Research Article |
Corresponding author: Chien-Hui Yang ( chyang@ntou.edu.tw ) Academic editor: Sameer Pati
© 2024 Mani Prema, Chien-Hui Yang, Samuthirapandian Ravichandran, Peter K. L. Ng.
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:
Prema M, Yang C-H, Ravichandran S, Ng PKL (2024) Carcinoplax mistio Ng & Mitra, 2019 (Crustacea, Decapoda, Goneplacidae): additional records and genetic differentiation of allied taxa. ZooKeys 1214: 91-103. https://doi.org/10.3897/zookeys.1214.131500
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The goneplacid crab, Carcinoplax mistio Ng & Mitra, 2019, was originally described from West Bengal, India, in the northern Indian Ocean. Additional material of C. mistio from off Tamil Nadu in the southeast of India revealed a high degree of size-associated variation in the structures of the anterolateral tooth of the carapace, chelipeds, and male and female pleons. In addition to an in-depth morphological examination of C. mistio, this study also records the natural coloration of the species and conducts a genetic comparison (with mitochondrial COI and 16S rRNA genes) with its close relatives, C. haswelli (Miers, 1884) and C. purpurea Rathbun, 1914. Molecular comparison of C. mistio with its morphologically closest congener, C. haswelli from northern Australia and the western Pacific, corroborates their status as separate species. The genetic sequence of C. mistio, however, is similar to that of C. purpurea from the West Pacific, although these two species can easily be distinguished by distinct carapace and ambulatory leg characters. The present study provides some possible explanations for the genetic and morphological incongruence observed between C. mistio and C. purpurea and highlights the need for a detailed molecular study for Carcinoplax H. Milne Edwards, 1852, to appreciate the evolution of various morphological characters in the genus.
Brachyura, COI, genetic and morphological incongruence, goneplacid crab, Goneplacoidea, India, systematics, 16S rRNA
The goneplacid crab genus, Carcinoplax H. Milne Edwards, 1852, comprises 26 species from the Indo-West Pacific (
While describing C. mistio from West Bengal, India,
The material used for morphological examination is deposited in the Zoological Survey of India, Kolkata (
In addition to C. mistio, C. haswelli and C. purpurea, four other species of Carcinoplax [C. ischurodous (Stebbing, 1923), C. longimanus, C. nana Guinot, 1989 and C. tomentosa Sakai, 1969], are also included for the molecular analysis. Goneplax rhomboides (Linnaeus, 1758) was selected as the outgroup. The samples for molecular analyses were from the Zoological Reference Collection of the Lee Kong Chian Natural History Museum, National University of Singapore (
Material, sampling localities and GenBank accession numbers of Carcinoplax and outgroup used in this study. “#” sequences downloaded from GenBank. N.C. - no sequence available.
Species | Locality | Voucher Nos. | GenBank Accession Nos. | |
---|---|---|---|---|
(code) | COI | 16S rDNA | ||
C. haswelli (1) | Gulf of Tonkin |
|
OP163291 | PQ163823 |
C. haswelli (2) | Off Singapore |
|
OP163292 | N.C. |
C. ischurodous | MZ434779 # | MZ424933 # | ||
C. longimanus (1) | Taiwan |
|
OP163293 | PQ163824 |
C. longimanus (2) | MZ434781 # | MZ424935 # | ||
C. longimanus (3) | MZ434783 # | MZ424936 # | ||
C. mistio (1) | India |
|
OP163294 | PQ163825 |
C. mistio (2) | India |
|
OP163295 | PQ163826 |
C. nana | Philippines |
|
OP163296 | PQ163827 |
C. purpurea (1) | Taiwan |
|
OP163297 | PQ163828 |
C. purpurea (2) | Taiwan |
|
OP163298 | PQ163829 |
C. purpurea (3) | Philippines |
|
OP163299 | PQ163830 |
C. tomentosa | Taiwan |
|
OP163300 | PQ163831 |
Goneplax rhomboides | MG935224 # | JN591672 # |
Crude genomic DNA was extracted from the muscles of the pleon using a DNeasy® Blood and Tissue Kit (Qiagen, Hilden, Germany) following the protocol of the manufacturer. Molecular markers were selected as the mitochondrial COI and 16S rRNA genes, while the sequences amplification using LCO1490/HCO2198 (~657 bp,
Superfamily Goneplacoidea MacLeay, 1838
Family Goneplacidae MacLeay, 1838
Genus Carcinoplax H. Milne Edwards, 1852
Carcinoplax (purpurea)
? –
Carcinoplax purpurea
–
Carcinoplax sinica
–
Carcinoplax mistio Ng & Mitra, 2019: e2019004, figs 1, 2, 6A, 7A, G, H, 8A–G, 9A, B.
