Cirracanthus monacanthi Yamaguti 1939

Cirracanthus monacanthi (Yamaguti, 1939)

(Figs 1–2)

Taeniacanthus monacanthi Yamaguti 1939: 402; Shiino 1959: 372; Yamaguti 1963: 21. Cirracanthus monacanthi: Dojiri & Cressey 1987: 153; Dojiri & Ho 1987: 42.

Material examined. 1 Ƥ (WAM C38638), ex Chaetodermis penicilligerus (Cuvier) (WAM P.31950.001), Point Quobba, Western Australia, Australia, 13 April 1976; 1 Ƥ (AM P65262), ex Meuschenia trachylepis (Günther) (AM I42573-008), Port Stephens, New South Wales, Australia, 20 January 2000; 1 Ƥ (NSMT-Cr 21648), ex Monacanthus chinensis (Osbeck), Seto Inland Sea, Imabari, Ehime Prefecture, Japan, August 2005; 5 Ƥ, 1 3 and 1 copepodid (WAM C38643, C38711–C38712), ex 3 M. chinensis (WAM P.2139.001), Shark Bay, Western Australia, Australia, 1940; 25 Ƥ, 9 3 and 9 copepodids (WAM C38673–C38674, C38735), ex 2 M. chinensis (WAM P.25095.025), Exmouth Gulf, Western Australia, Australia, October 1974; 5 Ƥ (AM P65266), ex 1 M. chinensis (AM I41214-001), Lake Macquarie, New South Wales, Australia, 1 February 2000; 1 Ƥ (AM P65265), ex M. chinensis (AM I40864-011), White Bay, New South Wales, Australia, 17 May 2001; 1 Ƥ (AM P65264), ex M. chinensis (AM I20754-022), Lizard Island area, Queensland, Australia, 8 February 1979; 1 Ƥ and 1 3 (AM P65267), ex 1 M. chinensis (AM I41434-011), Port Hacking, New South Wales, Australia, 6 April 2000; 4 Ƥ (AM P65263), ex 1 M. chinensis (AM IA7819), Melville Island, Northern Territory, Australia, 1938; 1 Ƥ (AM P69680), ex M. chinensis (AM I20230-004), Cockburn Sound, Western Australia, Australia, 27 March 1978; 3 Ƥ (CAS 175285), ex 1 M. chinensis (CAS 207327), Gulf of Thailand, 5 April 1960; 18 Ƥ (CAS 175484), ex 1 M. chinensis (CAS 27547), Gulf of Thailand, 9 December 1968; 5 Ƥ (CAS 175466), ex 1 M. chinensis (CAS 36124), Java Sea, 5 December 1975; 1 Ƥ (MAGNT Cr014947), ex M. chinensis (MAGNT S.13273-005), Booby Island, Australia, 29 November 1991; 4 Ƥ (MAGNT Cr014949), ex 1 M. chinensis (MAGNT S.12962-001), Arafura Sea, 26 October 1990; 2 Ƥ (WAM C38679–C38680), ex 2 Paramonacanthus arabicus Hutchins (WAM P.32051.001), Persian Gulf, collection date unknown; 1 Ƥ (WAM C38580), ex Paramonacanthus choirocephalus (Bleeker) (WAM P.12091.001), Shark Bay, Western Australia, Australia, 1960; 10 Ƥ, 1 3 and 2 copepodids (WAM C38625, C38693–C38694), ex 3 P. choirocephalus (WAM P.23426.001), Learmonth, Western Australia, Australia, June 1973; 11 Ƥ and 2 copepodids (WAM C38559, C38629, C38639, C38719), ex 3 P. choirocephalus (WAM P.30239.003), Exmouth Gulf, Western Australia, Australia, 24 March 1991; 36 Ƥ, 1 3 and 4 copepodids (WAM C38579, C38612, C38647, C38689, C38701–C38702, C38754), ex 6 P. choirocephalus, Shark Bay, Western Australia, Australia, 1 March 2003; 8 Ƥ and 3 3 (WAM C38569, C38627–C38628, C38642, C38690), ex 5 P. choirocephalus, Shark Bay, Western Australia, Australia, 6 March 2003; 1 Ƥ (WAM C38615), ex Paramonacanthus filicauda (Günther) (WAM P.26220.002), Lacepede Island, Western Australia, Australia, 23 June 1978; 4 Ƥ (WAM C38609, C38652), ex 