Caligus spinosurculus Pearse, 1951

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 : 35-36

Caligus spinosurculus Pearse, 1951

This poorly described species belongs to the cluster of caligid species that share the following distinctive features in the female: bifid postantennal process and bifid posterior process of the maxillule, heavily ornamented apron of the third leg with an outer longitudinal row of spinules, an inner rosette of large spinules, and a prominent rib-like structure with a bifid apex, arising near the border with the intercoxal sclerite, a massive and strongly incurved spine on the first exopodal segment of leg 3, and a 3-segmented exopod on leg 4 armed with I,I,III spines. In the male the genital somite is slender and the short, two-segmented abdomen is as wide as the genital somite at its posterior margin. The list of nominal species sharing these features includes: C. chorinemi Krøyer, 1863 , C. tenax Heller, 1865 , C. aesopus Wilson, 1921 , C. spinosurculus , C. germoi Pearse, 1951 , C. rectus Pearse, 1952 , C. confusus , C. cordyla , C. zylanica Hameed & Pillai, 1986 and C. equulae Ho & Lin, 2003 . The close relationship between these species is supported by additional shared similarities including the relatively elongate distal segment of the antennule, the relatively long claw of the antenna and the weak development of the posterior process on the antenna, and the possession of a simple but strongly curved claw on the male antenna.

Caligus isonyx Steenstrup & Lütken, 1861 , as redescribed by Cressey (1991), is closely related to this cluster of species, sharing most of these character states, but it is excluded from consideration as it has a simple postantennal process and simple posterior process of the maxillule. Caligus fortis Kabata, 1965 also shares most of these character states including the bifid processes, but the inner rosette of spinules on the apron of leg 3 is less prominent and the rib-like structure is lacking, and the spine on the first exopodal segment of leg 3 is smaller and relatively straight, rather than strongly incurved. We exclude C. fortis from the further consideration.

Cressey (1991) redescribed Caligus chorinemi after re-examination of Krøyer’s holotype and listed C. tenax , C. germoi and C. rectus as new synonyms. Cressey presumably examined the holotype of C. rectus as the USNM registration number was cited in his account ( Cressey, 1991). Cressey noted that he had found C. chorinemi only on carangid fishes from the western Atlantic and that published records under the name C. tenax from the Indian and Pacific Oceans were of a related but different species. The relegation of C. germoi and C. rectus to synonymy is well supported by the similarities in descriptions of these species.

We do not accept Cressey’s (1991) treatment of C. tenax as a synonym of C. chorinemi . The key differences are the proportional lengths of the female genital complex and abdomen. The genital complex of female C. chorinemi is 1.3 to 1.4 times longer than the abdomen and the abdomen is about 2.9 times longer than wide (measured from Cressey, 1991: figure 198). In contrast, Heller’s (1865) figure shows the female genital complex of C. tenax as 2.8 times longer than the abdomen and the abdomen as only 1.5 times longer than wide. These are major differences and cannot be accounted for by intraspecific variability and we consider C. tenax a valid species, found in the western Atlantic.

The genital complex of adult female C. spinosurculus is nearly 3.5 times longer than the abdomen and the abdomen is 1.5 times longer than wide. We consider this falls within the range of C. tenax and propose to treat C. spinosurculus Pearse, 1951 as a junior subjective synonym of C. tenax Heller, 1865 . The relationship between C. tenax , the western Atlantic species, and the species that has been reported as C. tenax from Indo-Pacific fishes still needs to be resolved, as indicated by Cressey (1991).