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.
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
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