Caligus epinepheli Yamaguti 1936

Caligus epinepheli Yamaguti, 1936

Syn: C. annularis Yamaguti, 1954 C. chiloscyllii Pillai, 1967

C. minutus Pillai, 1963

C. paxillifer Yamaguti, 1954

C. sciaenae Gnanamuthu, 1947 nec Caligus epinephali [sic]: Cressey, 1991

Differential diagnosis: Female genital complex and abdomen combined about 1.2 times longer than cephalothorax; body length 2.20–3.10 mm. Male body length 2.3 mm. Female genital complex without distinct postero-lateral lobes. Abdomen 2-segmented, first segment about twice as long as second. Male abdomen 2-segmented; first segment just shorter than second. Post-antennal process sexually dimorphic, larger and more strongly curved in male. Additional process present between post-antennal process and base of antenna in female. Sternal furca with slightly incurved tines. Female maxilliped with smooth medial margin. Male maxilliped with large pointed process on myxal margin, opposing tip of claw. Exopod of leg 1 with seta at inner distal angle longer than longest spine but shorter than segment; no vestiges of posterior margin setae; first exopodal segment broad, with strongly convex posterior margin. Outer margin of second endopodal segment of leg 2 ornamented with fine denticles. First exopodal segment of leg 4 with long spine reaching almost to tip of short outer margin spine on second segment, ornamented with marginal setule; all 3 distal margin spines on second exopodal segment differing in length, increasing towards terminal spine.

Material examined: 1 adult female collected from Epinephelus merra Bloch, 1793 caught off Green Island, Queensland, Australia by P.C. Young and identified by Z. Kabata: stored in collections of the Natural History Museum, London Reg. No. 1965.4.7.5.

Distribution: Indo-West Pacific; Japan, Taiwan, Malaysia, Australia.

Hosts: Carangidae: Scomberoides lysan (Forsskål, 1775) (as Chorinemus moadetta), Scomberoides tala

(Cuvier, 1832);

Drepaneidae: Drepane punctata (Linnaeus, 1758);

Hapalogenyidae: Hapalogenys mucronatus (Eydoux & Souleyet, 1850);

Hemiscyllidae: Chiloscyllium indicum (Gmelin, 1789);

Nemipteridae: Scolopsis vosmeri (Bloch, 1792);

Sciaenidae: Johnius dussumieri (Cuvier, 1830), J. glaucus (Day, 1876) (as Sciaena glauca), Pterotolithus

maculatus (Cuvier, 1830) (as Otolithes maculatus);

Serranidae Epinephelus septemfasciatus (Thunberg, 1793), Epinephelus akaara (Temminck & Schlegel,

1842), Epinephelus merra Bloch, 1793;

Sparidae: Acanthopagrus schlegelii (Bleeker, 1854).

Caligus epinepheli exploits a range of fish hosts, as summarised by Ho & Lin (2003).

Remarks: This species is extremely close to C. affinis in female body shape and proportions, especially the relatively short abdomen compared to the genital complex. We maintain it as a separate species on the basis of the difference in shape of the sternal furca, which has strongly incurved tines and a wide gape in C. affinis but only slightly incurved tines and a narrower gape in C. epinepheli. In addition the female postantennal process is weakly curved in C. epinepheli but strongly curved in C. affinis. There are also slight differences in the relative lengths of the distal spines on the fourth leg. The two subterminal spines are about equal in length and only slightly shorter than the terminal spine in C. affinis but all 3 distal spines differ in length in C. epinepheli, increasing in length towards the terminal spine. In this decision we are influenced by the known distribution patterns: C. affinis is only confirmed from the Mediterranean at present while C. epinepheli is an Indo-Pacific species unknown from the Atlantic.

Caligus epinepheli is a relatively small species with a reported female body length of 2.98–3.1 mm in Japan (Yamaguti 1936; Shiino 1952) and 2.20–2.26 in Taiwan (Ho & Lin 2004). This range is substantially smaller than the 4.5 mm length given by Pillai (1985) for material from Indian waters, and we consider that the specific identity of the material cited by Pillai requires verification.

Caligus chiloscyllii Pillai, 1967 is treated here as a synonym of C. epinepheli. The adult female has a similar body length (2.4 mm) and the proportional lengths of the cephalothorax, genital complex and abdomen (Pillai 1967) are similar to those of C. epinepheli. In addition the shape of the sternal furca, the degree of curvature of the female post-antennal process, the ornamentation on the lateral margin of the second endopodal segment of leg 2, and the relative lengths of the setal elements on the tip of the exopod of leg 1 and the spines on leg 4, are all similar to those described for C. epinepheli (Ho & Lin 2003). Although the original description (Yamaguti 1954) contained minimal detail, we also consider that C. annularis Yamaguti, 1954 does not differ from C. epinepheli in any significant characters. The female body length (2.1 – 2.4 mm) given by Yamaguti (1954) is in accord with the known size range for C. epinepheli and the sternal furca is the same shape.

Unfortunately C. sciaenae Gnanamuthu, 1947 is based only on the male and the description is inaccurate to the extreme that some figures are un-interpretable (Gnanamuthu 1947). However, it clearly belongs in the productus -group and its small body size (1.7 mm), the large, acutely-pointed myxal spine on the maxilliped, and the proportional lengths of the two abdominal somites, provide support for our proposed treatment of this species as a synonym of C. epinepheli.

Caligus paxillifer Yamaguti, 1954 is tentatively placed in synonymy with C. epinepheli, since it does not differ in any substantive characters from Yamaguti’s (1936) description. It shares the same body proportions, female body size, shape of sternal furca, even the relative lengths of the three spines on the exopod of leg 4. However, a detailed redescription of C. paxillifer is required to confirm this.