Anthessiidae Humes, 1986

Hashimoto, Rina & Uyeno, Daisuke, 2023, First Specimen Based Record of Anthessius cucullatus (Copepoda: Cyclopoida: Anthessiidae) Associated with Aplysia spp. (Gastropoda: Aplysiida: Aplysiidae) from Coastal Waters of Kagoshima, Southern Japan, Species Diversity 28 (2), pp. 189-197 : 190-194

publication ID	https://doi.org/ 10.12782/specdiv.28.189
persistent identifier	https://treatment.plazi.org/id/67402376-A152-6F6A-FEFE-FEFB25001934
treatment provided by	Felipe
scientific name	Anthessiidae Humes, 1986
status

Treatment

Family Anthessiidae Humes, 1986 View in CoL

[Japanese name: Kaiyadori-kenmijinko-ka] Genus Anthessius Della Valle, 1880 [Japanese name: Kaiyadori-kenmijinko-zoku] Anthessius cucullatus Lee and Kim, 2021 [New Japanese name: Amenori-kenmijinko] ( Figs 1–5 View Fig View Fig View Fig View Fig View Fig )

Anthessius cucullatus Lee and Kim, 2021: 198–204 View in CoL , figs 8–11.

Materials examined. All specimens were collected from coastal waters of Kagoshima Prefecture, Japan: 2 females and 3 males, NSMT-Cr 31493, ex Ap . dactylomela (230 mm BL, n = 1), off Uranomae Port (31°35′36″N, 130°38′28″E), Sakurajima, at a depth of 30 m, 29 May 2021, leg. R. Hashimoto and D. Uyeno ; 1 female and 1 male, NSMT-Cr 31494, ex Ap . kurodai (182–234 mm BL, n = 4), off Kamoike (31°33′39″N, 130°33′50″E), at a depth of 1–2 m, 16 April 2021, leg. R. Hashimoto and D. Uyeno ; 1 female and 2 males, NSMT-Cr 31495, ex Ap . dactylomela (195–225 mm BL, n = 6), off Marukihama Beach (31°7′07″N, 130°12′42″E), Bonotsu, at a depth of 1–5 m, 16 July 2021, leg. R. Hashimoto, K. Nagayoshi, and D. Uyeno ; 3 females and 4 males, NSMT-Cr 31496, ex Ap . juliana (108–195 mm BL, n = 10), off Kamoike (31°33′39″N, 130°33′50″E), at a depth of 1–2 m, 16 February 2022, leg. R. Hashimoto, K. Nagayoshi, Y. Abe, H. Umeki, and D. Uyeno ; 24 females and 23 males, NSMT-Cr 31497, ex Ap . kurodai (133–211 mm BL, n = 2), off Bandokoro (31°14′49″N, 130°26′00″E), Wei, at a depth of 1–2 m, 29 April 2022, leg. R. Hashimoto, Y. Abe, H. Umeki, Y. Hatakeyama, N. Higashi, and D. Uyeno.

Adult female. Body ( Figs 1A View Fig , 5A View Fig ) cyclopiform, dark brown, 2.33–2.83 (2.65 ± 0.19) mm long (n = 4). Cephalothorax semilunar, wider than long, 610–920 (790 ± 130) × 1080–1390 (1230 ± 260) µm. Prosome dorsoventrally flattened, 1370–1710 (1550 ± 130) µm long. Urosome ( Fig. 1B View Fig ) 5-segmented, 950–1300 (1150 ± 120) µm long. Fifth pedigerous somite wider than long. Genital double-somite ( Fig. 1C View Fig ) wider than long, 260–310 (280 ± 20) × 390–450 (420 ± 20) µm, composed of wide anterior part and narrow posterior part, with hood-like dorsal lobe. Abdomen 3-segmented; first and second somites wider than long; anal somite almost as long as wide, 170– 250 (220 ± 30) × 180–230 (200 ± 20) µm. Caudal ramus ( Fig. 1D View Fig ) 1.78–2.32 (2.07 ± 0.21) times as long as wide, 160–210 (190 ± 20) × 90–100 (90 ± 4) µm, with one median setae on outer margin and five naked and one pinnate distal setae.

Rostral area ( Fig. 1E View Fig ) broad with rounded posterior margin. Antennule ( Fig. 1F View Fig ) 7-segmented, with armature formula: 4, 16, 5, 3, 4 + 1 aesthetasc, 2 + 1 aesthetasc, and 7 + 1 aesthetasc; all setae naked. Antenna ( Fig. 1G View Fig ) 3-segmented: first segment with one small seta distally; second segment with one small seta on inner margin; terminal segment with one short and three longer median setae on inner margin, and one long seta on posterior surface, two setae distantly outside and four unequal claws; innermost claw smallest, second inner claw robust and thicker than others, two outer claws thin, long. Labrum ( Fig. 2A View Fig ) bilobed, with delicate row of serrulation near distal tip. Mandible ( Fig. 2B View Fig ) with five elements on gnathobase: two stout bilobed processes (elements I and II); elongate distal lash (element III) bearing serrated outer margin and spinules on inner margin; small lobe (element IV) with serrated distal margin; elongate seta (element V) with fine spinules along inner margin. Maxillule ( Fig. 2C View Fig ) bilobate: inner lobe bearing two long and three small elements and comb-like process; outer lobe tipped with two small setae. Maxilla ( Fig. 2D View Fig ) 2-segmented; first segment unarmed; second segment bearing spinulose basal lobe, three large and four small spines, and one large spine in middle. Maxilliped ( Fig. 2E View Fig ) indistinctly 2-segmented, digitiform; distal segment tipped with small, point- ed process and additional seta.

