Mitrapus oblongus ( Pillai, 1964 )

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 : 79-82

Mitrapus oblongus ( Pillai, 1964)

( Fig. 39B , Fig. 42 )

Syn: Lernanthropus oblongus Pillai, 1964

Material examined: 15♀♀ and 5 ♂♂ (attached to ♀) from Herklotsichthys castelnaui (Ogilby, 1897) ( TC 17275), Moreton Bay, Queensland; 19 January 2016; collected by G.A. Boxshall; QM Reg. No. W29502. 1♀ and and 1♂ from H. castelnaui ( TC 17229), Moreton Bay, Queensland; 18 January 2016; collected by G.A. Boxshall; NHMUK Reg. No. 2018.296–297. 6♀♀ from H. castelnaui (as Harengula abbreviata ), Coffs Harbour, New South Wales; 15 May 1981; collected by M. La Spina; NHMUK Reg. No. 2018.298–301.

Differential diagnosis: Cephalothorax oval; anterolateral margins of cephalothorax folded downward to encircle base of antenna laterally. Trunk about 1.4 times longer than wide, covered with dorsal trunk plate extending posteriorly to overlap basal part of bilobed leg 4 ( Fig. 42 A–C); posterior margin of dorsal trunk plate entire and evenly convex. Anterior corners of trunk produced to form conspicuous, paired, knob-like protrusions. Lateral surfaces of trunk ornamented with numerous small papillae. Urosome comprising fifth pedigerous somite, genital complex and anal somite, all fused. Egg sacs linear. Caudal rami carried on ventral surface of abdomen; conical, tapering from broad base; about 1.5 times longer than width at base; armature comprising 2 large caudal setae located dorsally in proximal third, lateral seta located in mid-margin, plus 2 apical setae. Parabasal flagellum absent. Leg 2 biramous, with unimerous rami. Leg 3 bilobate with fleshy outer in inner lamellae; outer lamella orientated vertically, inner lobe shoehorn-like, partly fused along midline to other member of leg pair. Leg 4 bilobate; outer (exopodal) lobe elongate, inner (endopodal) lobe about half (42–52 %) of length of exopod; distal parts of both lobes protruding well beyond free posterior margin of dorsal trunk plate ( Fig. 42 A–C). Leg 5 absent. Body length of ♀ ranging from 1.87 to 2.13 mm, with a mean of 2.00 mm (based on 10 specimens). Body length of figured male 0.91 mm ( Fig. 39B ).

Distribution: This species was originally described (as Lernanthropus oblongus ) from India on the clupeid Sardinella fimbriata (Valenciennes, 1847) ( Pillai, 1964) . El-Rashidy & Boxshall (2009; 2010) recorded both sexes of M. oblongus from two clupeiform fishes caught in Mediterranean coastal waters off Alexandria ( Egypt): the dussumieriid Etrumeus teres (DeKay, 1842) which is an established immigrant species from the Red Sea, and Sardinella aurita Valenciennes, 1847 , a native Mediterranean clupeid. Romero & Öktener (2010) subsequently reported M. oblongus from the latter host in Turkish coastal waters. This is the first record of the genus from Australian waters and the clupeid host Herklotsichthys castelnaui constitutes a new host record for M. oblongus .

Remarks: Pillai (1985) commented that M. oblongus closely resembled M. rubiginosus ( Redkar, Rangnekar & Murti, 1949) (as L. rubiginosus ) collected from the clupeid Nematalosa nasus (Bloch, 1795) (as Chatoessus nasus ), but M. rubiginosus was subsequently recognised as a junior subjective synonym of M. heteropodus ( Yü, 1933) by El-Rashidy & Boxshall (2010). Both sexes of M. oblongus were redescribed in detail by El-Rashidy & Boxshall (2010).

Figures

FIGURE 39. Lernanthropus seriolii Shishido, 1898, adult ♀. A, urosome, dorsal view showing paired fifth legs, genital open- ings and caudal rami. Mitrapus oblongus (Pillai, 1964) ♂, B, habitus, dorsal. Scale bars A, 0.5 mm, B, 200 μm.

FIGURE 42. Mitrapus oblongus (Pillai, 1964) adult ♀. A, habitus, dorsal; B, habitus, lateral; C, habitus, ventral. Scale bar 1 mm.