[Crustacea • 2025] Metaplax pristis • A New Species of the Genus Metaplax H. Milne Edwards, 1852 (Decapoda: Brachyura: Varunidae) from Vietnam

 

Metaplax pristis

Hsu, Shih & Ngo, 2025 

 

DOI: doi.org/10.11646/zootaxa.5693.4.2

Abstract

Metaplax H. Milne Edwards, 1852, is a genus in the family Varunidae H. Milne Edwards, 1853, distributed across the Indo-West Pacific, with 10 described species. Among them, Metaplax crenulata (Gerstaecker, 1856) was previously thought to be present in both the Indian Ocean and the western Pacific (Vietnam). However, our study, based on morphological and molecular evidence, indicates that specimens from the Indian Ocean and Vietnam represent distinct species. Since the type locality of M. crenulata is unknown, we conducted comparative analyses of the syntypes alongside specimens from the Indian Ocean and Vietnam. Morphological examinations revealed that the syntypes closely resemble the Indian Ocean specimens, whereas the Vietnamese specimens exhibit clear morphological differences, particularly in the male suborbital cristae and the proportions of the ambulatory legs. Furthermore, cytochrome c oxidase subunit I (COI) sequence analysis showed a 5.8% genetic divergence between the two groups, further confirming that they represent separate species. Based on these findings, we describe the species from Vietnam as new.

Crustacea, new species, Metaplax crenulata, Metaplax pristis, morphology, cytochrome c oxidase subunit I (CoI)

Color in life and habitat of Metaplax pristis sp. nov.
A–C, E, F, male, holotype (44.1 × 33.1 mm) (NChuZooL 17352);
D, female, paratype (43.6 × 32.5 mm) (NChuZooL 17353);
G, juvenile (specimen not examined); H, habitat in T. T. Can Thanh, Can Gio, Ho Chi Minh City, Vietnam (arrowed).

Metaplax pristis sp. nov.

Etymology. The species is named after Pristis, which is the genus of sawfish. This new species name is derived from the distinctive meri of its ambulatory legs, which have numerous curved spines along the meri margins, resembling the snout of a sawfish.

Jhih-Wei HSU, Hsi-Te SHIH and Xuan Quang NGO. 2025. Description of A New Species of the Genus Metaplax H. Milne Edwards, 1852 (Decapoda: Brachyura: Varunidae) from Vietnam. Zootaxa. 5693(4); 482-500. DOI: doi.org/10.11646/zootaxa.5693.4.2 [2025-09-19]

[Crustacea • 2024] Parapyxidognathus tshiansue & P. ongia • A Review of the varunid crab Genus Parapyxidognathus Ward, 1941 (Decapoda: Brachyura: Varunidae), with Descriptions of Two New Species

  

Parapyxidognathus tshiansue

 Hsu & Shih, 2024

DOI: 10.1093/jcbiol/ruae039 

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Abstract

Species of Parapyxidognathus Ward, 1941 are distributed across tropical Indo-West Pacific to temperate downstream rivers and in estuaries. The genus previously included only one species, Parapyxidognathus deianira (De Man, 1888). We examined specimens from Parapyxidognathus and its closely related genus, Pyxidognathus A. Milne-Edwards, 1879 from the eastern Indian Ocean and western Pacific, focusing on their morphological characters. The results also support the reclassification of Pyxidognathus fluviatilis Alcock, 1900 into Parapyxidognathus, as well as the establishment of two new species from the western Pacific, Pa. tshiansue sp. nov. and Pa. ongia sp. nov. The identity of the species is supported by evidence from mitochondrial 16S rDNA and cytochrome oxidase subunit 1 (COI) genes. There are now four species in Parapyxidognathus distinguishable by the characters of the anterolateral teeth of the carapace, the pleon, and the first gonopods of the male, and the female vulvae.

  

Parapyxidognathus tshiansue sp. nov. 

Parapyxidognathus ongia sp. nov. 

Jhih-Wei Hsu and Hsi-Te Shih. 2024. A Review of the varunid crab Genus Parapyxidognathus Ward, 1941 (Decapoda: Brachyura: Varunidae), with Descriptions of Two New Species. Journal of Crustacean Biology., 44(2); ruae039. DOI: doi.org/10.1093/jcbiol/ruae039

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