Actumnus ngankeeae sp. nov. and Pilumnus swajayai Ng & Rahayu, 2021, pilumnid crabs from Japan (Crustacea: Decapoda: Brachyura)

Masatsune Takeda ¹, Hironori Komatsu ²

⁰Department of Zoology; National Museum of Nature and Science; Tokyo; 4-1-1 Amakubo; Tsukuba; Ibaraki 305-0005; Japan. takeda@kahaku.go.jp.

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December 8, 2024

View abstract on PubMed

Summary

Two new rare crab species, Actumnus ngankeeae and Pilumnus swajayai, were discovered in Japan. This finding expands the known diversity of the Pilumnidae family in the region.

Area Of Science

Marine Biology
Crustacean Taxonomy
Zoology

Background

The family Pilumnidae comprises numerous crab species, with ongoing discoveries contributing to our understanding of marine biodiversity.
Accurate identification and description of new species are crucial for ecological and evolutionary studies.

Purpose Of The Study

To describe two new and rare crab species belonging to the family Pilumnidae, Actumnus ngankeeae sp. nov. and Pilumnus swajayai.
To document the occurrence of these species in Japanese waters, specifically the Ogasawara (Bonin) Islands and Ryukyu Islands.

Main Methods

Morphological examination of crab specimens, focusing on carapace shape, granulation, setation, and limb armature.
Comparative analysis with related species and genera to confirm taxonomic placement.
Geographical distribution recording.

Main Results

Actumnus ngankeeae sp. nov. is described from the Ogasawara Islands, characterized by a convex, granulate carapace and stout chelipeds.
Pilumnus swajayai is reported from the Ryukyu Islands, distinguished by its tomentose covering, specific carapace armature, and spinulated ambulatory legs.
The record of Pilumnus swajayai in Japan represents its second known occurrence globally.

Conclusions

The discovery and description of Actumnus ngankeeae and Pilumnus swajayai enhance the known crab diversity in Japan.
These findings contribute to the taxonomic and biogeographic understanding of the Pilumnidae family in the Indo-Pacific region.