Anthessius isamusi, Uyeno, Daisuke & Nagasawa, Kazuya, 2012

Uyeno, Daisuke & Nagasawa, Kazuya, 2012, New species of the copepod genus Anthessius Della Valle, 1880 (Poecilostomatoida: Anthessiidae) from Turbo marmoratus Linnaeus (Gastropoda: Turbinidae) collected during the KUMEJIMA 2009 Expedition *, Zootaxa 3367, pp. 60-68 : 61-66

publication ID	https://doi.org/ 10.5281/zenodo.281669
DOI	https://doi.org/10.5281/zenodo.6172885
persistent identifier	https://treatment.plazi.org/id/03ED87B3-FFA4-FFDB-FF2E-FD58FC25F8AE
treatment provided by	Plazi
scientific name	Anthessius isamusi
status	sp. nov.

Treatment

Anthessius isamusi n. sp.

(Figs. 1–3)

Material examined. Holotype, female ( NSMT –Cr 21665), ex Turbo marmoratus Linnaeus (Gastropoda: Turbinidae ), off Ebi-ana (26°17ʹN, 126°47ʹE), Kumejima Island, the Ryukyu Islands, East China Sea, Japan, 13 November 2009. Allotype: a male ( NSMT –Cr 21666) and Paratypes: 4 females and 1 male ( NSMT –Cr 21667); 2 female and 1 male ( RUMF –ZC–1503), Collection data of allotype and paratypes same as that of holotype.

Description of female holotype. Body (Fig. 1A) 2240 long, excluding caudal rami (n = 7). Cephalothorax ovoid, shorter than wide 969 × 1202, widest at posterior 3/4. Three free thoracic somites in prosome distinctly separated and narrowing posteriorly. Urosome 5-segmented, 768 long. Genital complex barrel-shaped, shorter than wide 227 × 292. Anal somite (Fig. 1C) shorter than wide 124 × 152, unarmed. Caudal ramus (Fig. 1C) longer than wide 140 × 67, length/width ratio 2.08, slightly longer than anal somite, with 6 setae; outer lateral seta naked and located on subterminal, most outer and inner seta plumose, 2 middle setae with small spinules on margin.

Rostrum (Fig. 1B) broad. Antennule (Fig. 1D) 7-segmented, with armature formula 4, 17, 4, 3, 4 + 1 aesthetasc, 2 + 1 aesthetasc, 7 + 1 aesthetasc; all setae naked. Antenna (Fig. 1E) 3-segmented; proximal segment with 1 distal seta on anterior surface; middle segment with 1 subterminal seta on anterior surface; terminal segment bearing 1 short and 3 long setae proximally, 1 subterminal seta, and distal tip carrying 1seta and 2 strong hook-like claws, one of them slender and long, and the other small.

Labrum (Fig. 1F) bilobed bearing median incision. Mandible ( Fig. 2 View FIGURE 2 A) bearing 1 lash-like serrated inner seta and apical serrated lash with 2 proximally, bifurcated teeth at outer lash basis. Maxillule ( Fig. 2 View FIGURE 2 B) bearing 2 long and 2 small setae, 3 blunt and 1 comb-like processes. Maxilla ( Fig. 2 View FIGURE 2 C) 2-segmented; proximal segment rod-like, unarmed; distal segment tapering into pointed process, with 2 large and 1 small teeth on convex side and 2 spines near basis. Maxilliped ( Fig. 2 View FIGURE 2 D) digitiform, with obscure suture line and distally tapering process with 1 setule.