Carcinoplax haswelli
–
Holotype. India • ♂ (29.2 × 19.0 mm); northern Bay of Bengal, Fresargunj Fishing Harbour; 24 Feb. 2017; coll. local fishermen by trawl;
India • 4 ♂♂ (35.1 × 30.0 mm, 29.2 × 22.3 mm, 25.1 × 18.2 mm, 23.2 × 29.2 mm), 5 ♀♀ (37.1 × 31.0 mm, 36.2 × 30.1 mm, 32.1 × 25.2 mm, 31.0 × 25.2 mm, 26.1 × 24.0 mm); southern Bay of Bengal, eastern Tamil Nadu, Pazhayar Fishing Port; 11°21'N, 79°50'E; depth 50–100 m; 2016–2020; coll. M. Prema & S. Ravichandran; CASAU CR-1031 • 1 ♂ (29.7 × 19.6 mm), 1 ♀ (43.2 × 29.2 mm); same collection data as for preceding; 2016–2020; CASAU CR-1032 • 2 ♂♂ (37.6 × 25.8 mm, 32.0 × 21.3 mm), 7 ♀♀ (37.9 × 24.5 mm, 37.0 × 25.1 mm, 34.0 × 22.9 mm, 32.3 × 21.6 mm, 31.2 × 21.1 mm, 29.5 × 19.6 mm, 27.6 × 25.6 mm,); same collection data as for preceding; 18 Mar. 2018; CASAU CR-1033 • 1 ♂ (26.4 × 18.0 mm), 1 juv. ♀ (19.7 × 13.4 mm); same collection data as for preceding; Mar. 2018; CASAU CR-1034 • 4 ♂♂ (36.0 × 23.8 mm, 33.0 × 22.7 mm, 32.5 × 22.2 mm, 31.5 × 21.4 mm), 1 ovig. ♀ (39.0 × 26.6 mm), 1 ♀ (36.1 × 23.4 mm); same collection data as for preceding; 2020–2021; CASAU CR-1035 • 3 ♂♂ (29.2 × 20.8 mm, 29.2 × 20.5 mm, 27.6 × 19.4 mm); same collection data as for preceding; 12 Jan. 2022; CASAU CR-1036 • 1 ♂ (33.× 23.4 mm); same collection data as for preceding; CASAU CR-1037 • 2 ♀♀ (37.3 × 24.6 mm, 35.9 × 23.7 mm); same collection data as for preceding; 26 Mar. 2023; CASAU CR-1038 • 2 ♂♂ (26.2 × 18.1 mm, 24.8 × 16.4 mm), 2 ♀♀ (32.2 × 22.0 mm, 29.5 × 19.4 mm); same collection data as for preceding; 11 Feb. 2024; CASAU CR-1039 • 7 ♀♀ (37.9 × 26.0 mm, 36.2 × 24.3 mm, 34.7 × 22.5 mm, 33.5 × 24.0 mm, 30.5 × 20.5 mm, 29.2 × 20.1 mm, 25.1 × 17.1 mm); same collection data as for preceding; 11 Feb. 2024; CASAU CR-1040.
Modified from
Carcinoplax mistio Ng & Mitra, 2019 A, C, D, E–I male (33.3 × 23.4 mm) (CASAU CR-1037) B, J–L male (24.8 × 16.4 mm) (CASAU CR-1039) A, B dorsal view of carapace C frontal view of cephalothorax D third maxillipeds E thoracic sternites 3–6, pleonal somites and telson E pleonal somites and telson G–L dorsal and outer views of chelae. Scale bars: 5.0 mm (A–L).
Carcinoplax mistio Ng & Mitra, 2019 A–F female (33.5 × 24.0 mm) (CASAU CR-1040); G– J male (33.3 × 23.4 mm) (CASAU CR-1037) K male (25.1 × 18.2 mm); A dorsal view of carapace B–D dorsal and outer views of chelae E pleon and telson F thoracic sternites with position of vulvae G dorsal view of left G1 H dorso-lateral view of left G1 I ventral view of left G1 J ventro-lateral view of left G1 K lateral view of left G1. Scale bars: 5.0 mm (A–F); 1.0 mm (G–K).
The present specimens of C. mistio were collected from 50–100 m depth, off the coastal waters of Tamil Nadu state, Bay of Bengal, India. The three type specimens were obtained from West Bengal, also from a fishing port but without depth data (
Carapace orange, cheliped fingers and upper surface of ambulatory legs white (Fig.
