Journal of Threatened Taxa | www.threatenedtaxa.org | 26 June 2026 | 18(6): 29114–29119

ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print)

https://doi.org/10.11609/jott.9612.18.6.29114-29119

#9612 | Received 04 April 2025 | Final received 19 May 2026| Finally accepted 01 June 2026

First record of leucosiid crab Lyphira perplexa Galil, 2009 (Decapoda: Brachyura: Leucosiidae) from the eastern coast of India in West Bengal

Prabir Sahoo ¹ , Sagar Samanta ² , Avik Bhanja ³ , Manas Das ⁴ & Pijush Payra ⁵

¹ Department of Coastal Aquaculture, Centre of Advanced Study in Marine Sciences, Annamalai University, Cuddalore, Tamil Nadu 608502, India.

^2,3,4 Aquaculture Lab, Department of Biological Sciences, Midnapore City College, Paschim Medinipur, West Bengal 721129, India.

⁵ Department of Fisheries Science, Ramnagar College, Depal, Purba Medinipur, West Bengal 721453, India.

¹ prabiraqua29@gmail.com, ² sagarsamanta.aquah@gmail.com, ³ avikbhanja07@gmail.com, ⁴ manasdas3333@gmail.com, ⁵ pijushpayra@gmail.com (corresponding author)

Editor: Anonymity requested. Date of publication: 26 June 2026 (online & print)

Citation: Sahoo, P., S. Samanta, A. Bhanja, M. Das & P. Payra (2026). First record of leucosiid crab Lyphira perplexa Galil, 2009 (Decapoda: Brachyura: Leucosiidae) from the eastern coast of India in West Bengal. Journal of Threatened Taxa 18(6): 29114–29119. https://doi.org/10.11609/jott.9612.18.6.29114-29119

Copyright: © Sahoo et al. 2026. Creative Commons Attribution 4.0 International License. JoTT allows unrestricted use, reproduction, and distribution of this article in any medium by providing adequate credit to the author(s) and the source of publication.

Funding: None.

Competing interests: The authors declare no competing interests.

Author details: Prabir Sahoo—researcher, Department of Coastal Aquaculture, Centre of Advanced Study in Marine Sciences, Annamalai University, Cuddalore, Tamil Nadu 608502, India. Sagar Samanta—student, Aquaculture Lab, Department of Biological Sciences, Midnapore City College, Paschim Medinipur, West Bengal 721129, India. Avik Bhanja—assistant professor, Department of Biological Sciences, Midnapore City College, Paschim Medinipur, West Bengal 721129, India.

Manas Das—assistant professor, Department of Biological Sciences, Midnapore City College, Paschim Medinipur, West Bengal 721129, India. Pijush Payra—faculty, Department of Fisheries Science, Ramnagar College, Depal 721453, Purba Medinipur, West Bengal, India

Author contribution: Prabir Sahoo: Resources, Investigation; Sagar Samanta: Resources, Validation; Avik Bhanja: Writing- Original draft preparation, Formal analysis; Final manuscript preparation; Manas Das: Software, Validation; Pijush Payra: Conceptualization, Methodology

Acknowledgments: The authors express their sincere gratitude to the scientists of the Crustacea Division, Zoological Survey of India, Prani Vigyan Bhawan, M-Block, New Alipore, Kolkata, India, for their invaluable assistance in the identification and registration of this species under the Zoological Survey of India (ZSI).

Abstract: This study documents the occurrence of the leucosiid crab, Lyphira perplexa Galil, 2009, along the West Bengal coast of India. Specimens were collected from the Petuaghat seabeach and adjacent fishing harbor in Purba Medinipur District. The findings contribute to the limited understanding of the diversity and distribution of leucosiid crabs in Indian waters, specifically in the Bay of Bengal region. The observations include detailed morphological descriptions, habitat preferences, and geographic distribution. This contribution highlights the need for more extensive research on marine biodiversity along the Indian coast, emphasizing its ecological and conservation significance.

Keywords: Bay of Bengal, Crustacea, geographic distribution, Indian coast, marine biodiversity, morphological descriptions, pebble crab, Petuaghat seabeach, Purba Medinipur, taxonomy.

