Caligus oviceps Shiino, 1952

Boxshall, Geoff, 2018, The sea lice (Copepoda: Caligidae) of Moreton Bay (Queensland, Australia), with descriptions of thirteen new species, Zootaxa 4398 (1), pp. 1-172 : 96-98

Caligus oviceps Shiino, 1952

( Fig. 42 )

Syn: Caligus truncatogenitalis Roubal, 1981

Material examined. 1♀, 4 chalimus stages from Meuschenia trachylepis (Günther, 1870) (TC17598) 26 June 2016, QM Reg. No. W53088;1♀ from Kyphosus cinerascens (Forsskål, 1775) (TC17922) 5 July 2016, NHMUK 2017.295.

Site on host. Chalimus attached to fins, adult unknown (in body wash).

Differential diagnosis. Cephalothorax dorsoventrally flattened with well-developed marginal membranes along lateral zones of dorsal cephalothoracic shield; frontal plates with lunules. Genital complex not clearly demarcated from fourth pedigerous somite ( Fig. 42A ); about 1.06 times longer than wide; abdomen 1-segmented, about 1.30 times longer than wide; genital complex about 3 times longer than abdomen. Caudal rami about twice as long as wide. Antenna with blunt-tipped posterior process on proximal segment ( Fig. 42B ). Post-antennal process curved, associated papillae unisensillate. Posterior process of maxillule simple ( Fig. 42B ). Maxilla with ornamentation of denticles along distal margin ( Fig. 42C ). Maxilliped of female slender, with smooth myxal margin; claw on subchela short. Sternal furca with blunt-tipped, slightly incurved tines ( Fig. 42D ). Distal exopodal segment of leg 1 with 3 plumose setae on posterior margin; distal margin spine 1 slender, about as long as spines 2 and 3; spines 2 and 3 each with long accessory process; seta 4 longer than spines but shorter than segment ( Fig. 42E ). Leg 2 with marginal setules on endopodal segments 1, 2 and 3; outer spines on exopodal segments 1 and 2 aligned obliquely across surface of ramus ( Fig. 42F ); proximal outer spine on third segment short, naked, distal outer spine ornamented with expanded membrane on apical side only. Leg 3 without distinctive ornamentation on apron; exopod 3-segmented ( Fig. 42G ) first segment with short curved spine, lacking inner seta; second segment with outer spine and inner seta plus sensilla on dorsal surface; third with 3 spines and 4 plumose setae: endopod 2- segmented, with 0–1; 6 setal formula. Leg 4 uniramous, 3-segmented; exopodal segments with I, III spines; each spine with well-developed pecten ( Fig. 42H ). Body length of female 3.95 mm.

Remarks. Caligus oviceps was established by Shiino (1952) based on material taken from Siganus fuscescens (Houttuyn, 1782) in Japanese waters. This inadequately characterized species was fully redescribed by Lin et al. (1996a) and again by Ho & Lin (2004). The Moreton Bay females conform closely to these redescriptions in overall body proportions, shape of genital complex, and relative size and shape of the abdomen. Other similarities include: the relative weakly curved subchela of the antenna, the unisensillate papillae ornamenting the curved postantennal process, the ornamented distal margin of the maxilla, the shape of the sternal furca, the lengths and format of the distal setal elements on the exopod of leg 1, the relative length and position of the outer margin spines on the exopod of leg 2, and the curved outer spine of the first exopodal segment of leg 3 that does not reach the articulation with the second segment. In addition, the relative lengths of the 4 spines on leg 4 are the same. Caligus oviceps is a member of the C. macarovi -group.

Lin et al. (1996a) also confirmed that C. truncatogenitalis Roubal, 1981 was a junior subjective synonym of C. oviceps . Caligus truncatogenitalis was originally described based on a single female taken from Acanthopagrus australis caught off Coffs Harbour, only about 400 km south of Moreton Bay ( Roubal, 1981). The body length of female C. oviceps given by Shiino (1955b) was 3.41 mm and Roubal’s female (as C. truncatogenitalis ) was 3.54 mm ( Roubal, 1981). The female from Kyphosus cinerascens in Moreton Bay is slightly larger at 3.95 mm.

Detailed comparison between C. oviceps and C. latus Byrnes, 1987 reveals only relatively minor differences. They share numerous character states including: the configuration of the distal elements on the tip of the exopod of leg 1, the possession of unisensillate papillae associated with the post-antennal process, the shape of the flanged tines of the sternal furca, and the relative lengths of the spines on leg 4. There are minor differences in the shape of the female genital complex but these could possibly be attributed to the reproductive status of individual females. The distal margin of the brachium of the maxilla is ornamented with denticles in C. oviceps ( Fig. 42C ) but Byrnes (1987) did not figure this limb for C. latus and described it as “typical”. In the same paper, Byrnes did note the denticulate margin of the maxilla in C. dampieri and C. stokesi , indicating that he was aware of the significance of this character. It seems possible that C. latus Byrnes, 1987 is as a synonym of C. oviceps , but confirming this requires examination of the type material of the former.

In addition to the type host Siganus fuscescens , this copepod has been reported from Parupeneus chrysopleuron (Temminck & Schlegel, 1843) (as Pseudupeneus chrysopleuron ), Cheilodactylus quadricornis (Günther, 1860) (as Goniistius quadricornis ), Calotomus japonicus (Valenciennes, 1840) (as Leptoscarus japonicus ), Stephanolepis setifer Bennett, 1831 (as Monacanthus setifer ), Lethrinus haematopterus Temminck & Schlegel, 1844 , Girella punctata Gray, 1835 , Istiblennius edentulus (Forster & Schneider, 1801) (as Salarias enosimae ), and Entomacrodus stellifer Jordan & Snyder, 1902 (as Salarias stellifer ) in Japanese waters ( Shiino, 1959), and from Acanthopagrus australis and A. latus in Australia ( Roubal, 1981; Byrnes, 1987). Both Kyphosus cinerascens and Meuschenia trachylepis are new host records for C. oviceps and this is the first report of this widely distributed copepod from Queensland, although it was previously known from New South Wales.

Figures

FIGURE 42. Caligus oviceps Shiino, 1952, female.A, habitus, dorsal; B, antenna, post-antennal process and maxillule drawn in situ; C, tip of maxilla; D, sternal furca; E, distal segment of exopod of leg 1; F, outer margin spines of exopod of leg 2; G, exopod of leg 3; H, leg 4. Scale bars:1.0 mm on A, 200 µmon B,H, 100 µm on C, D, F, G, 50 µm on E.