Legs 1 to 4 ( Figs 2F, G View Fig , 3A, B View Fig ) biramous, composed of coxa, basis, and 3-segmented rami. Armature formula shown in Table 1. Inner coxal setae of legs 1 to 4 pinnate, long in legs 1 to 3 and short in leg 4. Outer basal setae of legs 1 to 4 naked. Inner margin of basis of legs 1 to 4 bearing marginal rows of cilia. Intercoxal sclerites of legs 1 to 4 unarmed. Leg 5 ( Fig. 3C View Fig ) 2-segmented: proximal segment bearing small dorsal seta; distal segment free, longer than wide, 180–230 (210 ± 20) × 70–110 (100) µm, length/width ratio of 2.10, bearing three spines and one small seta; inner margin and basis of spines bearing rows of spinules.

Adult male. Body ( Figs 3D View Fig , 5B View Fig ) cyclopiform, dark brown, 2.33–2.83 (2.65 ± 0.19) mm long (n = 5). Cephalothorax ovoid, wider than long 610–920 (790 ± 130) × 1080– 1390 (1230 ± 260) µm. Prosome elliptical, 1100–1810 (1470 ± 270) µm long. Urosome ( Fig. 3E View Fig ) 6-segmented, 950–1300 (1150 ± 120) µm long. Fifth pedigerous somite composed of narrow anterior and broad posterior parts. Genital somite ( Fig. 3D, E View Fig ) wider than long, 260–310 (280 ± 20) × 390–450 (420± 20) µm; genital flap with two apical elements. Anal somite almost as long as wide, 100– 240 (180 ± 50) × 140–220 (190 ± 40) µm. Caudal ramus ( Fig. 3E View Fig ) 1.78–2.32 (2.07 ± 0.21) times as longer than wide, 160– 210 (190 ± 20) × 90–100 (90 ± 4) µm.

Rostrum as in female. Antennule ( Fig. 4A View Fig ) as in female except second to fourth segments with formula as 15 + 3 aesthetascs, 6, and 3 + 1 aesthetasc. Antenna, labrum, mandible, maxillule, and maxilla as in female. Maxilliped ( Fig. 4B View Fig ) 3-segmented with terminal claw; proximal segment (syncoxa) rod-like bearing conical process on inner margin and patch of spinules distally; middle segment (basis) with two inner setae and patch of numerous fine spinules on inner surface; distal segment (endopod) bearing one long seta and one pointed process; terminal claw bearing one basal seta and marginal row of spinules along inner margin.

Leg 1 as in female, except third endopodal segment bearing armature formula: I, I, 4. Legs 2 and 3 as in female ( Fig. 4C View Fig ). Leg 4 as in female, except third inner spine on third endopodal segment curved ( Fig. 4D View Fig ) (vs. straight in female). Leg 5 ( Fig. 4E View Fig ) basically as in female, slightly slender, 150– 190 (160 ± 10)× 60–80 (70 ± 9) µm, length/width ratio of 2.38.

Infection sites. Body surface, especially on the inner side of the mantle and around the gills. Some males were found attached to the urosomites of the females using the maxillipeds ( Fig. 5C View Fig ).

Remarks. Anthessius cucullatus is clearly differentiated from other 47 congeners by having the unique hood-like dorsal lobe reaching to the posterior margin of the genital double-somite in the female ( Lee and Kim 2021). The species is also differentiated by other characters from the congeners. Twenty species of the genus including An. cucullatus , have three spines on the third exopodal segment of leg 4, whereas the remaining 27 species have four spines ( Lee and Kim 2021). Of those 20 congeners, An. cucullatus shares short caudal rami (i.e., less than three times long as wide) with the following 11 species: An. dolabellae Humes and Ho, 1965 , An. investigatoris Sewell, 1949 , An. isamusi , An. kimjensis Suh, 1993 , An. longipedis Ho and Kim, 1992 , An. lophiomi Avdeev and Kazachenko, 1986 , An. navanacis ( Wilson, 1935) , An. placunae Devi, 1984 , An. proximus Stock, Humes, and Gooding, 1963 , An. sensitivus Stock, Humes, and Gooding, 1963 , and An. varidens Stock, Humes, and Gooding, 1963 (see Wilson 1935; Sewell 1949; Stock et al. 1963; Humes and Ho 1965; Devi 1984; Avdeev and Kazachenko 1986; Ho and Kim 1992; Suh 1993; Uyeno and Nagasawa 2012; Lee and Kim 2021).

Anthessius cucullatus differs from the following six congeners: An. kimjensis , An. longipedis , An. lophiomi , An. navanacis , An. placunae , and An. sensitivus by having a small basal lobe armed with minute spinules on the maxilla (vs. unarmed) (see Wilson 1935; Illg 1960; Stock et al. 1963; Devi 1984; Avdeev and Kazachenko 1986; Ho and Kim 1992; Suh 1993). Anthessius cucullatus differs from An. isamusi by having the antenna bearing four unequal claws: the innermost claw is much smaller than others; the secondinner claw is thicker and larger than others and one long seta on the posterior surface, and two setae at outer distal corner. The antenna of An. isamusi bears two strong hook-like, one long, and one small claws and two long setae (see Uyeno and Nagasawa 2012). Anthessius cucullatus is separated from An. investigatoris , An. proximus , and An. varidens by the third endopodal segment of leg 4 in the male bearing a curved inner spine whereas that of the three species are not transformed (see Sewell 1949; Stock et al. 1963; Humes and Ho 1965). Anthessius cucullatus shares many characters with An. dolabellae but it differs from the latter by having the distal segment of leg 5 lacking fine spinules, because that of An. dolabellae has the outer margin ornamented with spinules (see Humes and Ho 1965).