus Carcinoplax are distributed from the sub-temperate to Indo-West Pacific region (Castro, Reference Castro2009). The present study specimen (KU/COF/CH.1) clearly agrees with the taxonomy characters of the lectotype male specimen (10.2 × 7.3 mm, NHM 1882.7) described from Arafura Sea, Australia (Ng et al., Reference Ng, Clark and Ahyong2022). The goneplacid crab, C. haswelli was listed as Not Evaluated (NE) on the IUCN Red List of Threatened Species (IUCN, 2022). Because of poor appearance and very low meat-yielding of the goneplacid crabs, they are mostly used in the preparation of animal feed rather than for human consumption. The presence of the goneplacid crabs in the fishery is not common; mostly, they are caught through deep-sea trawlers. Because of seasonal fluctuations and temperature variations, C. haswelli may be migrated from the Pacific Ocean to Indian Ocean (Sureandiran et al., Reference Sureandiran, Dave, Solanki, Karuppasamy, Suyani and Vidhya2023b, Reference Sureandiran, Suyani, Tandel and Karuppasamy2023c).
Conclusion
The occurrence of C. haswelli in the Indian coast may be due to the dynamic water circulation pattern between the Indian Ocean and Pacific Ocean, and other physical factors such as water current, salinity gradient, wind pattern, etc., may also lead to the distribution and range extension of this goneplacid crab. The present study observation can be considered as evidence for the presence and distribution of C. haswelli from the Indian Ocean.
Data availability
The authors confirm that the data supporting the findings of this study are available within the article.
Acknowledgements
The authors wish to express their sincere gratitude to the Principal, College of Fisheries Science, Kamdhenu University, Veraval for providing necessary laboratory facilities and support. The authors thank the anonymous reviewers for their valuable comments and suggestions, which helped to improve the quality of the manuscript.
Authors contributions
B. Sureandiran: collected the crab specimen, preparation of the manuscript, software analysis and image preparation. T. H. Dave: supervision of the study. N. K. Suyani: review and editing of manuscript, photography of the crab and microscopic examination. K. Karuppasamy: taxonomic advice and conceptualisation.
Financial support
The study did not receive fund from any external agency.
Competing interest
None.
Ethical standards
The authors declare that the work did not involve experiments with vertebrates. The work was carried out within local guidelines without causing damage to the environment.
