Lernanthropus abitocephalus Tripathi, 1962

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 : 17

Lernanthropus abitocephalus Tripathi, 1962

( Fig. 7 A–B)

Material examined: 3♀♀ from Pomadasys argenteus (Forsskål, 1775) , Bynoe Harbour, Darwin , Northern Territory, 24 November 2012, collected by B.K. Diggles ; 2♀♀ to MAGNT Reg. No. Cr 019240 ; 1♀ QM Reg. No. W29477 . 2♀♀ (1 incomplete) from P. argenteus, Adelaide River , Northern Territory, 28 August 2012, collected by B.K. Diggles ; NHMUK Reg. No. 2018.230 . 2♂♂ from P. argenteus, Bynoe Harbour , Northern Territory, 16 October 2014, collected by B.K. Diggles ; 1 ♂ MAGNT Reg. No. Cr 019240 ; 1 ♂ NHMUK Reg. No. 2018.232 . 1 immature ♀ (incomplete) from P. argenteus, Inner Harbour , Northern Territory, 25 August 2012, collected by B.K. Diggles ; NHMUK 2018.231 .

Differential diagnosis: Cephalothorax much longer than wide, narrowing anteriorly towards short transverse frontal margin ( Fig. 7A ). Anterior part of trunk (second and third pedigerous somites) just longer and wider than cephalothorax, becoming gradually wider towards posterior part (fourth pedigerous somite) covered by dorsal trunk plate. Dorsal trunk plate very wide, with straight transverse free posterior margin. Urosome comprising partly fused fifth pedigerous somite, genital complex and abdomen ( Fig. 7B ). Paired caudal rami elongate, each ramus about 2.5 times longer than wide; tapering towards blunt apex. Parabasal flagellum tapering linear process, about half length of antennule. Leg 3 forming fleshy lamella, outer lobe splayed outwards at right angle to longitudinal axis of body and extending towards posterior; inner lobe forming vertical lamella close to midline. Leg 4 bilobate; inner lobe shorter than outer; both lobes with distal tips protruding beyond free posterior margin of dorsal trunk plate. Leg 5 represented by unarmed conical process. Mean body length of ♀ 1.88 mm (range 1.82 to 1.92, based on 4 speci- mens); body length of ♂ specimens 1.31 and 1.34 mm.

Distribution: This species was originally described on the basis of females collected from Pomadasys maculatus (Bloch, 1793) caught in the Bay of Bengal, India ( Tripathi, 1962). Song & Chen (1976) subsequently recorded L. abitocephalus on Pomadasys sp. in Chinese waters. This is the first record from Australia and P. argenteus is a new host record.

Remarks: Pillai (1985) found L. abitocephalus on P. maculatus caught off Kerala and redescribed it based only on the female. He made comparisons with L. pomadasysis described from the same host in Indi- an waters by Rangnekar & Murti (1961) and concluded, despite some differences which he attributed to mistakes by Rangnekar & Murti, that these two species are synonymous. Inexplicably Pillai (1985) chose to relegate the older of the two names ( L. pomadasysis ) to synonymy with the younger name ( L. abitocephalus ). Ho et al. (2008) redescribed female L. pomadasysis and described the male for the first time. They noted significant differences from L. abitocephalus in the proportions and shape of the cephalothorax, in the form of leg 3 and in the relative lengths of the lobate rami of leg 4. On the basis of these differences (cf. Fig. 7 C–D), they resurrected L. pomadasysis as a valid species, distinct from L. abitocephalus . We follow their treatment here.

Another closely related species is L. villiersi Delamare Deboutteville & Nuñes-Ruivo, 1954 which is also parasitic on pomadasyids: it was first reported from Pomadasys incisus (Bowdich, 1825) (as Pristipoma bennetti Lowe ) and P. rogeri (Cuvier, 1830) (as Pristipoma suillus (Valenciennes)) caught in the southeastern Atlantic off the coast of Senegal ( Delamare Deboutteville & Nuñes-Ruivo, 1954). Its known range was extended south to a latitude of 25° S by Capart (1959) who also reported it from P. incisus . An additional host, P. peroteti (Cuvier) , was later reported from off the coast of Senegal ( Diebakate & Raibaut, 1996). The shape of the cephalothorax of L. villiersi is somewhat intermediate between L. abitocephalus and L. pomadasysis , and the posterior margin of the dorsal trunk plate is weakly indented in L. villiersi but straight in the other two species.As noted by Pillai (1985), the record of L. villiersi on Sillago sihama (Forsskål, 1775) caught off Sri Lanka ( Kirtisinghe, 1964) may well be a misidentification of the very similar L. sillaginis Pillai, 1963 .

Figures

FIGURE 7. Lernanthropus abitocephalus Tripathi, 1962, adult ♀. A, habitus, dorsal; B, urosome plus caudal rami, dorsal. Lernanthropus pomadasysis Rangnekar & Murti, 1961, adult ♀. C, habitus, dorsal; D, urosome plus caudal rami, dorsal. Scale bars A, C, 0.5 mm; B,D, 200 μm.