Argulus quadristriatus Devaraj and Ameer Hamsa, 1977 (Figs 1–5)

Argulus quadristriatus Devaraj and Ameer Hamsa, 1977: 129–133, figs 1–11.

Material examined. 1 adult male and 2 adult females (NSMT-Cr 24635), ex Upeneus tragula Richardson ( Perciformes: Mullidae), in Iruka Channel (31°35′44.52″N, 130°33′48.96″E), Kagoshima Bay, Kyushu, Japan, 28 February 2016, leg. W. Miyazaki and Y. Kashiwagi; 1 adult female (KAUM-AT-289), collection data same as NSMT-Cr 24635; 1 developmental stage, male (NSMT-Cr 24636), ex Favonigobius reichei (Bleeker) ( Perciformes: Gobiidae) (BLIP 20050305 stored in Biological Laboratory), off mouth of Nagahama River (26°25′N, 127°44′E), Onna, Okinawajima island, East China Sea, Japan, 26 July 2005, leg. K. Abe; 1 developmental stage, female (RUMF-ZC-04356), ex Parupeneus ciliatus (Lacepède) ( Perciformes: Mullidae), Kin Bay off “Kaichu-doro” roadway (26°20′N, 127°55′E) connecting Okinawa-jima island to Henza-jima island, Japan, 2 May 2011, leg. S. Samejima.

Description of adult male. Body (Figs 1C, 2A) 6.00 long (n =1), comprising cephalon, four thoracic somites, and abdomen. Cephalon longer than wide, 4.30×3.44, bearing pair of compound eyes and nauplius eye, compound eye bean-shaped, 0.24 long, with medial cleft on posterior margin extending on posterior margin of second thoracic somite and pair of carapace lobes; ventral surface covered with pointed spinules on frontal region and lateral margins (Fig. 2B); respiratory areas composed of small, round anterior region and wedge-shaped posterior region (Fig. 2B). First to fourth thoracic somites covered with spinules on ventral surface (Fig. 2B); fourth thoracic somite bearing oval fleshy lobe posteroventrally (Figs 2B, 3H). Abdomen (Fig. 2A, B) bilobate, longer than wide, 4.17×2.33; each lobe with triangular posterior tip; caudal rami (Fig. 2C) located in cleft between lobes, rod-like, longer than wide, 0.04×0.03, with median constriction, each bearing five simple setae.

Antennule (Fig. 2D) 4-segmented; proximal segment robust, bearing pointed posterior spine; second segment robust, bearing curved hook-like anterior and terminal spines and pointed medial spine; third segment rod-like, bearing two distal setae; terminal segment rod-like, bearing seven distal setae. Antenna (Fig. 2D) 4-segmented; proximal segment robust, subdivided by constriction at mid-length, six setae and pointed process on proximal half and eight setae on terminal half; second segment bearing 13 setae; third segment bearing six setae; terminal segment bearing six distal setae. Postantennal spine (Fig. 2D) robust, with conical tip. Preoral stylet (Fig. 2E) slender, retracted in cuticular sheath. Mouth tube (Fig. 2E) elongate bearing 15 scales proximally. Mandible (Fig. 3A) bearing two blades with five and 13 teeth, respectively. Left maxillule (sucker) (Figs 2B, 3B) bearing 58 support rods, each composed of eight to eleven (rarely five or six) sclerites; right maxillule (sucker) bearing 61 support rods. Maxilla (Fig. 3 C–G) 5-segmented; proximal segment bearing basal plate with three pointed conical processes on posterior margin and circular patch composed of numerous scales and four setae (Fig. 3D); second segment rod-like, covered with setose scales (Fig. 3E), bearing seta on ventral surface and patch of squamate surface posteriorly (Fig. 3F); third segment rod-like, covered with setose scales and spatulate scales; fourth segment small, with patch of spatulate scales distally, bearing two setae (Fig. 3G); terminal segment with blunt tip, bearing two claw-like spines, six small spinules, and setose scale. Accessory spine (Fig. 3C) conical, situated adjacent to base of maxilla. Postmaxillary spine (Fig. 3C) conical.

