Caligus coryphaenae Steenstrup & Lütken, 1861

Boxshall, Geoffrey A. & Bernot, James P., 2023, Resolving taxonomic and nomenclatural problems in the genus Caligus O. F. Müller, 1785 (Copepoda: Caligidae), Zootaxa 5360 (4), pp. 545-567 : 556

Caligus mordax Leigh-Sharpe, 1934 and

Caligus coryphaenae Steenstrup & Lütken, 1861

Caligus mordax was described by Leigh-Sharpe (1934) in his account of the commensal and parasitic Copepoda of the Siboga Expedition. Unfortunately, there are no published data on either the host or collection locality for this species. Only a single specimen was recovered and Leigh-Sharpe (1934) concluded that it was a female. Close examination of Leigh-Sharpe’s figures reveals two distinctive character states: firstly, there is no defined postantennal process, and secondly, the outer spine on the first exopodal segment of leg 3 has a particular spatulate shape and extends to the side of the ramus (i.e., it does not overlap onto the surface of the second segment). The same distinctive spine shape and orientation is exhibited by both sexes of C. coryphaenae and this species is also one of the very few species of Caligus that lack a defined postantennal process (cf. Kabata, 1979; Cressey & Cressey, 1980; Pillai, 1985; Ho & Lin, 2004). Careful comparison reveals that the specimen illustrated by Leigh-Sharpe (1934) is actually a male: the antenna bears an additional process on the subchela, the genital complex is small and rectangular, the free abdomen is 2-segmented, and legs 5 and 6 are represented by separate papillae each bearing setae, some of which are elongate. In the proportions of its 2-segmented abdomen and the configuration of its caudal rami, the illustrated specimen of C. mordax conforms closely to the male of C. coryphaenae as illustrated by Ho & Lin (2004: Fig. 82). We propose to recognise Caligus mordax Leigh-Sharpe, 1934 as a junior subjective synonym of Caligus coryphaenae Steenstrup & Lütken, 1861 .