Pseudanthessius imo, Uyeno, Daisuke, 2016

Uyeno, Daisuke, 2016, Copepods (Cyclopoida) associated with top shells (Vestigastropoda: Trochoidea: Tegulidae) from coastal waters in southern Japan, with descriptions of three new species, Zootaxa 4200 (1), pp. 109-130 : 124-128

Pseudanthessius imo n. sp.

( Figs 10–12 )

Type material. Holotype: adult female ( NSMT –Cr 24630), ex Tectus niloticus (Linnaeus, 1767) (Vestigastropoda: Trochoidea: Tegulidae ), off Saneku (28°12'N, 129°12'E), Kakeroma Island, Oshima Strait, 29 April, 2015, leg. D. Uyeno, S. Yokoyama . Allotype: adult male (NSMT–Cr 24631), collection data same as those of holotype. Paratypes: 2 adult females and 2 adult males (NSMT–Cr 24632), collection data same as those of holotype

Additional material. 1 adult female and 1 adult male ( NSMT –Cr 24633), ( NSMT –Cr 24633), ex T. niloticus , off Itchachi (26°20'N, 126°43'E), Kume Island, East China Sea, 3 March, 2012, leg. D. Uyeno, Y. Fujita, T. Naruse .

Description of holotype. Adult female. Body ( Fig. 10 A) cyclopiform, 2.94 long, depressed dorso-ventrally with greatest width at cephalosome; external segmentation distinct. Cephalosome distinctly articulated from first pedigerous somite, wider than long, 0.63 × 0.93. First to fourth pedigerous somites and urosomites free. Prosome 1.50 long. Genital double somite wider than long ( Fig. 10 A), 0.47 × 0.32. Abdomen progressively narrower posteriorly, composed of three free somites, 0.25 × 0.26, 0.18 × 0.21, and 0.19 × 0.20, respectively. Caudal ramus ( Fig. 10 A, D) 2.85 times longer than wide, 0.23 × 0.08, with six setae.

Rostrum ( Fig. 10 B) triangular, bearing distinct apex with round margin. Post-rostral process situated between bases of antennae ( Fig. 10 B). Antennule ( Fig. 10 E) 7-segmented; armature formula 4, 14, 6, 3, 4 + 1 aesthetasc, 2 + 1 aesthetasc, 7 + 1 aesthetasc; all setae naked. Antenna ( Fig. 10 F) 4-segmented, composed of coxobasis and 3- segmented endopod; coxobasis large, bearing single naked seta; first endopodal segment bearing simple seta on inner margin; second endopodal segment bearing three inner setae; third endopodal segment 1.44 times longer than wide, 61 × 43 µm, bearing four claws, one of them being elongate and three setae on distal part. Labrum ( Fig. 10 G) broad, bearing pair of posterior lobes. Mandible ( Fig. 10 H) bearing serrated blade with single hyaline tooth at base of convex margin of blade. Maxillule ( Fig. 11 A) represented by simple lobe armed with single inner and three distal setae. Maxilla ( Fig.11 B) 2-segmented; basal segment unarmed; terminal segment bearing serrated blade and three setae; inner seta large and spinulose. Maxilliped ( Fig. 11 C) 3-segmented, composed of unarmed syncoxa, basis bearing two simple setae, and conical endopodal segment with two simple elements.

Legs 1 to 4 ( Fig. 11 D–G) biramous, with 3-segmented rami. Leg 4 endopod unsegmented, almost as long as exopod, and with sinuous margins. Leg armature formula as follows:

Coxa Basis Exopod Endopod

Leg 1 0-1 1-0 I-0; I-1; III, I, 4 0-1; 0-1; I, 2, 3 Leg 2 0-1 1-0 I-0; I-1; III, I, 5 0-1; 0-2; II, I, 3 Leg 3 0-1 1-0 I-0; I-1; III, I, 5 0-1; 0-2; II, I, 2 Leg 4 0-1 1-0 I-0; I-1; III, I, 5 II

Intercoxal sclerites ( Fig. 11 D–G) of legs 1 to 4 unornamented. Leg 1 bearing basis with row of hair-like setules on inner margin. All spines spatulate with serrated margins and terminal flagellum. Both rami of legs 1 to 4 bearing rows of hair-like setules on outer and inner margins, except inner margin of basal segment of endopods on legs 1 to 3. Basal and middle endopodal segments of legs 1 to 3 each bearing row of fine spinules along distal margin and distal pointed projection on outer margin. Terminal endopodal segments of legs 1 and 2 each bearing single pointed projection on outer margin. Leg 5 ( Fig. 11 H) represented by simple spine and two naked setae. Leg 6 ( Fig. 10 C) represented by two small elements at genital opening.

Description of allotype. Adult male. Body ( Fig. 12 A) cyclopiform, 2.43 long, depressed dorso-ventrally with greatest width at cephalosome; external segmentations distinct. Cephalosome distinctly articulated from first pedigerous somite, wider than long, 0.55 × 0.80. First to fourth pedigerous somite and urosomites free. Prosome 1.14 long. Genital somite ( Fig. 12 A, B), 0.23 × 0.35. Abdomen progressively narrower posteriorly, composed of four free somites, 0.23 × 0.28, 0.20 × 0.24, 0.16 × 0.20, and 0.16 × 0.18, respectively. Caudal ramus ( Fig. 12 A) 3.77 times longer than wide, 0.22 × 0.06, with six setae.

