Introduction
The crabs occupy a significant position among the animal groups of the marine environment (Sureandiran et al., Reference Sureandiran, Dave, Suyani, Karuppasamy and Vidhya2023a). Among the class Malacostraca the brachyuran crabs display high diversity which constitutes 107 families, 1567 genera with 7683 valid species (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). In India, a total of 910 species of marine brachyuran crabs under 361 genera belonging to 62 families were reported (Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018). The brachyuran crabs of the family Corystidae is commonly called as the burrowing crab because they mostly show the character of burrowing under the soft sediments and are mostly found in the sandy or muddy environment (Naderloo, Reference Naderloo2017). The burrowing crabs are commonly distributed in the global waters at a depth of less than 115 m (Marco-Herrero, Reference Marco-Herrero2022). Globally, the corystid group consists of 11 genera among those the genus Jonas commonly called as the sand crab comprises of 7 valid species (DecaNet, 2024). In India three species namely J. choprai, J. indicus, and J. kalpakkamensis were reported from coastal waters of Tamil Nadu and West Bengal (Chopra, Reference Chopra1935; Deb, Reference Deb1999; Manokaran et al., Reference Manokaran, Ajmal Khan, Lyla and Murugan2008; Pillai and Thirumilu, Reference Pillai and Thirumilu2008; Barathkumar et al., Reference Barathkumar, Das and Satpathy2016).
Jonas kalpakkamensis was documented only from Tamil Nadu coast along the Bay of Bengal region further there is no record of this species from any other coast. In the present study, the sand crab, J. kalpakkamensis Barathkumar, Das & Satpathy, Reference Barathkumar, Das and Satpathy2016 is reported for the first time from the Gujarat coast along the Western Indian Ocean. Further, detailed taxonomical notes of the species and identification key for Jonas spp. are provided.
Materials and methods
A total of five specimens (n = 5) were collected from the crustacean bycatch landings during March 2023 from Veraval fishing harbour (20° 50’ N and 70° 28’ E), Gujarat, India, Western Indian Ocean (Figure 1). The specimens of J. kalpakkamensis were caught by trawl net operated along the Gujarat coast, Arabian Sea at a depth range between 15 and 50 m. The collected sand crab specimens were identified following Barathkumar et al. (Reference Barathkumar, Das and Satpathy2016) and morphometric measurements (Table 1) were made using the Vernier caliper (VC) with an accuracy of 0.1 mm. Photographs of the crabs were captured using the Nikon D-5300 camera and further, the crabs were preserved using 10% formalin and deposited in the Museum of College of Fisheries Science, Veraval. In the present study, body parts of the sand crab were made using the pencil sketch manner by referring the standard literature and software (Barathkumar et al., Reference Barathkumar, Das and Satpathy2016; Sureandiran et al., Reference Sureandiran, Dave, Solanki, Karuppasamy, Suyani and Vidhya2023b).
Map of the study area Veraval fishing harbour, Gujarat, Western Indian Ocean (note: red marking indicates the present study area and blue marking indicates the previous report).
Morphometric measurements of Jonas kalpakkamensis collected from the Veraval fishing harbour, Gujarat, Western Indian Ocean and comparison with holotype and paratype (Barathkumar et al., Reference Barathkumar, Das and Satpathy2016)
(‘S’ present study specimens).
Results
Systematic position
Order: DECAPODA Latreille, 1802
Family: CORYSTIDAE Samouelle, 1819
Genus: Jonas Hombron & Jacquinot, 1846
Species: Jonas kalpakkamensis Barathkumar, et al., Reference Barathkumar, Das and Satpathy2016 (Figure 2–4)
Materials examined
Sand crab, J. kalpakkamensis (n = 5), (carapace width = 12.4 to 17.2 mm, carapace length = 19.2 to 30.2 mm); coll. B. Sureandiran; 9th March, 2023 from the Veraval fishing harbour (20° 50’ N and 70° 28’ E), Gujarat, India.
Dorsal and ventral view of Jonas kalpakkamensis Barathkumar, Das & Satpathy, Reference Barathkumar, Das and Satpathy2016 collected from the Veraval fishing harbour, Gujarat, Western Indian Ocean. (scale bars: 1 cm).
Jonas kalpakkamensis: (a) frontal view of carapace, (b) lateral view of carapace, (c) dorsal view of mandible & maxilliped, (d) frontal view of left claw, (e) dorsal view of left claw, (f) male abdomen, (g) female abdomen, (h) dorsal view of G2 and (i) close view of G2 tip.
Jonas kalpakkamensis, (a) Abdomen, (b) 4th ambulatory leg comprising of three spines, (c) G1 and (d) G2 tip (scale bars: a & b - 5 mm, c & d - 1 mm).
Diagnosis
Carapace oval, dorsal surface possessing tiny hair, granules scattered, 10 spines present on lateral margin size reducing towards last spine, 1st larger, 2nd–4th spine equal in size 5th & 6th slightly equal, 7th–9th spine blunt not spinous, 10th spine longer than 9th, between the 10th spine of both lateral side eight to twelve granules present; rostrum bifurcated; supra-orbital spine elongated and longer than size of rostrum; eyes fully occupying orbit portion, orbital portion not developed well, some setae present around orbit portion; orbital spine elongated than first anterolateral tooth of carapace; chelipeds layered with granules, carpus possessing two unequal spines on outer margin, merus size lesser than the ischium; ambulatory legs with dense hairs, fourth leg consists of 3 spines, last leg dactylus spatuliform; abdomen region short, 1st–3rd abdomen somites not wide, 4th & 5th somite extremely wide, 6th somite half wide in size of 5th somite. G1 slender, L-shaped, stout at base, tip elongated.