Legs 1 to 4 ( Fig. 2 View FIGURE 2 E–H) with coxa, basis, and 3-segmented rami; leg armature formula as follows:

Coxa of legs 1 to 4 with single row of small denticles on distal tip. Basis of legs 1 to 4 with single row of hairs along inner margin. Legs 1 to 3 bearing single row of fine spinules on margin of basis between endopod attachment area and outer protrusion. Proximal segment of exopod of legs 1 to 4 bearing single row of denticles along outer margin and rows of setules along inner margin; spines foliaceous, serrated along both lateral sides, excluding distal plumose spines along inner margin; terminal segment serrated along outer margin. Endopods of legs 1 to 4 fringed Anthessius isamusi , female, holotype NSMT–Cr 21665: A, habitus dorsal; B, rostrum area, ventral; C, anal somite and caudal rami, ventral; D, left antennule, posterior; E, left antenna, anterior; G, labrum. Scales: A = 500 μm; B = 200 μm; C, D, E = 100 μm; F = 50 μm.

with setules along outer margin; proximal and middle segment bearing pointed process on distal tip and single row of spinules along distal margin; spines foliaceous with serrated margin, except for leg 1, legs 3 and 4 ornamented with single row of setules along inner margin. Leg 5 ( Fig. 3 View FIGURE 3 A) 2-segmented; proximal segment incompletely fused to 5th pedigerous somite with 1 naked seta on dorsal surface; terminal segment longer than wide 144 × 55, with length/width ratio of 2.60, bearing 3 blunt spines and 1 naked seta, spinules along posterior quarter of inner margin and near base of each outer 3 elements. Leg 6 ( Fig. 3 View FIGURE 3 A) rod-like with 2 elements.

Variability of measurement. Paratype females share all important morphological characters with the holotype. Measurement range of their body parts and appendages of female type series (n = 7) was as follows: body (excluding caudal rami) length 2063–2240 (2150 ± 65), cephalothorax length 857–989 (928 ± 46), cephalothorax width 1040–1202 (1095 ± 58), urosome length 714–865 (791 ± 53), genital complex length 206–254 (225 ± 18), genital complex width 270–297 (286 ± 10), anal somite length119–126 (124 ± 2), anal somite width 142–162 (152 ± 7), caudal ramus length 133–145 (140 ± 4), caudal ramus width 63–70 (66 ± 2), caudal ramus length/width ratio 1.99–2.28 (2.16 ± 0.08), terminal segment length of leg 5 124–144 (134 ± 8), terminal segment width of leg 5 38–55 (44 ± 6), length/width ratio of terminal segment of leg 5 2.60–3.42 (3.09 ± 0.39).

Description of male allotype. Body ( Fig. 3 View FIGURE 3 B) as in female, 1735 long, excluding caudal rami. Cephalothorax ovoid, shorter than wide 766 × 792, widest at posterior 3/4. Urosome ( Fig. 3 View FIGURE 3 B) 6-segmented, 629 long. Genital somite ( Fig. 3 View FIGURE 3 C) shorter than wide 203 × 221. Anal somite shorter than wide 75 × 122. Caudal ramus longer than wide 93 ± 55, with length/width ratio of 1.69. Sexual dimorphism distinctly present in antennule ( Fig. 3 View FIGURE 3 D), antenna ( Fig. 3 View FIGURE 3 E), and maxilliped ( Fig. 3 View FIGURE 3 F). Antennule 7-segmented bearing 4 additional aesthetascs ( Fig. 3 View FIGURE 3 D), with armature formula 4, 17+ 3 aesthetasc, 4, 3+ 1 aesthetasc, 4 + 1 aesthetasc, 2 + 1 aesthetasc, 7 + 1 aesthetasc; all setae naked. Antenna ( Fig. 3 View FIGURE 3 E) as in female except proximal segment with long comb-like seta on distal margin. Maxilliped ( Fig. 3 View FIGURE 3 F) 4-segmented; proximal segment rod-like bearing conical, subterminal process on inner margin and single row of spinules on outer distal corner; middle segment fusiform bearing 2 setae and 3 patches of spinules; third segment shortest, bearing 1 seta and 1 pointed process; terminal claw curved, with spinulated inner margin covered with spinules and bearing 1 seta. Legs 1 to 4 as in female. Leg 5 ( Fig. 3 View FIGURE 3 C) with rod-like terminal segment, longer than wide 122 × 35, with length/width ratio of 3.46, slender than that of female. Leg 6 ( Fig. 3 View FIGURE 3 C) represented by 2 naked setae on posterolateral tip of genital flap.