INTRODUCTION

Leucosiidae, commonly referred to as nut crabs or pebble crabs, is a distinctive family of small brachyuran crabs widely distributed on soft-bottom substrates and coral rubble habitats from the intertidal zone to continental slope depths (Alcock 1896). The family is particularly diverse in the Indo-West Pacific region (Tan 1995; Poore & Ahyong 2023), 765 leucosiid crabs (Brachyura: Leucosiidae) are considered one of the major brachyuran families worldwide (Ng et al. 2008; Beleem et al. 2017; Mohanty et al. 2019; WoRMS 2024). The crabs belong to leucosiid group are popularly known as nut and pebble crabs (Lee et al. 2009; Beleem et al. 2017). A checklist of marine brachyuran crabs from the Western Coast of India documented 84 species of the family Leucosiidae, out of which 22 species were reported from the western coast, whereas 52 species were recorded from the eastern coast of India (Dev-Roy 2013). Leucosiids are commonly associated with shallow seagrass meadows and, less frequently, rocky reef habitats. On tropical coral reefs, certain species possess highly eroded and flattened carapaces that closely resemble broken coral fragments or pieces of the calcareous alga Halimeda, providing effective camouflage within reef environments (Man 1888; Beleem et al. 2017). A higher diversity of the leucosiid group of the crabs is found along the Indian coast of the Bay of Bengal (Chopra 1933; Sarkar et al. 2024).

The genus Lyphira currently comprises 10 recognised species worldwide, including three species reported from Indian waters: L. georgei Trivedi et al., 2016; L. heterograna (Ortmann, 1892); and L. perplexa Galil, 2009. Members of the genus can be readily distinguished by a combination of morphological characters, including the ovate exopod of the third maxilliped, a transversely narrow first male pleonal somite, fused male pleonal somites 2–6 bearing a subterminal denticle, and the presence of a short apical process on the first male gonopod (Mohapatra et al. 2026).

This report represents the first documented occurrence of Lyphira perplexa along the West Bengal coast of India.

MATERIALS AND METHODS

Two male L. perplexa samples were collected from the Petuaghat seabeach area (21.7868° N, 87.8897° E) and near the Petuaghat fishing harbour (21.7947° N, 87.8833° E) in the Purba Medinipur District (Figure 1).

The specimens were measured with precision using Vernier calipers to the nearest 0.1 mm and a plastic ruler graduated to the nearest 0.1 cm. Specimens were identified, measured, and subsequently preserved in 10% formalin. Taxonomic identification was confirmed at the species level according to standard taxonomic keys (Galil 2009; Sudharma et al. 2014; Ebadi et al. 2018; Beleem et al. 2019; AL-Maliky 2020). Diagnostic assessments of the specimens were conducted in the Aquaculture Lab of the Department of Biological Sciences, Midnapore City College, Paschim Medinipur, West Bengal, India, and the Crustacea Division laboratory of the Zoological Survey of India, Prani Vigyan Bhawan, M-Block, New Alipore, Kolkata, India. One representative specimen was registered (Registration No. CR501) and deposited in the Crustacea Division of the Zoological Survey of India, Prani Vigyan Bhawan, M-Block, New Alipore, Kolkata, India for further reference and study.

RESULTS AND DISCUSSION

Systematic accounts

Class: Malacostraca Latreille, 1802

Order: Decapoda Latreille, 1802

Infraorder: Brachyura Latreille, 1802

Family: Leucosiidae Samouelle, 1819

Genus: Lyphira Galil, 2009

Lyphira perplexa Galil, 2009 (Image 1)

Materials examined: Two males, Petuaghat seabeach (Bay of Bengal), India, coll. Prabir Saho. 16.i.2024.

Description: Carapace is broadly oval and smooth. The posterior region of the carapace exhibits a prominent dome-shaped elevation, contributing to a trilobate appearance that is more pronounced compared to the anterior region. Lack of spines or sharp ridges, dorsal surface of the carapace exhibits a dense arrangement of closely spaced granules. Larger granules are prominently distributed in the hepatic, branchial, and intestinal regions. Along the posterior margin of the carapace, granules of varying sizes are organised in series, with finer granulation observed along the frontal margin and external maxillipeds. The pterygostomial region is distinctly adorned with prominent granules.

Anterior edge of the epistome displays a central indentation bordered by two acute inner angles located adjacent to the afferent branchial canals. The anterior margin of the abdominal sulcus is densely granulated, contributing to its distinct texture. Granulation on the cheliped’s merus is notably coarse on the anterior-posterior surface and the proximal region, gradually diminishing in size and prominence towards the distal region. The dorsal and ventral surfaces of the propodus, as well as the ventral inner surface, exhibit a pattern of conical granules (Image 2).

