Research Article |
Corresponding author: Peter K.L. Ng ( peterng@nus.edu.sg ) Academic editor: Sammy De Grave
© 2019 Peter K.L. Ng, P. Priyaja, A. Biju Kumar, S. Suvarna Devi.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Ng PKL, Priyaja P, Kumar AB, Devi SS (2019) A collection of crabs (Crustacea, Brachyura) from the southwestern coast of India, with a discussion of the systematic position of Nectopanope Wood-Mason in Wood-Mason & Alcock, 1891 (Euryplacidae). ZooKeys 818: 1-24. https://doi.org/10.3897/zookeys.818.32108
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A report on the brachyuran crabs collected from the southwestern coast of India by the Indian research vessel FORV Sagar Sampada is presented. The material consists of 13 species from three genera and five families, of which four are new records for India: Heteroplax maldivensis (Rathbun, 1902) (Euryplacidae), Cryptopodia collifer Flipse, 1930 (Parthenopidae), Thalamita macrodonta Borradaile, 1903 (Portunidae), and Paraxanthodes cumatodes (MacGilchrist, 1905) (Xanthidae). The cruise also obtained the first known male of Nectopanope rhodobaphes Wood-Mason in Wood-Mason & Alcock, 1891 (type species of Nectopanope Wood-Mason in Wood-Mason & Alcock, 1891), and its characters show that it is in fact a member of the Euryplacidae Stimpson, 1871. The genus had previously been incorrectly classified in the Xanthidae MacLeay, 1838.
Brachyura , Euryplacidae , Indian Ocean, new records, rare species, revised taxonomy, systematics
We here report on a small but noteworthy collection of brachyuran crabs obtained by a fishery research vessel off the southwestern coast of India in 2017. While consisting of only 13 species from three genera and five families, the material obtained includes several rare species, including one which has not been seen since 1891.
The discovery of a male of Nectopanope rhodobaphes Wood-Mason in Wood-Mason & Alcock, 1891, is significant as the family position of the genus Nectopanope Wood-Mason in Wood-Mason & Alcock, 1891, has been uncertain, because it was previously known only from the type female. The male characters show that Nectopanope is a member of Euryplacidae Stimpson, 1871, and close to Psopheticoides Sakai, 1969, from the western Pacific. Nectopanope is rediagnosed, while Nectopanope rhodobaphes is redescribed and figured. A male of the rarely reported parthenopid Cryptopodia collifer Flipse, 1930, not previously known from India, is figured. The euryplacid Heteroplax maldivensis (Rathbun, 1902), the rarely reported portunid Thalamita macrodonta Borradaile, 1903, and the xanthid Paraxanthodes cumatodes (MacGilchrist, 1905), are also recorded from India for the first time.
All specimens were collected during an exploratory survey (cruise 360) of FORV Sagar Sampada belonging to the Center for Marine Living Resources & Ecology (CMLRE) under the Ministry of Earth Sciences, India, in May 2017, conducted along the southwestern coast of India. Specimens were collected using grabs and dredged from depths ranging from 50–200 m. The material studied is in the museum collections of the Department of Aquatic Biology and Fisheries, University of Kerala (DABFUK).
Measurements provided are of the maximum carapace width and length, respectively. The classification and terminology used follows
2 males (9.1 × 17.6 mm, 9.0 × 17.5 mm), 8°19.972'N, 76°35.897'E, 100 m.
Overall dorsal habitus. A Notosceles serratifrons (Henderson, 1893), male (9.1 × 17.6 mm) B Nursilia tonsor Alcock, 1896, female (6.0 × 5.3 mm) C Arcania gracilis Henderson, 1893, male (7.7 × 5.5 mm) D Coleusia urania (Herbst, 1801), female (10.1 × 12.0 mm) E Xiphonectes tuberculosus (A. Milne-Edwards, 1861), male (21.1 × 12.4 mm) F Thalamita macrodonta Borradaile, 1902, female (8.4 × 5.8 mm).
1 young female (6.0 × 5.3 mm), 8°22.727'N, 76°43.545'E, 50 m.
