Resolving taxonomic and nomenclatural problems in the genus Caligus O. F. Müller, 1785 (Copepoda: Caligidae) Author Boxshall, Geoffrey A. Department of Life Sciences, The Natural History Museum, Cromwell Road, London SW 7 5 BD, UK Author Bernot, James P. Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington DC, 20560, USA Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269, USA text Zootaxa 2023 2023-10-30 5360 4 545 567 https://www.mapress.com/zt/article/download/zootaxa.5360.4.5/52133 journal article 10.11646/zootaxa.5360.4.5 1175-5326 10084656 EA1BE6F9-88E2-4357-895E-8ED415206592 Caligus belones Krøyer, 1863 Material examined by R . F. Cressey : One female from Belone belone (Linnaeus, 1760) caught in the river Elbe , Germany and stored in the Smithsonian Institution , Washington D.C. , USA ( Reg. No. USNM 180596 ) . Supplementary Description: Genital complex of female about 1.2 times longer than wide and about 2.3 times longer than abdomen; genital complex with rounded posterolateral lobes; abdomen about 1.4 times longer than wide, with lateral swellings anterior to midlevel ( Fig. 1A ). Caudal rami about 1.6 times longer than wide. Antenna ( Fig. 1B ) with irregularly tapering posterior process on proximal segment; subchela armed with 2 setae located proximally and near anterior margin. Postantennal process ( Fig. 1B ) with small base and weakly curved tine. Posterior process of maxillule ( Fig. 1B ) strongly tapering towards acute tip. Sternal furca with widely divergent tines ( Fig. 1C ). Second exopodal segment of leg 1 ( Fig. 1D ) armed with 3 plumose setae along posterior margin; distal margin spines 1 to 3 each with accessory process; seta 4 more than twice as long as spine 1 and longer than segment. Leg 2 ( Fig. 1E ) with outer margin of second endopodal segment ornamented with setule row; first and second exopodal segments armed with outer spines directed obliquely across surface of ramus; third segment armed with II, I, 5. First exopodal segment of leg 3 ( Fig. 1F ) lacking inner seta; armed with short, slightly curved, outer spine ornamented with narrow flange along lateral margin, spine not reaching articulation separating second and third segments. Leg 4 ( Fig. 1G ) with 2-segmented exopod armed with I, IV spines, each with conspicuous pecten at base. FIGURE 1. Caligus belones Krøyer, 1863 adult female (body length 5.7 mm). A, habitus, dorsal; B, antenna, postantennal process and maxillule in situ , ventral; C, sternal furca; D, leg 1; E, leg 2; F, exopod of leg 3; G, exopod of leg 4. Remarks: Caligus belones has a complicated history. It was first described by Krøyer (1863) based on females collected from Belone belone (as “Hornfisk”) caught in Denmark . Later Wilson (1905) provided a redescription of a species he identified as C. belones but unfortunately Wilson’s species has a 2-segmented exopod on leg 4 with a spine formula of I, III whereas Krøyer (1863 : pl. VII, Fig. 1e ) shows the formula of C. belones as I, IV. The species described by Wilson (1905) was renamed C. wilsoni by Delamare Deboutteville & Nuñes-Ruivo (1958) in a paper which provided a partial redescription of true C. belones . Other partial descriptions are available (e.g. Cressey & Collette, 1970 ) but none provides the detail needed for the development of the online key.