Variability of measurement. Paratype males share all important morphological characters with the aollotype. Measurement range of their body parts and appendages of male type series (n = 3) was as follows: body (excluding caudal rami) length 1600–1735 (1679 ± 70), cephalothorax length 727–766 (751 ± 21), cephalothorax width 773–840 (801 ± 34), urosome length 498–629 (567 ± 66), genital somite length 168–203 (183 ± 18), genital somite width 211–227 (220 ± 8), anal somite length 75–83 (80 ± 5), anal somite width 122–137 (129 ± 7), caudal ramus length 93–95 (94 ± 1), caudal ramus width 50–55 (53 ± 2), caudal ramus length/width ratio 1.69–1.85 (1.77 ± 0.08), terminal segment length of leg 5 109–127 (119 ± 9), terminal segment width of leg 5 28–35 (32 ± 4), length/ width ratio terminal segment of leg 5 3.46–3.94 (3.78 ± 0.28).

Attachment site. In mantle cavity.

Remarks. The species of Anthessius can be separated into 2 groups according to the number of spines on the third exopodal segment of leg 4 of the female.The female of the new species has 3 spines on the terminal exopodal segment of leg 4. This condition is shared with the following 17 species, A. atrinae Suh & Choi, 1991 , A. dilatatus (Sars, 1918) , A. graciliunguis Do & Kajihara, 1984 , A. investigatoris Sewell, 1949 , A. kimjensis Suh, 1993 , A. leptostylis (Sars, 1916) , A. longipedis Ho & Kim, 1992 , A. lophiomi Avdeev & Kazachenko, 1986 , A. navanacis (Wilson, 1935) , A. nortoni Illg, 1960 , A. pinnae Humes, 1959 , A. placunae Devi, 1984 , A. projectus Kim, 1993 , A. proximus Stock, Humes & Gooding, 1963 , A. saecularis Stock, 1964 , A. sensitivus Stock, Humes & Gooding, 1963 , and A. varidens Stock, Humes & Gooding, 1963 . Nine species, namely, A. atrinae , A.dilatatus , A. graciliunguis , A. leptostylis , A. lophiomi , A. nortoni , A. pinnae , A. placunae , and A. saecularis , are distinctly separated from the new species by the caudal ramus longer than 3 times of the width (vs. 2 times longer than wide in the new species). Three species, A. kijimensis , A. navanacis , and A. projectus , are differentiated from the new species by the terminal segment of leg 5 oval and shorter than twice the width, and by the maxilla bearing more than 5 teeth (vs. terminal segment of the leg 5 about 2.5 times longer than wide, and the maxilla with 3 teeth in the A. isamusi n. sp.). Anthessius investigatoris , A. longipedis , Anthessius sensitivus differ from the new species by the elongate terminal segment of leg 5 longer than 3 times of the width. Anthessius varidense differs from the new species by the following characters: the antenna bearing a very small inner most apical claw and 3 subequal claws distally, and the maxilla carrying 5 teeth without protuberance (vs. the antenna bearing 2 strong, 1 long, and 1 small claws distally, and the maxilla bearing only 3 teeth). Anthessius proximus differs from the new species by the following characters: the antenna with 4 strong claws distally, and leg 5 with the rows of inconspicuous spinnules at the basis on each 2 distal spines (vs. the rows of spinnules existing distinctly at the basis of distal 2 spines on leg 5 in the A. isamusi n. sp.).

Etymology. The specific name of the new species, isamusi , is derived from an arbitrary combination of “Isamu Nakayoshi” and “musi”. Isamu-san is a crackerjack fisherman in Kumejima Island and also a collector of the specimens of T. marmoratus for this study. He also supported the KUMEJIMA 2009 in various ways. “Musi” is a generic term for small animals in Japanese. The name “ isamusi ” alludes to the new species as “Isamu’s animal”, and it is also his nickname. The name is used as noun in apposition.