Panaietis flavellata sp. nov.

(Figs 4 –6)

urn:lsid:zoobank.org:act: 8C79DBCB-1B41-4BDA-8985-9B8DEDE1B5B3

Type material. Holotype: adult female (NSMT-Cr 26681), ex Angaria neglecta Poppe & Goto (Vetigastropoda: Trochida: Angariidae), Akamizu (31°15'N, 130°15'E), off Satsuma Peninsula, Kagoshima, the East China Sea, Japan, 4 May 2016, leg. D. Uyeno . Paratypes: 1 adult female (NSMT-Cr 26682), ex A. neglecta, Akamizu (31°15'N, 130°15'E), off Satsuma Peninsula, Kagoshima, the East China Sea, Japan, 3 August 2016, leg. D. Uyeno ; 1 adult female (NSMT-Cr 26683), ex A. neglecta, off Nomaike (31°25'N, 130°8'E), Satsuma Peninsula, Kagoshima, the East China Sea, Japan, 16 December 2018, leg. D. Uyeno ; adult female (NSMT-Cr 26684), ex A. neglecta, off Cape Bonomisaki (31°15'N, 130°13'E), Satsuma Peninsula, Kagoshima, the East China Sea, Japan, 2 January 2019, leg. D. Uyeno and H. Uyeno

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Holotype adult female. Body (Fig. 4A) cyclopiform, 3.01 long; external segmentation distinct. Cephalosome incompletely separated from first pediger, wider than long, 0.53 × 0.77. First to fourth pedigers and six urosomites free; third and fourth pedigers wider than cephalosome. Prosome 1.52 long. Genital somite bearing pair of lateral lobes (Fig. 4A, B), 0.26 × 1.01; paired genital openings situated on dorsal side. Abdomen composed of four free somites, 0.19 × 0.48, 0.18 × 0.46, 0.12 × 0.39, and 0.35 × 0.37, respectively. Caudal ramus (Fig. 4A, C) 2.40 times longer than wide, 0.43 × 0.18, with six minute setae.

Rostral area triangular without distinct apex. Antennule (Fig. 4D) 7-segmented; armature formula 6, 16, 4, 4, 4 + 1 aesthetasc, 2 + 1 aesthetasc, 7 + 1 aesthetasc; all setae simple. Antenna (Fig. 4E) 3-segmented, composed of coxobasis and 2-segmented endopod: coxobasis large, bearing simple distal seta; first endopodal segment bearing well developed conical protrusion with simple apical seta; second endopodal segment bearing four setae on inner margin and terminal claw, three claw-like spines, and three long distal setae on distal margin. Labrum (Fig. 4F) broad, bilobed. Mandible (Fig. 4G) bearing single lash-like seta with row of fine spinules on one of margin and apical serrated lash with two basal hyaline teeth. Maxillule (Fig. 4H) represented by unsegmented lobe bearing inner elongate protrusion tipped with minute element, outer basal seta, and three short distal elements. Maxilla (Fig. 4I) 2-segmented; proximal segment rod-like, unarmed; distal segment bearing five sharp teeth and two basal setae. Maxilliped (Fig. 4J) 2-segmented, composed of unarmed stout proximal portion and distal portion.

Legs 1 to 4 (Fig. 5 A–D) biramous, bearing 3-segmented rami. Leg armature formula as follows:

Intercoxal sclerites (Fig. 5 A–D) of legs 1 to 4 unarmed. All spines spatulate. Proximal and middle endopodal segments of legs 1 to 4 bearing pointed protrusions on outer margin. Leg 5 (Fig. 5E) 2-segmented, situated on posteroventral surface of pediger (Fig. 4A); proximal segment incompletely fused to fifth pediger with small simple seta on outer margin; distal segment elongate bearing three spatulate spines and single seta. Leg 6 represented by simple seta at genital opening.

Male. Unknown.

Variability. The morphology of the female paratypes as in holotype. The measurements of the body parts of paratypes (n = 3) are as follows: body length 2.57–3.17 (2.83 ± 0.37); cephalosome length 0.48–0.55 (0.51 ± 0.05); cephalosome width 0.64–0.79 (0.72 ± 0.11); prosome length 1.37–1.65 (1.51 ± 0.20); genital somite length 0.21–0.26 (0.24 ± 0.04); genital somite width 0.56–0.64 (0.60 ± 0.06); first urosomite length 0.13–0.21 (0.17 ± 0.06); first urosomite width 0.41–0.46 (0.43 ± 0.05); second urosomite length 0.13–0.25 (0.19 ± 0.08); second urosomite width 0.40–0.44 (0.42 ± 0.03); third urosomite length 0.14–0.20 (0.17 ± 0.05); third urosomite width 0.36–0.36 (0.36 ± 0.00); anal somite length 0.27–0.30 (0.28 ± 0.02); anal somite width 0.34–0.37 (0.35 ± 0.02); caudal ramus length 0.43–0.45 (0.44 ± 0.01); caudal ramus width 0.14–0.16 (0.15 ± 0.01). Caudal ramus 2.65–3.13 (2.89 ± 0.34) times longer than wide.

Remarks. Of all its congeners, Panaietis flavellata sp. nov. shares leg 5 situated on the posteroventral side of the fifth pediger only with P. yamagutii (Yamaguti 1936; Izawa 1976; Ho 1981; Kim 1998). The new species clearly differs from P. yamagutii by following characters: inner margin of second segment of antenna greatly protruded at base of small seta (vs. not protruded); leg 3 endopod bearing single seta on third endopodal segment (vs. two setae) (Yamaguti 1936; Izawa 1976).

Attachment site. Mouth cavity to esophagus.

Etymology. The specific name of the new species, flavellata, refers to the spatulate and fan shaped spines on legs.

Newly established Japanese name for species. Katabegai-no-haramushi.