Colouration
The live specimen carapace region is bright orange reddish with frontal portion more bright than the posterior part; claw shows faded colour in appearance; ambulatory legs tip and hair reddish; 1st five spines on the lateral region of the carapace orange coloured remaining all spines colour faded. The colouration of the 10% formalin preserved specimen was slightly faded on the carapace region compared to the fresh specimen.
Remarks
Jonas kalpakkamensis shows similarity with its congener J. formosae because the J. formosae is the only species found in the Southeast Asia and Northern region of Taiwan (Ng et al., Reference Ng, Chan and Wang2000). The J. formosae is distinguishable from J. kalpakkamensis through scattered tiny granules like structure present over the surface of the carapace region particularly on the raised portion and presence of 3 spines over the merus segment of the walking leg (Barathkumar et al., Reference Barathkumar, Das and Satpathy2016). However J. choprai reported from the Indian coast (Manokaran et al., Reference Manokaran, Ajmal Khan, Lyla and Murugan2008) is differentiated from the J. kalpakkamensis by the presence of wider carapace and elongated supraorbital spines. According to Ng et al. (Reference Ng, Chan and Wang2000) the holotype (ZRC 1969.11.20.3) examined specimen consists of longest 2nd leg and in J. kalpakkamensis all the ambulatory legs are quite similar in size. The another species reported from Indian coast was J. indicus which is differentiated from the J. kalpakkamensis in possessing the well-developed spines (Naderloo, Reference Naderloo2017) referred from the holotype specimen of J. indicus (C 1766/1) in case of J. kalpakkamensis 1st to 4th spine only developed remaining spine are blunt and undefined.
Habitat
Generally, found on the sandy mud shallow habitat with depth range of 20–30 m (Barathkumar et al., Reference Barathkumar, Das and Satpathy2016). In the present study, specimens were caught at the muddy region at a depth range of 15–50 m.
Known distributions
J. kalpakkamensis is reported only from Bay of Bengal (Tamil Nadu) (Barathkumar et al., Reference Barathkumar, Das and Satpathy2016).
Discussions
The corystid group crabs are only reported from the soft sediment areas at the depth range of 2–115 m according to Marco-Herrero (Reference Marco-Herrero2022). In the present study, the specimens of J. kalpakkamensis were harvested at the depth range of 15 to 50 m which confirms the depth of availability and habitat of the species in marine ecosystem. The genus Jonas closely resembles with the genus Gomeza as these genera can be differentiated by having slender and elongated carapace from the anterior to the posterior region in the Jonas, on the other hand the Gomeza genus possess the oval like shaped carapace (Ng et al., Reference Ng, Chan and Wang2000). In India three species under Jonas genus were reported viz. Jonas choprai, J. indicus, and J. kalpakkamensis from the east coast of India and no report is found along the west coast of India (Trivedi et al., Reference Trivedi, Trivedi, Vachhrajani and Ng2018). The J. indicus was earlier reported from the Gulf of Oman region (Barathkumar et al., Reference Barathkumar, Das and Satpathy2016) and this J. indicus is the closely resembling species with J. kalpakkamensis due to the morphological similarity like the presence of the tiny granulations with tubercles in the upper surface region of the carapace referred from the holotype specimen – C 1766/1 collected from the Bay of Bengal at depth range between 36 and 96.5 m. As per IUCN Red List of Threatened Species (IUCN, 2022) the sand crab J. kalpakkamensis was categorized as Not Evaluated (NE) and presently the species is not consumed for food, but it is utilized for preparation of animal feed due to its insect like appearance and very less meat yielding property. The identification of sand crabs under the genus Jonas is quite difficult due to lack of proper taxonomical notes and species descriptions. The comparison of the present study specimens with the holotype specimen (Male, ZSI/MBRC/D1.244) collected from the Chennai coast and paratype specimen (Male, EnSD/2013/35-36) collected from the Chennai coast helped in identification of the specimen as J. kalpakkamensis. In the present study, the specimens were collected during the March month which is considered as the pre-monsoon season along the Gujarat coast. The sand crab existence in the Arabian Sea region could be attributed to changes in the climate, such as fluctuations in sea surface temperature (SST) and the dynamic water circulation pattern between the Arabian Sea and the Bay of Bengal (Sureandiran et al., Reference Sureandiran, Suyani, Tandel and Karuppasamy2023c). Besides exploratory vessel surveys are required in and around the north-eastern Arabian Sea region to estimate the actual diversity of the decapod crustacean resources (Sureandiran et al., Reference Sureandiran, Dave, Suyani and Karuppasamy2024).
Key to the genus Jonas and the list of species reported globally
1. Carapace longitudinally ovate; clusters of pearliform granules present………1
‐ Carapace oval………2
‐ Carapace elongated………3
1a. Lateral margin consists of 7 spines, ambulatory legs with dense hairs………J. macropthalmus
1b. G1 hooked and the distal part sub-conical in shape………J. distincta
1c. G1 L-shaped in ventral view; tip G2 short with broad base, basal part curved………J. kalpakkamensis
1d. G1 hooked and the distal is elongated, tip prolong appears filamentous………J. formosae
2a. First anterolateral spine strong and longer than remaining; presence of distinct ventral spine in basis-ischium of last ambulatory leg………J. choprai
2b. Prominent curved lateral spines; larger posterolateral teeth………J. indicus
3a. Penultimate segment longer, half as long as first………J. leuteanus
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.
Author contributions
B. Sureandiran: collected the crab specimen, preparation of the manuscript, software analysis, microscopic examination and image preparation. T. H. Dave: supervision of the study. N. K. Suyani: review and editing of manuscript. K. Karuppasamy: taxonomic advice and conceptualization.
Financial Support
The study not received fund from any external agency.
Competing interests
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.