Northern Indian Ocean: Bay of Bengal (West Bengal and off Tamil Nadu coast, India;
The present specimens of C. mistio agree well with the type account (
In the types as well as in the smaller males (e.g., 26.4 × 18.0 mm, CASAU CR-1034; 24.8 × 16.4 mm, CASAU CR-1039) and most of the larger specimens of the present collection, the second anterolateral tooth of the carapace is prominent, being sharp and curved (Figs
The cheliped carpal spine of male C. mistio specimens examined, including the holotype male, is relatively more rounded and relatively shorter (Figs
The lateral margins of pleonal somite 6 of large males is gently convex, gradually converging towards the telson, which is similar to that of the holotype of C. mistio (Fig.
The proportions of the male telson vary regardless of size with the width-to-length ratios of three males (33.3 × 23.4 mm, CASAU CR-1037; 26.2 × 18.1 mm, 24.8 × 16.4 mm, CASAU CR-1040) are 0.76, 0.88 and 0.67, respectively. Overall, the male telson is slightly broader with the lateral margins being more concave (Fig.
The mesial margin of the distal two-thirds of the G1 is gently concave in large specimens of C. mistio (Fig.
The genetic comparisons for seven species of Carcinoplax, including C. mistio, are interesting (Fig.
Pairwise distance based on Kimura-2-parameter (K2P) model of partial mitochondrial COI (within and under the diagonal) and 16S rDNA (value in the brackets and above the diagonal) sequences among Carcinoplax species. Goneplax rhomboides (Linnaeus, 1758) was treated as an outgroup.
Carcinoplax haswelli | C. ischurodous | C. longimanus | C. mistio | C. nana | C. purpurea | C. tomentosa | Goneplax rhomboides | |
---|---|---|---|---|---|---|---|---|
Carcinoplax haswelli | 0.002 | 0.102 | 0.098–0.101 | 0.035–0.037 | 0.105 | 0.035 | 0.134 | 0.128 |
C. ischurodous | 0.199–0.202 | 0.078–0.083 | 0.095–0.097 | 0.080 | 0.095 | 0.093 | 0.071 | |
C. longimanus | 0.172–0.178 | 0.176–0.178 | 0.002–0.008 [0.0–0.004] | 0.082–0.088 | 0.078–0.084 | 0.082–0.086 | 0.084–0.087 | 0.113 |
C. mistio | 0.103–0.105 | 0.190 | 0.159–0.164 | 0.0 [0.002] | 0.093–0.095 | 0.0–0.002 | 0.118–0.121 | 0.113–0.116 |
C. nana | 0.165–0.167 | 0.154 | 0.124–0.127 | 0.179 | 0.093 | 0.065 | 0.105 | |
C. purpurea | 0.099–0.105 | 0.192–0.195 | 0.159–0.169 | 0.003–0.008 | 0.181–0.184 | 0.005–0.011 [0.0] | 0.118 | 0.113 |
C. tomentosa | 0.173–0.175 | 0.209 | 0.203–0.211 | 0.203 | 0.160 | 0.200–0.203 | 0.105 | |
Goneplax rhomboides | 0.187–0.189 | 0.122 | 0.204–0.205 | 0.198 | 0.172 | 0.195–0.203 | 0.219 |
A detailed molecular study of Carcinoplax will be necessary to appreciate the evolution of the various morphological characters in the genus as currently defined (sensu
We sincerely appreciate Dr Paul F. Clark (Department of Life Science, The Natural History Museum, London, England) and Dr Shane T. Ahyong (Australian Museum, Sydney, Australia) for many constructive comments in reviewing the manuscript. Prof. Tin-Yam Chan kindly provided specimens from the National Taiwan Ocean University.
The authors have declared that no competing interests exist.
No ethical statement was reported.
The Earth Watch Institute of India, New Delhi, Citizen Science Fellowship (PR/01/2022-2023) is acknowledged for facilitating funding for the fieldwork along the coast of Tamil Nadu, Bay of Bengal.
MP and SR collected the samples. MP prepared the photographs. CHY conducted the molecular works and prepared Fig.
Mani Prema https://orcid.org/0000-0003-2694-3034
Chien-Hui Yang https://orcid.org/0000-0002-4594-3622
Samuthirapandian Ravichandran https://orcid.org/0000-0002-8632-5062
Peter K. L. Ng https://orcid.org/0000-0001-5946-0608
All of the data that support the findings of this study are available in the main text.