Antennule, antenna, mandible, maxillule, and maxilla as in female. Antenna bearing third endopodal segment 1.48 times longer than wide, 57 × 38 µm. Maxilliped ( Fig. 12 D) 4-segmented; basal segment unarmed; second segment bearing two setae and row of fine spinules; third segment small without armature; terminal claw curved bearing two basal setae. Armature formula of legs 1 to 5 as in female. Leg 6 ( Fig. 12 B, C) represented by two simple setae on genital operculum.

Variability. Morphology of paratypes and other female specimens as in holotype. Measurements of the paratypes and other specimens (n = 3) as follows: body length 2.08–2.51 (2.31 ± 0.22); cephalosome length 0.58–0.65 (0.63 ± 0.04); cephalosome width 0.82–0.98 (0.90 ± 0.08); prosome length 1.05–1.33 (1.23 ± 0.15); genital double somite length 0.30–0.36 (0.33 ± 0.03); genital double somite width 0.29–0.37 (0.34 ± 0.04); first urosomite length 0.15–0.21 (0.19 ± 0.04); first urosomite width 0.27–0.30 (0.29 ± 0.02); second urosomite length 0.12–0.17 (0.14 ± 0.03); second urosomite width 0.22–0.28 (0.25 ± 0.03); anal somite length 0.17–0.19 (0.18 ± 0.01); anal somite width 0.20–0.23 (0.22 ± 0.01); caudal ramus length 0.21–0.26 (0.24 ± 0.02); caudal ramus width 0.07; length of third endopodal segment of antenna 57–74 (65 ± 8) µm; width of third endopodal segment of antenna 38–61 (46 ± 13) µm. Caudal ramus 3.00–3.56 (3.35 ± 0.31) times longer than wide. Third endopodal segment of antenna 1.21–1.65 (1.46 ± 0.23) times longer than wide.

Morphology of paratypes and other male specimens as in allotype. Measurements of male paratypes and additional specimens (n = 3) as follows: body length 2.08–2.30 (2.15 ± 0.13); cephalosome length 0.51–0.63 (0.58 ± 0.06); cephalosome width 0.68–0.85 (0.75 ± 0.09); prosome length 0.96–1.14 (1.03 ± 0.10); genital somite length 0.18–0.26 (0.22 ± 0.04); genital somite width 0.31–0.43 (0.37 ± 0.06); first urosomite length 0.17; first urosomite width 0.25–0.31 (0.28 ± 0.03); second urosomite length 0.18–0.20 (0.19 ± 0.01); second urosomite width 0.23–0.28 (0.25 ± 0.02); third urosomite length 0.13–0.16 (0.14 ± 0.02); third urosomite width 0.18–0.23 (0.20 ± 0.03); anal somite length 0.12–0.15 (0.14 ± 0.01); anal somite width 0.17–0.19 (0.18 ± 0.01); caudal ramus length 0.18–0.24 (0.21 ± 0.03); caudal ramus width 0.06–0.07 (0.07 ± 0.00); length of third endopodal segment of antenna 49–71 (61 ± 11) µm; width of third endopodal segment of antenna 36–42 (38 ± 3) µm. Caudal ramus 2.74–3.69 (3.24 ± 0.48) times longer than wide. Third endopodal segment of antenna 1.33–1.73 (1.59 ± 0.22) times longer than wide.

Remarks. Pseudanthessius imo n. sp. has four spines on the third exopodal segment of leg 4, a character shared with P. spinosus Shin & Kim, 2004 ( Shin & Kim, 2004) . The new species differs from P. spinosus by having the following characters: caudal ramus 2.5 to 4 times longer than wide (vs. less than 2 times); presence of postrostral process between bases of antenna (vs. process absent); third endopodal segment of antenna less than 2 times longer than wide, with four claws and three setae (vs. about 3 times longer than wide, bearing two claws, one clawlike seta, and three setae); bearing mandible with single hyaline tooth on convex margin (vs. with four small spinules); leg 4 bearing unsegmented endopod with sinuous both lateral margins (vs. with straight margins and two conical distal processes) (see Shin & Kim, 2004).

Attachment site. Mantle cavity.

Etymology. The specific name means “sweet potato” in Japanese. It alludes to shape of the irregularly constricted endopod of leg 4. The name is used as a noun in apposition.

Newly established Japanese name for species. Imo-ashi-kenmijinko.

Figures

FIGURE 10. Pseudanthessius imo n. sp., adult female, holotype NSMT – Cr 24630. A, habitus, dorsal; B, rostral area; C, genital aperture and leg 6, dorsal; D, left caudal ramus, dorsal; E, right antennule; F, right antenna, anterior; G, labrum, anterior; H, left mandible, anterior. Scale bars: A, 400 µm; B, 100 µm; C, D, F, G, 50 µm; E, 40 µm; H, 20 µm.

FIGURE 11. Pseudanthessius imo n. sp., adult female, holotype NSMT – Cr 24630. A, right maxillule, anterior; B, right maxilla, posterior; C, right maxilliped, posterior; D, left leg 1, anterior; E, left leg 2, anterior; F, left leg 3, anterior; G, left leg 4, anterior; H, right leg 5, dorsal. Scale bars: A, 20 µm; B, C, 40 µm; D – G, 100 µm; H, 50 µm.

FIGURE 12. Pseudanthessius imo n. sp., adult male, allotype NSMT – Cr 2463. A, habitus, dorsal; B, genital somite, ventral; C, right leg 6, ventral; D, left maxilliped, inner. Scale bars: A, 400 µm; B, 100 µm; C, 20 µm; D, 40 µm.