Eumunida treguieri de Saint Laurent & Poupin 1996

Eumunida treguieri de Saint Laurent & Poupin, 1996

[New Japanese name: Shiro-yubi-tsuno-koshiori-ebi]

(Fig. 5B)

Eumunida (Eumunida) treguieri de Saint Laurent & Poupin, 1996: 352, figs 2a–h, 3j, 11c–d.

Eumunida treguieri.— Poupin 1996: 26, 27 fig. a.— Baba 2005: 211 (synonymies).— Puillandre et al. 2011: 331.

Material examined. JAMSTEC 106775, 1 juvenile (cl 5.5 mm; DNA voucher), R / V Kaimei, KM20-10 C, KM-ROV dive #132, Ritto Seamount, West Mariana Ridge, 21°48.72’N, 142°02.68’E, 666 m, 8 December 2020, associated with primnoid octocoral pick up by using manipulator.

Colouration in life. Carapace and anterior pleomeres whitish, with pinkish rostrum and supraocular spines; corneas darkly pigmented; antennae, chelipeds and pereopods 2–4 generally pinkish with distal parts of chela fingers and ambulatory dactyli whitish (Fig. 5B).

Distribution. Known with certainty only from French Polynesia and Indonesia at depths of 500–710 m (de Saint Laurent & Poupin 1996; Puillandre et al. 2011). The present specimen greatly extends the geographical range of the species to the northwestern Pacific.

Ecology. The present specimen was associated with a colony of an unidentified octocoral of Primnoidae collected by manipulator.

Remarks. Eumunida treguieri was originally described from French Polynesia by de Saint Laurent & Poupin, 1996.The authors questionably referred the record of E. picta from Hawaii by Titgen (1988) to E. treguieri. Puillandre et al. (2011) included specimens of the species from Indonesia in their molecular phylogenetic analyses.

The genetic analysis using the COI sequence shows that our specimen matches Eumunida treguieri (EU243562; genetic divergence 1.6%) (Puillandre et al. 2011). Eumunida treguieri is a large-sized species, attaining 44 mm in cl (de Saint Laurent & Poupin 1996). The present specimen is a juvenile (cl 5.5 mm), in which adult diagnostic characters remain not fully differentiated, and then identification based solely on morphology was difficult. Key characters of E. treguieri include: (1) carapace anterolateral margins (anterior to cervical groove) each with three spines; (2) carapace branchial surface evenly convex; (3) no epigastric spines on carapace; (4) posterior part of carapace with complete transverse striae; (5) thoracic sternite 4 with pair of well-developed spines on anterior margin; (6) posterior parts of pleomeres 2–4 tergite (posterior to second main transverse striae) with one secondary stria; (7) cheliped merus armed with three longitudinal rows of spines (ventral spines absent); (8) cheliped palm with setal pad on ventral surface (de Saint Laurent & Poupin 1996). In the present specimen, characters (1), (2), (3), (4), (5), and (7) are seen, whereas characters (6) and (8) are not exhibited, perhaps still not differentiated. Furthermore, the present specimen differs from the original description based on adult specimens in having the proportionally stronger branchial spines on the carapace, much slenderer chelipeds and the proportionally shorter dactyli of the pereopods 2–4. All these discrepancies are attributable to allometric variation.

The 16S rRNA gene sequence was also generated from the present specimen. Genetic divergence between E. treguieri represented by our specimen and other six species available for comparison (i.e., E. annulosa, E. funambrus, E. multispina, E. picta, E. smithii and E. sternomaculata) ranges from 1.8 to 5.7% (Table 3).

The species is recorded here for the first time from the northwestern Pacific. During the KM-ROV dives, we have encountered several large individuals of species of Eumunida, although not collected. We presume that at least some of them might represent E. treguieri.