The species was first described from the Andaman Sea (
1 juvenile male (7.7 × 5.5 mm), 7°16.713'N, 77°37.582'E, 200 m.
The genus was revised by
1 juvenile female (10.1 × 12.0 mm), 7°27.978'N, 77°32.297'E, 100 m.
The identity of this species and the confused status of the types were resolved by
1 male (21.1 × 12.4 mm), 1 female (18.6 × 10.1 mm), 7°27.978'N, 77°32.297'E, 200 m.
This species was described from Hawaii but has since been reported from all across the Indo-West Pacific to Madagascar (A.
1 young male (18.2 × 10.2 mm), 8°58.270'N, 76°17.365'E, 50 m.
This is a well-known and widely distributed species in the Indo-West Pacific (
1 young female (8.4 × 5.8 mm), 8°22.727'N, 76°43.545'E, 50 m.
The present specimen from India is incomplete and not in good condition, but agrees with the description and figures of T. macrodonta by
Nectopanope Anonymous, 1891: 56 (nomen nudum).
Nectopanope Wood-Mason in Wood in Wood-Mason & Alcock, 1891: 261.
Carapace (Fig.
The type species of Nectopanope has been somewhat confused. Only one species, Nectopanope longipes, was recognised in
Nectopanope Wood-Mason in Wood-Mason & Alcock, 1891, was originally placed in Cancridae Latreille, 1802, by Wood-Mason (in
The family position of Nectopanope is difficult because its only species, N. rhodobaphes, has previously only been known from one female specimen. Wood-Mason (in
The study of the present male specimen resolves the systematic position of Nectopanope. The structures of the male pleon and gonopods leave no doubt that Nectopanope is in fact a member of Euryplacidae Stimpson, 1871. Nectopanope is only superficially resembles Eurycarcinus (and the Pilumnidae) due to similar carapace features. Their male pleons and gonopods, however, are completely different (cf.
In Euryplacidae, the general shape and structure of the carapace as well as smoothness of the surfaces of Nectopanope most closely resembles Psopheticoides Sakai, 1969 (with only one species, P. sanguineus Sakai, 1969), from the western Pacific. They also share a similar eye morphology. The eye of Psopheticoides is large and is distinctly flattened dorsoventrally, with the structure appearing reniform (
The carapace anterolateral margin of Nectopanope has three distinct teeth (Figs 2, 3A, C) (with only two teeth in Psopheticoides, with the external orbital tooth very broad;
Nectopanope
rhodobaphes
Wood-Mason in Wood-Mason & Alcock, 1891: 261;
1 male (18.4 × 14.7 mm), 7°27.978'N, 77°32.297'E, 200 m.
As for genus.
Carapace (Figs
Third maxillipeds (Fig.
Chelipeds (P1) (Figs
Nectopanope rhodobaphes Wood-Mason in Wood-Mason & Alcock, 1891, male (18.4 × 14.7 mm), India. A anterior thoracic sternum, pleon, buccal cavity and third maxillipeds B thoracic sternum and pleon C posterior thoracic sternum and pleon D anterior thoracic sternum and sternopleonal cavity E subdorsal view of right cheliped F inner view of right cheliped G–J second to fourth ambulatory legs, respectively (all to same scale).
Ambulatory legs (P2–P5) (Figs
Thoracic sternum (Figs
Pleon (Fig.
G1 (Fig.
The colour of the fresh type specimen was described as “a beautiful deep-sea pink, with a dotted, V-shaped, white mark between the gastric and branchial regions.” (Wood-Mason in
The type female (Fig.
Goneplax
maldivensis
Rathbun, 1902: 124, figs 3–5;
“?[Goneplax] maldivensis”:
Otmaroplax maldivensis : Števčić 2005: 134 [genus name nomen nudum]
“Heteroplax” maldivensis:
Henicoplax
maldivensis
:
1 male (9.9 × 6.3 mm), 7°27.978'N, 77°32.297'E, 100 m.