2 P. filicauda (WAM P.26701.001), Bomparte Archipelago, Western Australia, Australia, 31 January 1979; 4 Ƥ (AM P65270– P65271), ex 2 P. filicauda (AM I B2976), off Sydney, Australia, February 1953; 6 Ƥ (AM P65272), ex 1 P. filicauda (AM I21831 -026), Arafura Sea, 14 November 1980; 11 Ƥ (1 damaged) (AM P65273), ex 1 P. filicauda (AM I 34389-021), Island Head entrance, Queensland, Australia, 25 October 1993; 4 Ƥ (MAGNT Cr014955), ex 1 P. filicauda (MAGNT S.11794-007), North Cape Wessels, Northern Territory, Australia, 6 February 1986; 1 Ƥ (MAGNT Cr014956), ex P. filicauda (MAGNT S.13361-002), Arafura Sea, 28 October 1990; 72 Ƥ (4 damaged), 38 3 (2 damaged) and 16 copepodids (2 damaged) (WAM C38602, C38606, C38699–38700, C38727–C38731), ex 3 Paramonacanthus japonicus (Tilesius) (WAM P.32055.001), Sea of Japan, off Fukutsu, Fukuoka Prefecture, Japan, 13 September 1999; 10 Ƥ (1 damaged) (MAGNT Cr014957), ex 1 P. japonicus (MAGNT S.12989-001), Arafura Sea, 2 November 1990; 1 Ƥ (MAGNT Cr014958), ex P. japonicus (MAGNT S.13273-006), W. Booby Island, Queensland, Australia, 29 November 1991; 1 Ƥ (MAGNT Cr014959), ex P. japonicus (MAGNT S.14363- 005), NW Bassett-Smith Shoals, Western Australia, Australia, 12 June 1996; 10 Ƥ, 5 3 and 5 copepodids (AM P65275), ex 1 Paramonacanthus otisensis Whitley (AM I23883-001), Manly, New South Wales, Australia, 10 October 1976; 3 Ƥ (AM P65274), ex 1 P. otisensis (AM E1608), Fraser Island, Queensland, Australia, 29 June 1910; 15 Ƥ and 1 3 (AM P65277–P65279), ex 4 P. otisensis (AM I 25938-001), Point Quobba, Western Australia, Australia, April 1976; 1 Ƥ and 1 copepodid (AM P65276), ex 1 P. otisensis (AM I33364-002), Iluka, New South Wales, Australia, 15 February 1991; 5 Ƥ (NSMT-Cr 21649–21650), ex 2 Stephanolepis cirrhifer (Temminck & Schlegel), Seto Inland Sea, Itsukaichi, Hiroshima Prefecture, Japan, 11 November 2005; 8 Ƥ (NSMT-Cr 21656– 21657), ex 2 S. cirrhifer, Seto Inland Sea, Imabari, Ehime Prefecture, Japan, 1 May 2005; 3 Ƥ (NSMT-Cr 21655), ex 1 S. cirrhifer, Seto Inland Sea, Imabari, Ehime Prefecture, Japan, August 2005; 4 Ƥ (NSMT-Cr 21651), ex 1 S. cirrhifer, Seto Inland Sea, Imabari, Ehime Prefecture, Japan, 1 March 2006; 8 Ƥ (NSMT-Cr 21654), ex 1 S. cirrhifer, western North Pacific Ocean, Tosasaga, Kochi Prefecture, Japan, 18 June 2007; 1 Ƥ (WAM C38633), ex S. cirrhifer (WAM P.30260.020), Wakasa Bay, Japan, 10 November 1988; 1 Ƥ (WAM C38649), ex S. cirrhifer (WAM P.30055.021), Wakasa Bay, Japan, August 1989; 24 Ƥ (1 damaged) (WAM C38633, C38646, C38667–C38670, C38748), ex 4 S. cirrhifer (WAM P.30260.020), Wakasa Bay, Japan, 10 November 1988; 29 Ƥ (MAGNT Cr014963–Cr014964, Cr014966–Cr014968), ex 5 S. cirrhifer (MAGNT S.12729-014), Wakasa Bay, Japan, 10 November 1987; 2 Ƥ (CAS 175265), ex 1 S. cirrhifer (CAS 56599), Hong Kong, 20 August 1958; 2 Ƥ (CAS 175300), ex from 1 Stephanolepis hispidus (Linnaeus) (CAS 31459), Cape Colony, South Africa, 1934; 7 Ƥ (CAS 175276 and 175518), ex 2 Stephanolepis setifer (Bennett) (CAS 61084), Hong Kong fish market, 25 February 1958.

