Hexapleomera urashima Tanabe et al., 2017

Tanabe, Yuki & Kakui, Keiichi, 2019, Two Hexapleomera species from Japan, with a new species description and discussion of phylogenetic relationships within Hexapleomera (Crustacea: Tanaidacea), Zootaxa 4648 (2), pp. 318-336 : 321-322

Hexapleomera urashima Tanabe et al., 2017

[Japanese name: Urashima-tanaisu]

Figure 1A

Hexapleomera urashima Tanabe et al., 2017 , 146–160, figs 2–6; Kakui & Tanabe 2018, 6, fig. 2.

Material examined. Type material: Holotype (female, ICHUM-5381), allotype (male, ICHUM-5382), and five female and five male paratypes (ICHUM-5383–5387, 5389–5393); for detailed information on these specimens, see Tanabe et al. (2017). Other material: one female (ICHUM-5848; BL 2.54 mm, CW 0.58 mm), seven slides and one vial, INSD accession number LC474839 , collected from epiphytic algae on a loggerhead sea turtle bycaught in a set-net (left tag no. 13445; SCL 59.5 cm, sex indeterminate), Funakoshi Bay, Iwate Prefecture (39°24'48"N 142°01'23"E), 2.viii.2017, by C. Kinoshita and T. Fukuoka; one female (ICHUM-5950; BL 3.50 mm, CW 0.83 mm), one vial, INSD accession number LC485015 , collected from epiphytic algae on a nesting loggerhead sea turtle (left tag no. Y7115; SCL 85.3 cm, female) on Nagata-hama, Yakushima Island, southern Japan (30°24.933'N, 130°26.352'E), 30.vi.2016, by Y. Tanabe.

Amended diagnostic characteristics. Labium with palp fused to outer lobe. Maxilliped with coxa bearing two setae; endite with two tiny dorso-subdistal and two distal spiniform setae. Cheliped with 5–7 dorsodistal simple setae on carpus; region between bases of dactylus and fixed finger with five or six simple setae. Propodus of pereopod 1 with inner subdistal plumose seta. Pleopodal rami with slight pigmentation (retained in ethanol). Basal article of pleopod 3 with two outer setae. Uropod with four articles, including basal article.

Supplemental information on female and male morphology. Pleopodal rami with slight pigmentation (retained in ethanol; Fig. 1A ).

Variation and stability. We reexamined the holotype, allotype, and five female and five male paratypes, and observed one additional specimen of H. urashima . Table 3 lists the states for eight characters listed in Tanabe et al. (2017) and three characters we added. We did not check following four characters, which showed variation among specimens in Tanabe et al. (2017): the numbers of setae i) on the maxillipedal basis; ii) in the region posterior to eye; iii) in the inner region of the endopod of pleopods 1, 2, and 3; and iv) on the maxillular palp.

In addition to the four stable characters presented in Tanabe et al. (2017), our observation of the type specimens and one additional specimen (seven females and six males in total) revealed: i) a single inner subdistal plumose seta on the pereopod-1 propodus; ii) 5–6 setae in the region between the bases of the chelipedal dactylus and fixed finger; iii) 5–7 setae in the dorsodistal region of the chelipedal carpus; iv) five spiniform setae on the carpus of pereopods 4–6; and v) slight pigmentation on the pleopodal rami ( Fig. 1A ).

Genetic information. A partial COI sequence (655 nt, translating to 218 amino acids) for one H. urashima specimen collected off the eastern coast of Iwate Prefecture (ICHUM-5848; INSD accession number LC474839 ) is identical to one of two haplotype sequences reported for the species by Tanabe et al. (2017) ( INSD accession number LC322243 ). A partial 18S sequence (1942 nt) was determined in one specimen collected from Yakushima Island (ICHUM-5950; INSD accession number LC485015 ).

Distribution. This species is known from the surface of carapaces of loggerhead sea turtles ( Caretta caretta ) collected at Yakushima Island ( Tanabe et al. 2017) and off the eastern coast of Iwate Prefecture (this study), and from among the fouling community on a tether line on Yakushima Island ( Kakui & Tanabe 2018).

Remarks. Tanabe et al. (2017) did not report which specimen was used for illustrations of the cheliped (fig. 3M, M1); we confirmed that these were based on the holotype female.

After a detailed reexamination of this species, we amend the setal position name for setae on the propodal palm. The five setae in the region between the bases of the dactylus and fixed finger of the cheliped in the holotype correspond to i) four outer simple setae at the insertion of the dactylus, and ii) one dorsoproximal simple seta on the cutting surface ( Tanabe et al. 2017: p. 150). The six setae in the same region of the allotype correspond to i) five outer simple setae at the insertion of the dactylus, and ii) one dorsoproximal (sic; actually subdistal) simple seta on the propodal palm ( Tanabe et al. 2017: p. 156).

Figures

FIGURE 1. The condition of pigmentation on the pleopodal rami in H. urashima (A, ICHUM-5389) and H. sasuke sp. nov. (B, ICHUM-5850), ventral views, fixed specimens.Arrows indicate the endopod of left pleopod 1. Scale bars: 0.1 mm.