Anuretes serratus Shiino, 1954

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 : 28

Anuretes serratus Shiino, 1954

( Figs. 10 , 11 )

Material examined. 1♀ in washings of cool box used to transport Prionurus microlepidotus Lacepède, 1804 (TC17609) and other fishes on 26 June 2016, QM Reg. No. W53048.

Site on host. Unknown.

Differential diagnosis. Cephalothorax dorsoventrally flattened with well-developed marginal membranes; about 1.07 times longer than wide; thoracic zone extending posteriorly about level with tips of lateral zones, not overlapping fourth pedigerous somite. Frontal plates lacking lunules. Fourth pedigerous somite visible in dorsal view ( Fig. 10A ). Genital complex with lateral margins evenly convex, posterior margin more-or-less transverse, with fifth legs visible at posterolateral corners in dorsal view; genital complex about 1.95 times wider than long and less than quarter length of cephalothorax; abdomen 1-segmented, not separated from genital complex by articulation. Caudal rami elongate, 2.9 times longer than maximum width, bearing only 5 caudal setae ( Fig. 10B ). Antennule ( Fig. 10C ) with 25 anteroventral setae and 2 dorsal setae on proximal segment; distal segment with 10 setae plus 2 aesthetascs plus posterior margin seta. Antenna with posteriorly-directed spinous process on proximal segment; middle segment unarmed; distal segment strongly curved, armed with proximal and distal setae ( Fig. 10D ). Post-antennal process with small tapering tine; associated papillae multisensillate. Maxillulary process bifid, inner lobe rounded, outer lobe pointed ( Fig. 10D ). Maxillary whip lacking. Maxilla ( Fig. 10E ) elongate. Maxilliped ( Fig. 10F ) slender, with bulbous lobe on concave margin of subchela. Sternal furca absent: ventral cephalothoracic surface with 2 pairs of rounded swellings anterior to intercoxal sclerite of leg 1 ( Fig. 11A ) and 1 pair anterior to intercoxal sclerite of leg 2 ( Fig. 11B ). Distal exopodal segment of leg 1 with 3 plumose setae on posterior margin; distal margin spine 1 longest; spines 2 and 3 each hand-like, with multiple digitiform processes ( Fig. 11A ); seta 4 just shorter than spine 1. Leg 2 ( Fig. 11B ) with 2-segmented endopod, compound distal segment bearing 8 setae: exopod 3-segmented; with outer spine on first segment directed obliquely across ramus and ornamented with large serrations; outer spine on second segment aligned with longitudinal axis of ramus plus inner seta; third segment with 2 outer spines, apical spine and 5 plumose setae. Leg 3 ( Fig. 11C ) with 2-segmented exopod; bearing large tapering outer spine and inner plumose seta on proximal segment; compound distal segment bearing 4 spines and 5 short plumose inner setae: endopod 2-segmented; first segment expanded to form velum, but lacking inner seta; distal segment with 6 setae. Leg 4 ( Fig. 11D ) uniramous, 3-segmented; first exopodal segment with outer spine, compound distal segment with 1 long and 3 short spines, all on oblique distal margin. Body length of adult female 2.60 mm.

Remarks. This distinctive species was originally described on the basis of three females collected from the body surface of Prionurus scalprum Valenciennes, 1835 (as Xesurus scalprum ) caught off Seto, Japan ( Shiino, 1954a). It was reported subsequently from Hawaii by Lewis (1964a) who redescribed the female and described the male for the first time. The host of the Hawaiian material was Naso hexacanthus (Bleeker, 1855) . The female from Moreton Bay was found in washings from a cool box used to transport freshly caught fish to the laboratory. This box had contained a mix of fish species caught by spear fishers (viz. one specimen each of Apogon limenus Randall & Hoese, 1988 , Canthigaster solandri (Richardson, 1845) , C. valentini (Bleeker, 1853) , Gerres sp. , Girella tricuspidata (Quoy & Gaimard, 1824) , and Microcanthus strigatus (Cuvier, 1831) and two specimens of Prionurus microlepidotus ). Given that this species of Anuretes has only been found on acanthurids and that its type host is Prionurus scalprum , it seems likely that this specimen had been dislodged from P. microlepidotus during transportation in the cool box.

Anuretes serratus displays an interesting array of unusual and unique features: it lacks a sternal furca but it has a bulbous lobe on the subchela of the maxilliped, spines 2 and 3 on the distal exopodal segment of leg 1 have multiple digitiform processes; leg 2 has a 2-segmented endopod due to the fusion of ancestral segments 2 and 3, and it carries a prominent serrated spine on the first exopodal segment of leg 2. In all of these characters and in other subtle details, the female from Moreton Bay conforms exactly to the original description ( Shiino, 1954a). There are, however, some differences when compared with the Hawaiian material. Firstly, the Hawaiian female genital complex has convex rounded posterolateral margins which serve to conceal the fifth legs in dorsal view and it has a very short abdomen that is about 2.5 times wider than long. In contrast, typical A. serratus has a straighter posterior margin to the genital complex, the prominent fifth legs are visible in dorsal view, and the abdomen is only about 1.5 times wider than long. The caudal rami, which have only 5 setae, are elongate (about 2.9 times longer than maximum width) in typical A. serratus whereas they are only about 1.5 to 1.6 times longer than wide in Lewis’s material. I consider the identity of the Hawaiian material to be in doubt, but the Moreton Bay female is in close agreement with A. serratus .

Figures

FIGURE 10. Anuretes serratus Shiino, 1954, female. A, habitus, dorsal; B, left corner of genital complex and abdomen, ventral view showing caudal rami and left fifth leg; C, antennule; D, antenna, post-antennal process, and bifidmaxillule,drawn in situ; E, maxilla; F, maxilliped. Scale bars:1.0 mm on A, 200 µm on B–E, 100 µm on F.

FIGURE 11. Anuretes serratus Shiino, 1954, female. A, leg 1, showing paired surface swellings anterior to interpodal bar; B, leg 2, showing surface swellings anterior to interpodal bar; C, leg 3, ventral; D, leg 4. All scale bars 200 µm.