Journal of Threatened Taxa | www.threatenedtaxa.org | 26 November 2021 | 13(13): 20084–20089

 

ISSN 0974-7907 (Online) | ISSN 0974-7465 (Print) 

https://doi.org/10.11609/jott.7465.13.13.20084-20089

#7465 | Received 24 May 2021 | Final received 12 September 2021 | Finally accepted 11 November 2021

 

 

First record of a freshwater crab, Maydelliathelphusa masoniana (Henderson, 1893) (Decapoda: Brachyura: Gecarcinucidae) from West Bengal, India

 

Ram Krishna Das

 

Department of Industrial Fish & Fisheries, Asutosh College, 92, S.P. Mukherjee Road, Kolkata, West Bengal 700026, India.

ramkrishnazoology@gmail.com

 

 

 

Editor: A. Biju Kumar, University of Kerala, Thiruvananthapuram, India. Date of publication: 26 November 2021 (online & print)

 

Citation: Das, R.K. (2021). First record of a freshwater crab, Maydelliathelphusa masoniana (Henderson, 1893) (Decapoda: Brachyura: Gecarcinucidae) from West Bengal, India. Journal of Threatened Taxa 13(13): 20084–20089. https://doi.org/10.11609/jott.7465.13.13.20084-20089

 

Copyright: © Das 2021. 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: West Bengal Biodiversity Board; Memo No. 1221/3K (Bio)-5/2019.

 

Competing interests: The author declares no competing interests.

 

Acknowledgements:  The author is grateful to Shri Bishu Tirkey, a resident of Cooch Behar district for his support in the field. Author thanks vice principal, Asutosh College for research facilities. The author is also grateful to West Bengal Biodiversity Board for financial support. The author gratefully acknowledges three anonymous reviewers and subject editor for their constructive comments and valuable suggestions.

 

 

 

Abstract: The genus Maydelliathelphusa Bott, 1969 includes five species, M. masoniana (Henderson, 1893), M. edentula (Alcock, 1909), M. falcidigitis (Alcock, 1910), M. harpax (Alcock, 1909), and M. lugubris (Wood-Mason, 1871), and is endemic to India. Out of the five species, only Maydelliathelphusa lugubris (Wood-Mason, 1871) was reported from West Bengal previously. Present study reports the second species, M. masoniana (Henderson, 1893), from West Bengal, India for the first time.

 

Keywords: Crustacea, Decapoda, description, diagnosis, endemic, freshwater crabs, Gecarcinucidae, taxonomy.

 

 

 

Freshwater crabs belonging to infraorder Brachyura of order Decapoda are important in terms of nutrient cycles, bio-indicators of environments, disease transmission and small scale fisheries (Cumberlidge et al. 2009; Valarmathi 2017; Harhoglu et al. 2018; Kotwal & Sharma 2020). They are characterized by a broad carapace-covered cephalothorax having five pairs of thoracic legs or pereiopods (one pair of chelipeds, four pairs of walking legs) and a reduced abdomen (Deb 1999; Yeo et al. 2008). These crabs complete their entire life cycle in freshwater environments without moving to saltwater (Yeo et al. 2008).

The freshwater crab diversity of India comprises a total of 127 species divided into two families: Potamidae Ortmann, 1896 and Gecarcinucidae Rathbun, 1904 (Pati 2021).  The genus Maydelliathelphusa Bott, 1969 belongs to the Gecarcinucidae and is represented by five species: M. masoniana (Henderson, 1893), M. edentula (Alcock, 1909), M. falcidigitis (Alcock, 1910), M. harpax (Alcock, 1909), and M. lugubris (Wood-Mason, 1871) (Ng et al. 2008). All of these are found in India (Valarmathi 2017), but only M. lugubris is reported from West Bengal (Deb 1999). The present study records M. masoniana for the first time from West Bengal.

 

Materials & Methods

During an ichthyological survey, two specimens of M. masoniana were collected from a small stream (26.2290N, 89.2550E, elevation 32m) of the Brahmaputra River system in Cooch Behar district, West Bengal, India (Image 1). The collected specimens were immediately photographed; morphometric measurements were taken and preserved in 70% alcohol after anaesthetized. The specimens were identified as per the standard identification keys of Henderson (1893), Alcock (1910a,b), and Ng et al. (2008). The specimens were deposited in the Aquatic Animal Biodiversity Museum of the Department of Industrial Fish & Fisheries, Asutosh College, Kolkata (Reg. No. AABM/IFF/AC/CRUSTACEA/CRAB-1 to 2).

