Caligus sclerotinosus Roubal, Armitage & Rohde, 1983

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 : 118-121

Caligus sclerotinosus Roubal, Armitage & Rohde, 1983

( Figs. 54 , 55 )

Syn: Caligus sp. Roubal 1981: 31–33pp., figs. 157–170.

Material examined. 1♀ from Acanthopagrus australis (Günther, 1859) (TC17580) 25 June 2016, QM Reg. No. W53109; 1♀ (TC17786), 0 1 July 2016, NHMUK Reg. No. 2017.322; 1♂ (TC17577) 25 June 2016, QM Reg. No. W53110.

Site on host. body surface.

Differential diagnosis. Cephalothorax extremely dorsoventrally flattened with well-developed marginal membranes along margins of lateral zones of dorsal cephalothoracic shield; frontal plates prominent, with large lunules. Genital complex broad, about 1.7 times wider than long, with conical fifth legs visible in dorsal view at posterolateral corners of complex ( Fig. 54A ); abdomen 1.4 times wider than long, only about 25% as long as genital complex. Antenna with broad spatulate posterior process on proximal segment ( Fig. 54B ). Post-antennal process with broad simple tine, associated papillae unisensillate. Maxillule with broad tine on posterior process, and smooth post-oral process ( Fig. 54C ). Maxilla with minute marginal ridges distally giving appearance of spinules in lateral view ( Fig. 54D ). Maxilliped slender, lacking myxal process. Sternal furca with short spatulate tines ( Fig. 54E ). Longitudinal ridges present on ventral cephalothoracic surface, either of sternal furca. Distal exopodal segment of leg 1 with 3 plumose setae on posterior margin; distal spine 1 shorter than spines 2 and 3, offset proximally; spines 2 and 3 each with accessory process; seta 4 naked, longer than spine but markedly shorter than segment. Leg 2 with endopodal segments 2 and 3 ornamented with marginal setules; outer spines on exopodal segments 1 and 2 lying obliquely across segment; proximal spine on third segment short, distal spine more than twice as long and unilaterally plumose ( Fig. 54F ). Leg 3 with 3-segmented exopod; first segment bearing short, blunt spine but lacking inner seta; second segment with outer spine and inner plumose seta; third with 3 outer spines and 4 plumose setae ( Fig. 54G ). Leg 4 uniramous, with long 2-segmented exopod armed with 1 lateral and 3 distal margin spines ( Fig. 54H ), each with elongate pecten near base. Leg 5 large, conical, projecting from posterolateral corner of genital complex: armed with single seta at base and 2 setae at tip. Mean body length of female 2.76 mm, range 2.73 to 2.78 mm (based on 2 specimens).

Male body length 2.31 mm, including caudal rami. Cephalothorax as in female, unusually flattened dorsoventrally and with prominent frontal plates ( Fig. 55A ). Genital complex with slightly convex lateral margins and with conspicuous paired fifth and sixth legs along posterior margin ( Fig. 55B ). Abdomen 1-segmented, about as long as wide, carrying paired caudal rami distally; anal slit terminal. Caudal rami with parallel sides, just longer than wide, measured at midpoints of margins. Each ramus armed with short plumose seta at inner distal angle, slightly longer seta at outer distal angle, small seta located just ventral to outer distal seta, and 3 long, plumose setae on distal margin.

Antennule, mandible, maxillule and maxilla as in female. Antenna modified ( Fig. 55C ); first segment elongate with marginal corrugations forming adhesion pad; second segment reflexed, elongate, bearing corrugated adhesion pads proximally and distally; distal segment forming short powerful claw, armed with 2 setae proximally. Maxilliped ( Fig. 55D ) with rounded myxal process on proximal segment (syncoxa) directly opposing tip of claw.

Legs 1 to 4 as in female.

Leg 5 ( Fig. 55B ) forming large conical process at posterodistal corner of genital complex, armed with outer protopodal seta proximally plus 2 plumose setae derived from exopod and originating in apical concavity. Leg 6 ( Fig. 55B ) represented by small process armed with 3 setae along distal and outer margins contiguous with genital operculum, closing off genital opening.

Remarks. This species was first reported and partly described by Roubal (1981) as Caligus sp. from Acanthopagrus australis caught at an unspecified locality on the coast of New South Wales (NSW). It was subsequently named by Roubal et al. (1983) after the discovery of additional material on another sparid host, Pagrus auratus (as Chrysophrys auratus ), taken off Coffs Harbour (NSW). Caligus sclerotinosus was redescribed by Ho et al. (2004) based on material from Pagrus major cultured in Japanese waters. The report and redescription by Ho et al. (2004) was the first record of this species from outside of Australian waters, but more recently it has also been reported as a serious pest of cultured P. major in Korea ( Venmathi Maran et al., 2012a) and a single female was found in a plankton tow taken near a fish farm in Japan ( Venmathi Maran & Ohtsuka, 2008). In 2014, C. sclerotinosus was reported from three species of Lutjanus Bloch, 1790 in Chamela Bay on the Pacific coast of Mexico ( Morales-Serna et al., 2014).

The extremely broad shape of the female genital complex with its conspicuous fifth legs located at the posterolateral corners is distinctive. The only other species with a genital complex of similar shape with a conspicuous fifth leg is C. praecinctorius Hayes, Justine & Boxshall, 2012 . This species was originally reported from New Caledonia on Gymnocranius grandoculis Valenciennes, 1830 , G. euanus (Günther, 1879) and Epinephelus fasciatus (Forsskål, 1775) (Hayes et al., 2012). Both species have the unusual longitudinal ridges on ventral cephalothoracic surface, either side of the sternal furca, and share many other detailed features. They can be distinguished by the broader genital complex which is 2.7 times wider than long in female C. praecinctorius compared to 1.7 times wider in C. sclerotinosus . The posterior border of the female genital complex is also much more strongly concave in the former species than in the latter. The specific epithet sclerotinosus refers to the “heavily sclerotized carapace” ( Roubal et al., 1983). Only the primary sutures on the dorsal surface of the cephalothoracic shield are shown in figures 54 and 55.

The male was described by Roubal et al. (1983): it has the same extremely flattened body form as the female and the fifth legs are conspicuously produced at the posterolateral corners of the genital complex. The Moreton Bay material of both sexes was collected from the original host reported by Roubal (1981), Acanthopagrus australis .

Figures

FIGURE 55. Caligus sclerotinosus Roubal, Armitage & Rohde, 1983, male. A, habitus, dorsal; B, genital complex and abdomen, ventral; C, antenna; D, maxilliped.Scale bars: 1.0 mm on A, 250 µm on B, 100 µm on C, D.

FIGURE54.Caligus sclerotinosus Roubal, Armitage& Rohde, 1983, female.A, habitus, dorsal; B, antenna and post-antennal process drawn in situ; C, maxillule and postoral process drawn in situ; D, tip of maxilla; E, sternal furca;F, exopod of leg 2; G, exopod of leg 3; H, leg 4. Scale bars:1.0 mm on A, 200 µmon B,C, H, 50 µm on D, E, 100 µm on F, G.