Legs 1 to 4 (Figs 3H, I, 4 A–F) biramous, composed of coxa, basis, and both rami. Leg 1 (Figs 3H, I, 4A) elongate; coxa covered with spinules, bearing seta on ventral surface; basis small, covered with spinules; exopod unsegmented, elongate with 16 plumose setae on outer margin, two plumose distal setae, and nine plumose inner setae; endopod 3-segmented, bearing single simple and eight plumose setae on outer margin and nine plumose and two simple setae on inner margin of proximal segment, simple outer seta on middle segment, and three simple distal setae on terminal segment. Leg 2 (Figs 3H, 4B) elongate; coxa covered with spinules; basis small, covered with spinules; exopod elongate, unsegmented, with 12 plumose setae on outer margin, two plumose distal setae, and eight plumose inner setae; endopod unsegmented, with eight plumose setae on outer margin, two distal plumose setae, and eight plumose setae on inner margin. Anterior surface of coxae and bases of legs 3 and 4 modified as accessory sexual apparatus. Leg 3 (Figs 3H, 4C, D) elongate; coxa covered with spinules, bearing massive distal protuberance and distal foliate peg with serrate margin; basis small, partially covered with spinules, bearing massive protuberance and foliate peg with serrate margin; exopod elongate, unsegmented, with nine plumose setae on outer margin, two distal plumose setae, and eight plumose setae on inner margin; endopod 2-segmented, its proximal segment with four plumose setae on outer margin, six plumose and simple setae on inner margin, and terminal segment with seven plumose setae on outer margin, two distal plumose setae, and five plumose setae on inner margin. Leg 4 (Figs 3H, 4E, F) elongate; coxa bearing natatory lobe on posteroventral surface with five plumose setae; anterior surface of basis with two small lobes and large spherical swelling with scaly surface, posterior surface with four setae; exopod elongate, unsegmented, with nine plumose setae on outer margin, two distal plumose setae, and seven plumose setae on inner margin; endopod 2-segmented, bearing comprising proximal segment with four plumose setae on outer margin and single simple and six plumose setae on inner margin and terminal segment with six plumose setae on outer margin, two distal plumose setae, and six plumose setae on inner margin.

Description of adult female. Body (Figs 1D, 5A) 7.68– 10.59 long (n =4), comprising cephalon, four thoracic somites, and abdomen. Cephalon longer than wide, 6.19–9.00 (7.73±1.20)×4.18–6.03 (5.28±0.83), bearing pair of compound eyes and nauplius eye, compound eye bean-shaped, 0.23–0.29 (0.27±0.03) long, with medial cleft on middle of abdomen and pair of carapace lobes; ventral surface covered with pointed spinules on frontal region and lateral margins;; respiratory areas as in male. First to fourth thoracic somites densely ornamented with spinules on ventral surface; fourth thoracic somite bearing pair of posterolateral lobes dorsally (Fig. 5B). Abdomen (Fig. 5B) bilobate, longer than wide, 2.28–3.66 (3.04±0.57)×1.54–2.65 (2.12±0.48), bearing caudal rami. Caudal rami as in male, longer than wide, 0.05–0.07 (0.06±0.01)×0.03–0.04 (0.04±0.01).

General shape of antennule, antenna, other mouthparts, and thoracic legs 1 to 4 as in adult male, except as follows: exopod of leg 1 bearing knob-like process (Fig. 5C) (rudimentary flagellum) on outer margin with five plumose setae; coxa and basis of leg 3 and basis of leg 4 unmodified; natatory lobe of leg 4 well developed (Fig. 5D).

Developmental stage, male. General body shape and appendages as in adult male. Left maxillule (sucker) bearing 59 support rods composed of mainly five or six sclerites. Body 2.28 long (n =1). Cephalon longer than wide, 1.98×1.22. Compound eye 0.10 long. Abdomen longer than wide, 0.71×0.46. Caudal rami longer than wide, 0.03×0.02.

Developmental stage, female. General body shape and appendages as in adult female. Left maxillule (sucker) bearing 59 support rods composed of mainly five or six sclerites. Body 3.90 long (n =1). Cephalon longer than wide, 3.03×2.00. Compound eye 0.20 long. Abdomen longer than wide, 1.04×0.68. Caudal rami longer than wide, 0.03×0.02.

Coloration. Fresh specimens of both sexes with black pigmentation on dorsal surface of carapace and abdomen (Fig. 1C, D), concentrated into U-shaped, four long longitudinal, and three short horizontal lines. These lines still visible on specimens fixed in 99% ethanol (Figs 2A, 5A).

Infection sites. Body surface of host fish on head and on trunk near pectoral fin base.

Remarks. Argulus quadristriatus was originally described based on a single adult female from the body surface of a specimen of Psammoperca waigiensis (Cuvier, 1828) ( Perciformes: Latidae) collected in Palk Bay off Mandapam, southern India (Devaraj and Ameer Hamsa 1977). There are no significant differences in morphological features between the holotype female and the female specimens in this study, except for the mandible having two blades both with numerous fine teeth in the holotype (vs. five and 13 teeth) and an abnormally modified right leg four in the holotype (see Devaraj and Ameer Hamsa 1977; present study). Since some morphological features of the holotype were inadequately described or completely overlooked in the original description, re-examination of the holotype could reveal additional differences from the new Japanese material and provide insight into the variability of this species.

Newly proposed Japanese name for A. quadristriatus . He-kabui-umi-cho, meaning “a marine argulid coated by volcanic ash” in the dialect of Kagoshima, southern Japan, a place famous for the active volcano, Sakurajima, in Kagoshima Bay.