Supplemental description of adult female. Body 1.14 mm long (excluding caudal setae) and 0.56 mm wide (n = 3) (Fig. 1 A). Caudal ramus (Fig. 1 B) with 7 setae (seta I minute) and posterodorsal flap. Some specimens with 3 accessory teeth and lacking basal knobs on third segment of maxilliped (Fig. 1 C).

Description of adult male. Body 0.65 mm long (excluding caudal setae) and 245 µm wide (n = 8) (Fig. 1 D). Second pedigerous somite 168 µm wide; remaining pedigerous somites decreasing in width posteriorly. Genital double-somite longer (110 µm) than wide (84 µm). Abdomen 126 µm long and 55 µm wide; composed of 3 free somites. Caudal ramus longer (29 µm) than wide (15 µm), bearing similar elements as in female.

Mandible (Fig. 1 E) with 2 spinulate blades and small accessory seta. Maxilliped (Fig. 1 F–G) 4-segmented; first segment (syncoxa) two-thirds length of second segment (basis), bearing naked medial seta; basis elongate, armed with 2 proximomedial setae and longitudinal row of spinules on posteromedial and anteromedial surfaces; first endopodal segment small, unarmed; second endopodal segment represented by elongate claw, bearing long seta on posterior surface, 2 subequal setae on anterior surface and row of denticles along concave margin (denticles larger at proximal and distal ends). Legs 2 and 3 exopodal spines (only leg 2 exopod illustrated – Fig. 2 A) serrate along both margins, each bearing terminal flagellum. Spines on third endopodal segment of legs 2–4 (Fig. 2 B–D) serrate.

Attachment site. Branchial cavity wall.

Remarks. This species was originally described as Taeniacanthus monacanthi from Stephanolepis cirrhifer (Temminck & Schlegel) captured in the Seto Inland Sea off Tarumi, Japan by Yamaguti (1939). Dojiri & Cressey (1987) transferred T. monacanthi to their newly erected genus Cirracanthus based on the redescription of material collected from S. cirrhifer from Japan and Monacanthus chinensis (Linnaeus) from Hong Kong. Cirracanthus monacanthi and C. spinosus Dojiri & Cressey, 1987 are the only valid members of this genus (see Discussion section below for further details).

The specimens in the present study conform to the descriptions and illustrations provided by Dojiri & Cressey (1987). However, some female specimens examined in this study lacked basal knobs and had three accessory teeth on the maxilliped claw rather than one or two basal knobs and one or two accessory teeth as reported by Dojiri & Cressey (1987). Female C. monacanthi differs from C. spinosus in the shape of the mandibular accessory element (pyriform process vs. attenuate seta), presence of a distal process on the maxilliped basis, armature of the third exopodal segment of leg 3 (II, I, 4 vs. II, I, 5), shape of the third endopodal spines of legs 2 and 3 (stout and blunt vs. attenuate), absence of a terminal flagellum on each exopodal spine of leg 4 and the ornamentation pattern on the free exopodal segment of leg 5 (rows vs. patches). Additional differences include the relative length of the row of denticles on the maxilliped claw (denticles extending from near the base to the tip vs. row of denticles not extending to tip) and relative lengths of the third endopodal spines of leg 3 (innermost spine longest of three vs. middle spine longest of three) between the males.