Henicoplax Castro & Ng, 2010, was established for Indo-West Pacific species that had been previously classified in Goneplax Leach, 1814, or HeteroplaxStimpson, 1858. Five species are currently recognised: H. eriochir Castro & Ng, 2010, H. maldivensis (Rathbun, 1902) [type species], H. nitida (Miers, 1879a), H. pilimeles Castro & Ng, 2010, and H. trachydactylus Castro & Ng, 2010.
The present specimen is clearly H. maldivensis as redescribed and figured at length by
Henicoplax maldivensis (Rathbun, 1902), male (9.9 × 6.3 mm), India. A overall dorsal habitus B dorsal view of carapace C frontal view of cephalothorax D left third maxilliped E anterior thoracic sternum and pleon F thoracic sternum and pleon G posterior thoracic sternum and pleon H outer view of chelae.
Heteroplax maldivensis is thus far known for certain only from the Maldives (
1 female (9.4 × 8.8 mm), 7°48.004'N, 77°27.754'E, 50 m.
This species was described from off Sri Lanka and Andamans by
A Pseudolambrus beaumonti (Alcock, 1895), female (9.4 × 8.8 mm) B Rhinolambrus contrarius (Herbst, 1804), female (10.5 × 10.0 mm) C–F Cryptopodia collifer Flipse, 1930, male (17.5 × 10.6 mm) G, H Paraxanthodes cumatodes (MacGilchrist, 1905), male (8.3 × 5.5 mm). A, B, C, G, H overall dorsal habitus D ventral view of cephalothorax E, F outer view of chelae.
1 young female (10.5 × 10.0 mm), 3 juveniles (largest 6.8 × 6.8 mm), 7°48.004'N, 77°27.754'E, 50 m.
The present materials are all juveniles, with none of the gonopod structures of the males developed even though the chelipeds are elongated. The pronounced “neck-like” constriction in adults of this species has still not developed (Fig.
Cryptopodia
collifer
Flipse, 1930: 66, fig. 41;
1 male (17.5 × 10.6 mm), 7°27.978'N, 77°32.297'E, 100 m.
Five species of Cryptopodia H. Milne Edwards, 1834, are known from India (
The lateral margins of the rostrum are straight in the holotype of C. collifer (cf.
Xanthodes
cumatodes
MacGilchrist, 1905: 205;
Xanthias
cumatodes
:
Paraxanthodes
cumatodes
:
1 male (8.3 × 5.5 mm), 8°58.270'N, 76°17.365'E, 50 m.
The taxonomic problems associated with Paraxanthodes Guinot, 1968, and the allied genera Monodaeus Guinot, 1967, and Medaeops Guinot, 1967, and Takedax Mendoza & Ng, 2012, as well the generic affinities of species previously classified in these taxa have been discussed at length by
We refer the present specimen to P. cumatodes, described from the western Indian Ocean by
Gonopods. A–E Nectopanope rhodobaphes Wood-Mason in Wood-Mason & Alcock, 1891, male (18.4 × 14.7 mm) F–H Henicoplax maldivensis (Rathbun, 1902), male (9.9 × 6.3 mm) I–M Cryptopodia collifer Flipse, 1930, male (17.5 × 10.6 mm) N–P Paraxanthodes cumatodes (MacGilchrist, 1905), male (8.3 × 5.5 mm). A, F left G1 (ventral view) B, G left G1 (dorsal view) C distal part of left G1 (ventral view) D distal part of left G1 (dorsal view); left G2. Scales bars: 0.5 mm (A, B, E–H–P); 0.25 mm (C, D).
The authors wish to thank the Director of CMLRE, Kochi, India, for providing the cruise facilities on board surveys on FORV Sagar Sampada during which the samples were collected. We are grateful to Santanu Mitra of the Zoological Survey of India (Kolkata) for his help in searching for some of Alcock’s specimens; and to JC Mendoza for discussions on the taxonomy of Paraxanthodes. The many helpful comments on the manuscript by Peter Castro and JC Mendoza are much appreciated. The first author thanks the University of Kerala for inviting him to conduct a crustacean taxonomy workshop there which began the study of this interesting collection of Indian material.