In the case of pereiopods, merus of the first pereiopod is characterized by a ventral row of spherical granules, whereas the meri of the second to fourth pereiopods possess elongated clusters of finer granules along their ventral margins. The thoracic sterna exhibit fine granulation, particularly in the anterior segments, with an absence of granules noted on the dorsal aspect of the apron. The gonopod is elongated, with its apical region covered in dense, hair-like structures. The tip of the gonopod is smooth and devoid of setae, culminating in a prominent, pointed aperture (Image 3).

Fresh Colouration: The carapace exhibits a rosy-brown hue. The merus of the anterior cheliped transitions from pinkish-brown at the proximal region to a lighter brown towards the propodus and dactylus. The distal portion of the chelae is whitish, with the tips of the fingers distinctly white. The carpus, thoracic sternum, and abdominal regions are uniformly creamy white, providing a distinct contrast to the darker appendages.

Habitat: Inhabits sandy or muddy seabed in shallow marine environments, such as intertidal zones, estuaries, and coastal areas.

Distribution: This species is primarily distributed across various regions in the Indo-West Pacific including the Gujarat coast, Kerala coast, Andaman Islands, Persian Gulf, Gulf of Oman, Kuwait, Iranian coasts, Arabian Gulf, and in the present study on the West Bengal coast of India (Galil 2009; Sudharma et al. 2014; Trivedi et al. 2016; AL-Maliky 2020).

Remarks: The species L. perplexa Galil, 2009 was first recorded from off the coast of Calicut, Kerala, by Sudharma et al. (2014) based on a male specimen, and they conducted the first DNA barcoding of the species in Indian waters. In 2013, Trivedi & Arya collected one male and one female specimen of L. perplexa from the Cochin Fishing Harbour, Kerala, India. Subsequently, they conducted a comparative analysis between L. perplexa and L. georgei to identify distinguishing morphological characteristics (Trivedi et al. 2016). The genus Lyphira differs from Philyra Leach, 1817 in several morphological features: it has an ovate exopod on the external maxilliped, a transversely narrow first abdominal segment in males, fused second to sixth abdominal segments, and lacks the subterminal denticle typically found on the fused male abdominal segments. L. perplexa can be distinguished from L. heterograna by the finer granule size on the surface and margins of the carapace (AL-Maliky 2020). While L. georgei is morphologically closest to L. perplexa, the proximal margin of L. georgei is gently concave, whereas in L. perplexa, it is deeply concave. Additionally, the male first left gonopod of L. georgei has a medial angular turn, whereas in L. perplexa, it is nearly straight (Trivedi et al. 2016).

CONCLUSION AND FUTURE DIRECTIONS

This study documents the first observation of the brachyuran crab L. perplexa Galil, 2009, from the West Bengal coast of India. Previously unreported along the eastern coast of India, this record extends the known distribution range of the species. Such findings enhance our understanding of regional biodiversity and contribute valuable data toward the effective management and conservation of marine ecosystems (Silambarasan et al. 2015). In order to improve these results, future studies should focus on molecular confirmation of the species’ identity to strengthen taxonomic accuracy, conduct population ecology studies to assess habitat preferences and conservation requirements, and map out comparative distributions in other coastal areas of India. Through these efforts, we will be able to better understand the ecological significance of L. perplexa and develop strategies for managing and protecting it in rapidly changing marine environments.

Table 1. Measurements of two Lyphira perplexa Galil, 2009 (male).

Parameters	Sample 1	Sample 2
Carapace
Carapace Width (CW)	18.90 mm	17.67 mm
Carapace Length (CL)	18.68 mm	17.42 mm
Carapace Depth (CD)	3.04 mm	2.67 mm
Abdomen
Abdomen Width (AW)	4.74 mm	4.50 mm
Total Abdomen Length (AL)	13.03 mm	12.3 mm
Telson Width (TW)	1.78 mm	1.45 mm
Penultimate Segment Length (PSL)	3.44 mm	3.22 mm
Penultimate Segment Width (PSW)	2.59 mm	2.38 mm
Abdomen Area (AA)	39.39 mm^2	37.02 mm^2
Appendage
Cheliped’s Dactylus Length (CDL)	8.83 mm	8.23 mm
Cheliped’s Propodus Length (CPL)	13.55 mm	12.59 mm
Cheliped’s Propodus Depth (CPD)	4.84 mm	4.51 mm
Cheliped’s Carpus length (CCL)	5.86 mm	5.47 mm
Cheliped’s Merus Length (CMEL)	13.02 mm	12.15 mm
Cheliped’s Merus Width (CMEW)	3.82 mm	3.47 mm
4^th Pereiopod Merus Length (4PML)	5.60 mm	5.18 mm
4^th Pereiopod Merus Width (4PMW)	1.25 mm	1.13 mm

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