Journal of Threatened Taxa | www.threatenedtaxa.org | 26 January 2017 | 9(1): 9771–9773
Muntasir Akash 1 & Mostafa A.R. Hossain 2
1 House 37, Road 1, Block A, Bonosree, Dhaka 1219, Bangladesh
2 Department of Fish. Biology & Genetics, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
1 email@example.com (corresponding author), 2 firstname.lastname@example.org
Editor: Biju Kumar, University of Kerala, Thiruvananthapuram, India. Date of publication: 26 January 2017 (online & print)
Manuscript details: Ms # 2943 | Received 29 July 2016 | Final received 17 November 2016 | Finally accepted 10 January 2017
Citation: Akash, M. & M.A.R. Hossain (2017). First record of the Two-striped Box Crab Calappa bilineata Ng, Lai & Aungtonya, 2002 (Brachyura: Calappidae) from St. Martin’s Island, Bangladesh. Journal of Threatened Taxa 9(1): 9771–9773; 9771-9773
Copyright: © Akash & Hossain 2017. Creative Commons Attribution 4.0 International License. JoTT allows unrestricted use of this article in any medium, reproduction and distribution by providing adequate credit to the authors and the source of publication.
Funding: Department of Zoology, University of Dhaka (funding the survey); World Bank and Forest Department, Ministry of Environment and Forest, Government of the People’s Republic of Bangladesh (funding IUCN Updating Red List Bangladesh Project).
Competing interests: The authors declare no competing interests.
Acknowledgements: We owe our gratitude to the ‘IUCN Updating Red List Bangladesh Project’ (funded by World Bank and led by the Forest Department, MoEF, GoB) to create the sphere of this discovery.
Crabs in the family Calappidae are heterotrematan, eubrachyuran species distinguished by their normal ambulatory dactyli, triangular merus of third maxillipeds, buccal cavern without canal and not paddle-like, the right and always larger chela armed with a pair of special cutting teeth designed for ‘cutting’ open gastropods (Ng & Tan 1984). Rounded, dome-shaped, ovate to transversely ovate carapace being usually broader than long with wing-like side extensions that conceal the four pairs of walking legs; the broad, flat claws are held like shields, protecting the crab’s front surface and completing the box-like appearance, hence, imply their common name Box Crab (Ng 1998; Ahmed & Hossain 2008).
Annotated checklists of bachyuran crabs published by Ng et al. (2008) and of decapod crustaceans published by Grave et al. (2009) list nine extant genera, with the genus Calappa holding the largest diversity, represented by 43 species.
Calappid crabs have a wide distribution, whereas, the genus Calappa is concentrated mostly along the Western Pacific, Indian Ocean and in the Eastern Mediterranean (Sakai 1976; Dai & Yang 1991; Chen & Xu 1991; Chen 1993; Galil 1997; Holthuis 2001; Ng et al. 2002). The Indian Subcontinent has been hitherto represented by eight Calappa species which are C. capellonis (Laurie, 1906), C. bilineata Ng, Lai & Aungtonya, 2002, C. exanthematosa Alcock & Anderson, 1894, C. gallus (Herbst, 1803), C. guerini Brito-Capello, 1871, C. hepatica (Linnaeus, 1758), C. lophos (Herbst, 1782) and by C. pustulosa Alcock, 1896 (Galil 1997; Deb 1999; Lai et al. 2006; Ahmed & Hossain 2008; Kumar et al. 2007, 2013; Galil & Ng 2010; Ng et al. 2011). As information on crustacean diversity from this region is still limited, available reports of Two-striped Box Crab C. bilineata are only from Sri Lanka, Andaman Sea, Red Sea and from the western coast of India (Ng et al. 2002; Kumar et al. 2013). This present study records C. bilineata for the first time from Bangladesh as well as from the northern part of the Bay of Bengal.
Saint Martin’s Island forms the southernmost part of Bangladesh lying in the northeastern part of the Bay of Bengal, about 9km off from the southern tip of Cox’s Bazar-Teknaf peninsula (Fig. 1). This small island (8km2) is the only coral island of the country, an ecologically critical area (ECA) and rich in marine biodiversity.
As part of a survey of a BS (honours) study tour conducted by the Department of Zoology, University of Dhaka, two specimens of box crabs were caught with a beach seine net from the northern beach in front of the Hotel Prince Heaven. Those box crabs were collected live and then photographed, as part of the project entitled “Updating Species Red List of Bangladesh” led by IUCN Bangladesh, the first ever attempt considering the crustacean fauna of Bangladesh was made (IUCN Bangladesh 2015). The goal was to evaluate and determine the biodiversity status, national abundance, habitat condition of native crustaceans and depict their threats, to advance related conservation initiatives. The project, in the process, sought after evidence of new records, rediscoveries and quality photographs.
These crab photographs were then submitted to IUCN Bangladesh Team and later were identified as Calappa bilineata, turning out to be a new record of box crab species within the geographical area of Bangladesh.
Class: Malacostraca Latreille, 1802
Order: Decapoda Latreille, 1802
Infraorder: Brachyura Linnaeus, 1758
Family: Calappidae Milne-Edwards, 1837
Genus Calappa Weber, 1795
Calappa bilineata Ng, Lai & Aungtonya, 2002 (Image 1)
Common name: Two-striped Box Crab
Material examined: 07.xii.2012, two individuals (male), Saint Martin’s Island, Bangladesh, 20038′07.50”N & 92019′34.68″E, coll. M. Akash.
Diagnosis: Two-striped Box Crabs as carapace with two bold longitudinal stripes locating on median carapace, in addition, the purplish to maroon longitudinally convex dorsal surface, laterally flattened chelae with multidentate dorsal margin. Legs were devoid of any pattern or texture; outer surface of chelae were evenly colored.
Description: Carapace is smooth and arched dorsally aided with small, flat tubercles on the front. Clypeiform structure highly prominent, edges frilled with setae. From the structure, four teeth are projected laterally from posterior margin. As of Ng et al. (2002), anterolateral margin is crested and beaded. Posterior carapace margin with seven well developed granulated, pale yellowish teeth, median tooth sub-equal to adjacent teeth with distinct concavity. Lateral margin of second abdominal segment angular.
Habit and Habitat: During extraction from the seines, specimen showed noticeable aggression relative to the other species, might be a reflection of the species’ highly carnivorous, predatory nature. The beach from which specimens were collected represents sandy flats at low tide, devoid of limestone rock compared to the other parts of the island. The adjoining shallow sea-shelf, however, has submerged coral associations and dead coral colonies (Tomascik 1997). Formation of such sandy inter-tidal layers supports an efficient burrowing habitat for callappid crabs.
Remarks: This new record of a benthic crab from the northern Bay of Bengal indicates the potential of the ecologically critical St. Martin’s island ecosystem as well as the largest bay of the world itself. It is believed that in-depth expeditions within the vast marine boundary of Bangladesh will bring out more unique and bewildering species accounts.
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