Lernanthropus cadenati Delamare Deboutteville & Nuñes-Ruivo, 1954

Boxshall, Geoff A., Bernot, James P., Barton, Diane P., Diggles, Ben K., Q-Y, Russell, Atkinson-Coyle, Toby & Hutson, Kate S., 2020, Parasitic copepods of the family Lernanthropidae Kabata, 1979 (Copepoda: Siphonostomatoida) from Australian fishes, with descriptions of seven new species, Zootaxa 4736 (1), pp. 1-103 : 34-35

Lernanthropus cadenati Delamare Deboutteville & Nuñes-Ruivo, 1954

( Fig. 15 )

Material examined: 2♀♀ and 1 ♂ from Megalops cyprinoides (Broussonet, 1782) purchased at West End Market, Brisbane , Queensland, 25 February 2017; collected by R.Q-Y. Yong; QM Reg. No. W29484 . 2♀♀ from M. cyprinoides Darwin , Northern Territory, 18 October 2012; collected by B.K. Diggles; NHMUK Reg. No. 2018.214–215 .

Differential Diagnosis: Cephalothorax just wider than long ( Fig. 15A ); lateral margins produced anteroventrally into vertical flanges; frontal margin broad, slightly convex. Trunk subrectangular, comprising anterior part (second and third pedigerous somites) wider than cephalothorax and bearing third legs posterolaterally, and posterior part (fourth pedigerous somite) covered by dorsal trunk plate about as wide as anterior part. Dorsal trunk plate with weakly convex lateral margins but extremely short, so urosome entirely exposed and visible in dorsal view ( Fig. 15 A–C). Egg sacs linear. Caudal rami about 3.2 times longer than width at base. Parabasal flagellum with swollen base and tapering distal part. Leg 3 lamellate, with large fleshy outer lobe directed posteriorly and almost reaching to end of dorsal trunk plate, plus lamellate inner lobe (endopod): endopodal lobes fused in midline to form triangular ventral plate ( Fig. 15C ). Leg 4 bilobate, both lobes lamellate ( Fig. 15C ), outer lobe longer than inner with only very bases of lobes concealed beneath dorsal trunk plate. Leg 5 reduced to short conical process, unarmed. Mean body length of ♀ 5.05 mm, range 4.95 to 5.11 mm (based on 3 specimens).

Distribution. Delamare Deboutteville & Nuñes-Ruivo (1954) first described this species based on females collected from Elops senegalensis Regan, 1909 caught off the coast of Senegal (West Africa). It was subsequently reported from India on a megalopid, Megalops cyprinoides by Pillai (1966). Liu et al. (2009a) recorded it from the same host landed in Taiwan and they also found it on a second elopid host, Elops machnata (Forsskål, 1775) . In the collections of the NHM there is material of L. cadenati collected by J.-L. Justine from the gills of Elops hawaiensis Regan, 1909 caught off New Caledonia (NHMUK 2010.897). Ho & Sey (1996) reported L. cadenati from two sparid hosts, Acanthopagrus berda (Forsskål, 1775) and Sparidentex hasta (Valenciennes, 1830) (as Acanthopagrus hasta ). This report from sparid hosts, rather than elopid and megalopid hosts, is most unusual and needs confirmation. The present report is the first from Australian waters, and the known distribution now extends from Brisbane in Queensland to Darwin in the Northern Territory.

Remarks. Both sexes of this distinctive species were redescribed in detail by Liu et al. (2009a). The form of the third legs with their fused endopodal lobes, in combination with the short dorsal trunk plate which leaves the entire genitoabdomen and bases of the fourth legs exposed in dorsal view, are important diagnostic characters of the female. The male exhibits marked size disparity between its uniramous third and fourth legs: leg 3 is about as long as the male’s trunk while leg 4 is about 4 times longer than leg 3 and 1.5 times longer than the entire body of the male.

Lernanthropus delamari Capart, 1959 is also known from elopid hosts, E. senegalensis and E. lacerta Valenciennes, 1847 , from off the coast of Zaire and Senegal ( Capart, 1959; Diebakate & Raibaut, 1996). Lernanthropus cadenati can be differentiated from L. delamari by the extent of the dorsal trunk plate, which is short in the former, revealing the abdomen and caudal rami in dorsal view, but long in the latter, completely concealing the entire urosome in dorsal view. The single record of L. rathbuni Wilson, 1922 on Elops saurus Linnaeus, 1766 ( Causey, 1953) is questionable since, as already remarked by Diebakate & Raibaut (1996): L. delamari is very similar to L. rathbuni and the former was not recognized as a distinct species until 1959.

Figures

FIGURE 15. Lernanthropus cadenati Delamare Deboutteville & Nuñes-Ruivo, 1954, adult ♀. A, habitus, dorsal; B, habitus, lateral; C, habitus, ventral. Scale bar 2 mm.