 

Taxonomy

Class Malacostraca Latreille, 1802

Order Decapoda Latreille, 1802

Infraorder Brachyura Linnaeus, 1758

Section Eubrachyura Saint Laurent, 1980

Superfamily Gecarcinucoidea Rathbun, 1904

Family Gecarcinucidae, Rathbun, 1904

Genus Maydelliathelphusa Bott, 1969

 

Maydelliathelphusa masoniana (Henderson 1893) (Image 2A & 3A)

Holotype:  Telphusa masoniana Henderson, 1893 (pl. XXXVII. fig. 1–4)

Type locality: River Jumna, a series; North-West Provinces, four males (Day); “India” two dried specimens (Brit. Mus.)

Material examined: Reg. No. AABM/IFF/AC/CRUSTACEA/CRAB/1 to 2, Date 16.v.2021, two individual (01 male and 01 female), small stream (26.2290N, 89.2550E) of the Brahmaputra River system in Cooch Behar district, West Bengal, India, collected by R.K. Das.

Measurement: Carapace length 55–60 mm, carapace width 75–82 mm, weight 180–190 g) (Details are presented in Table 1).

Diagnosis: The carapace is broader than long, slightly depressed; epigastric cristae distinct, rugose, located somewhat anterior to postorbital cristae without merging with the latter (Image 2A, 3A); postorbital cristae well defined towards the sides; a wide gap between frontal margin and postorbital cristae; external orbital tooth prominent; anterolateral margin with prominent epibranchial tooth; wide frontal margin, frontal median triangle incomplete (Image 2B & 3B); cervical groove well developed; mesogastric furrow deep, slightly bifurcated posteriorly; chelipeds asymmetric and massive (Image 2 E), carpus with a strong spine, propodus and dactylus with strong teeth which can meet only at the tips creating a wide gap between them (Image 2E); 6th pleonal somite of adult male slightly longer than breadth with concave lateral margin (Image 2F).

Description: The morphometric measurements of the identified species are presented in Table 1. The carapace enlarged, broader than length (cw/cl= 1.36), slightly depressed, dorsal surface smooth; epigastric cristae distinct, rugose, located anterior to postorbital cristae without merging with the latter; postorbital cristae well defined towards the sides, a wide gap between frontal margin and postorbital cristae (Image 2A, 3A); orbits large, external orbital tooth prominent; wide frontal margin (fw/cw= 0.18); anterolateral margin with prominent epibranchial tooth; cervical groove well defined; mesogastric furrow deep, slightly bifurcated posteriorly; eyes smaller than orbital space, eyestalk short, narrow (Image 2B, 3B ); mandibular palp three-segmented; 1st, 2nd maxilliped with long flagellum on exopods; 3rd maxilliped almost cover buccal cavity when closed (Image 2B, 3B); ischium subrectangular, longer than broad, with a narrow medial groove; merus nearly pentagonal, broader than long; exopod slender, longer than ischium, reaching the base of merus, with a long flagellum (Image 2D ).

Chelipeds smooth, asymmetrical and massive, right cheliped larger than the left (Table 2, 3) carpus, with strong spine, propodus and dactylus with 12 to 13 strong teeth which can meet only at the tips creating a wide gap between them (Image 2E); ambulatory legs (P2–P5) stout, shorter than chelipeds; P3 longest and P5 shortest,  dactylus longer than propodus with four rows of spines on the margins.

Pleon of the male smooth, glabrous, conical; pleonal somites 1, 2 almost rectangular, narrower than somite 3; pleonal somites 3–5 trapezoidal; 6th pleonal somite slightly longer than breadth with concave lateral margin; telson conical with equal length and breadth (Image 2C, 2 F); thoracic sternites smooth, glabrous; suture S4/S5, S5/S6, S7/S8 discernible; sternopleonal cavity deep, long, reaching to imaginary line joining cheliped coxae; G1 stout, distal portion tapering gradually, slightly turned outward; G2 elongated; G1 longer than G2, approximately 1.7 times the length of G2 (Image 2G).

In the female, pleonal somite 1 is the shortest; pleonal somites 2–5 are progressively longer; 6th pleonal somite is longest (Image 3C, 3D); telson triangular; vulvae on S6 (VD/SW= approximately 0.38), large, deep, touching the suture S5/S6 (Image 3 E).

Colour: Dark brown in fresh condition.

Habit & Habitat: M. masoniana creates small burrows at the adjoining areas of soil and water of the stream for living and breeding purpose (Image 4A–C). Their preferred habitat is the small or narrow canals or streams with slow-moving water. They are nocturnal in habit.

