Caligus stromatei Krøyer, 1863

Hayes, Polly, Justine, Jean-Lou & Boxshall, Geoffrey A., 2012, The genus Caligus Müller, 1785 (Copepoda: Siphonostomatoida): two new species from reef associated fishes in New Caledonia, and some nomenclatural problems resolved, Zootaxa 3534, pp. 21-39 : 36-37

Caligus stromatei Krøyer, 1863

Caligus stromatei was originally described based on material from Stromateus (rhomboides) collected in the Indian Ocean ( Krøyer, 1863). Krøyer (1863) provided illustrations of the habitus of both sexes, the antennule and lunule, the sternal furca, the rami of the third leg, and the fourth leg (1863: plate IV, figs. 1a–f). Other than mentions in lists or synthetic treatments such as Yamaguti’s (1963) compendium, this species has never been recorded since its original description.

Caligus multispinosus Shen, 1957 was described on the basis of females collected from Pampus argenteus (Euphrasen, 1788) [as Stromateoides argentus ] taken at Gwangtong, China ( Shen, 1957). It has been reported subsequently from the same host in Indian waters ( Pillai, 1961) and in Taiwan ( Ho & Lin, 2004). Ho & Lin (2004) noted that the specimens of “ Caligus rotundigenitalis Yü, 1933 ” reported from the gills of Pampus chinensis (Euphrasen, 1788) in Malaysia by Leong (1984) were misidentified: these specimens actually belonged to C. multispinosus .

Close comparison between Krøyer’s (1863) illustrations of C. stromatei and C. multispinosus as redescribed by Ho & Lin (2004) reveals detailed similarities. The abdomen of the adult female is elongate in both species—around 2.8 to 3.0 times longer than wide—and distinctly longer than the genital complex. The genital complex is just wider than long. The abdomen is described as two-segmented ( Pillai, 1985) or indistinctly two-segmented ( Ho & Lin, 2004) in C. multispinosus , but shown as one-segmented in C. stromatei , but the segmentation is not marked and we regard this as a difference in interpretation. The abdomen of the male is 2-segmented in both species, with the anal somite two to three times longer than the preceding somite. The outer spine on the first exopodal segment of leg 3 is straight and extends beyond the articulation with the second segment. Leg 4 has a stout protopodal segment and the exopodal spines are clustered together along the outer distal margin of the ramus. Krøyer (1863) only show two exopodal segments rather than three, but we consider this is an error. Krøyer (1863) does show two tiny knob-like processes on the outer margin of the first exopodal segment of leg 4. The distal knob-like process is located close to the end of the elongate pecten on the first exopodal segment and is more conspicuous: it is also figured by Pillai (1985) and by Ho & Lin (2004).

In the light of these similarities we here propose to treat C. multispinosus Shen, 1957 as a junior subjective synonym of C. stromatei Krøyer, 1863 .