Distribution: India: Uttar Pradesh (Krishnamurthy 1995), Assam, Meghalaya, Jammu & Kashmir (Kotwal & Sharma 2020), West Bengal (present study).

Conservation status: As per the IUCN Red List of threatened species, the species belongs to the Least Concern (LC) category (Cumberlidge 2008).

                                                                                                                                                                                                         Discussions

The freshwater crab, M. masonia was originally described as Telphusa masonina in the year 1893 by Henderson using type locality of river Jumna, North-West Provinces, India. Alcock (1910) transferred the species to the sub-genus Barythelphusa Alcock, 1909 of the Genus Parathelphusa Edwards, 1853 using a specimen from northern to central India. Bott (1970) created the subgenus Maydelliathelphusa and placed the species in that subgenus in a revisionary work. Specimen collected in the present study is in agreement with the original description of M. masoniana. In an earlier study, Krishnamurthy (1995), reported the species from Uttar Pradesh, India. Recently, the species has been reported from Jammu & Kashmir (Kotwal & Sharma 2020).

 

Conclusion

The present study extends the distribution of M. masoniana to West Bengal. As all the five species of the genus Maydelliathelphusa are similar morphologically, molecular taxonomy to confirm the morphological taxonomy of the species is warranted. Further studies are needed to investigate the biology, threat and conservation of this species, and to evaluate the potentiality of the species for commercial fisheries in that region.

 

Table 1. Morphometric measurement of carapace and right cheliped of the identified crab (mm).

Characters

M. masoniana (n= 1) (Male)

M. masoniana (n= 1) (Female)

Carapace length

60

55

Carapace width

82

75

Distance between epibranchial tooth

62

60

Frontal width

15

14

Posterior width of the carapace

28

26

Merus length

38

32

Merus width

25

20

Carpus length

30

25

Carpus width

27

20

Propodus length

80

57

Propodus width

36

27

Dactylus length

55

42

 

Table 2. Morphometric measurement of chelipeds (right and left) of M. masoniana (Male) in mm.

Podomeres

Right cheliped

Left cheliped

Merus length

38

37

Merus width

25

21

Carpus length

30

27

Carpus width

27

23

Propodus length

80

62

Propodus width

36

27

Dactylus length

55

42

 

Table 3. Morphometric measurement of chelipeds (right and left) of M. masoniana (Female) in mm.

Podomeres

Right cheliped

Left cheliped

Merus length

32

30

Merus width

20

18

Carpus length

25

23

Carpus width

20

18

Propodus length

57

52

Propodus width

27

22

Dactylus length

42

33

 

 

Keys to the species of Maydelliathelphusa

 

1 (a) Epigastric and postorbital crests on either side united …………………………………... ...………..  M. edentula               

1 (b) Epigastric and postorbital crests are incompletely or indistinctly separated from one another ...... ……………....  2

 

2 (a) External orbital tooth broad and blunt; lateral epibranchial tooth small and blunt, or obsolescent; carapace flattish ……………………………………….......…………………………....…. 3

2 (b) External orbital tooth and lateral epibranchial tooth prominent; carapace convex/ tumid …………...………...………… 4                                                         

 

3 (a) 6th abdominal segment of male squarish with lateral side slightly concave  ……………………………………. M. lugubris

3 (b) 6th abdominal segment of male is longer than distal breadth ………………...………………… ……. M. falcidigitis

 

4 (a) Carapace less convex;  chelipeds are symmetric ........... ......………… ………………………………………… M. harpax

4 (b) Carapace greatly convex; chelipeds are asymmetric ……………………………….………… ……………...... M. masoniana

 

 

For images - - click here

 

 

References

 

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Alcock, A. (1910b). Brachyura I, Fasc. II. The Indian fresh water crabs-Potamonidae. Catalogue of the Indian Decapod Crustacea in the collection of the Indian Museum. Calcutta, 135 pp, pls. 1–14.

Bott, R. (1970). Die Süßwasserkrabben von Europa, Asien, Australien und ihre Stammesgeschichte. Eine Revision der Potamoidea und Parathelphusoidea (Crustacea, Decapoda). Abhandlungen der Senckenbergischen aturforschenden Gesellschaft  526: 1–338.

Cumberlidge, N. (2008). Maydelliathelphusa masoniana. The IUCN Red List of Threatened Species. e. T134371A3946162. Downloaded on 23 May 2021. https://doi.org/10.2305/IUCN.UK.2008.RLTS.T134371A3946162.en

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