Lernanthropus selenotoca, Boxshall & Bernot & Barton & Diggles & Q-Y & Atkinson-Coyle & Hutson, 2020

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 : 75-78

Lernanthropus selenotoca sp. nov.

( Figs. 40–41 )

Type material: Holotype ♀ and 3 paratype ♀♀ from Selenotoca multifasciata (Richardson, 1846) ( TC17225 ), Moreton Bay, Queensland; 18 January 2016; collected G.A. Boxshall; QM Reg. Nos. W29499 (Holotype ♀), W29500 (paratype ♀♀). 2 paratype ♀♀ from S. multifasciata ( TC17303 ), Moreton Bay, Queensland; 20 January 2016; collected by G.A.Boxshall; QM Reg. No. W29500. 2 paratype ♀♀ from S. multifasciata ( TC16942 ), Moreton Bay , Queensland; 08 December 2015; collected by S.C. Cutmore. 3 paratype ♀♀ from S. multifasciata ( TC17062 ), Moreton Bay , Queensland; 13 January 2016; collected G.A. Boxshall; NHMUK Reg. No. 2018.291–295.

Etymology: the name of the new species refers to the genus of the type host.

Description: Female body comprising cephalothorax and trunk ( Fig. 40 A–C). Body length of ♀ ranging from 3.32 to 3.74 mm, with a mean of 3.56 mm (based on 8 specimens). Cephalothorax about 1.15 times longer than wide, gradually becoming wider posteriorly; lateral margins linear, expanded into ventro-laterally directed folds on either side and extending anteriorly into slightly produced lobes, giving frontal margin a weakly indented appearance. Trunk about 1.1 times longer than cephalothorax; anterior part (second and third pedigerous somites) just wider than cephalothorax and bearing third legs posteriorly; posterior part (fourth pedigerous somite) covered by dorsal trunk plate; plate with evenly convex lateral margins, posterior margin with distinct median indentation. Urosome ( Fig. 41A ) comprising fifth pedigerous somite, genital complex and abdomen, all fused. Genital complex with conspicuous gonopores located dorsolaterally and with paired copulatory pores (arrowed in Fig. 41A ) located posterolaterally on ventral surface. Genital complex ornamented with 1 pair of sensillae and median pore on dorsal surface between gonopore openings. Paired caudal rami about 2.7 times longer than maximum width; not extending as far as posterior margin of dorsal trunk plate; each ramus armed with 2 plumose setae proximally on dorsal surface, 1 small lateral seta located at about 80% of ramus length, and 2 unequal apical setae ( Fig. 41A ).

Antennule ( Fig. 41B ) 6-segmented, some segments with irregular cuticular thickening; setal formula: 1, 3, 2, 0, 1, 10 + 2 ae. Parabasal flagellum ( Fig. 41C ) with swollen base and slender, slightly curved distal part. Antenna ( Fig. 41D ) robust, comprising massive corpus bearing papilliform element on medial surface, and distal subchela showing traces of suture line; subchela armed with small process proximally near articulation between corpus and subchela, plus 1 rounded and 1 pointed process; claw ornamented with surface striations and pits towards tip. Mandible styletlike, armed with 8 marginal teeth distally. Maxillule ( Fig. 41E ) bilobate, smaller inner lobe tipped with 1 spiniform element; larger outer lobe tipped with 3 unequal spiniform elements. Maxilla 2-segmented, comprising proximal syncoxa (lacertus) and distal basis (brachium); basis ( Fig. 41F ) ornamented with process distally on inner margin; terminal claw armed with sharp denticles along both margins. Maxilliped ( Fig. 41G ) 2-segmented, comprising massive corpus with papilliform element on myxal surface, and distal subchela; subchela comprising compound endopodal segment and strongly curved terminal claw; armed with distinctive accessory process on mid-concave margin.

Leg 1 biramous, members of leg pair joined by robust intercoxal sclerite ( Fig. 41H ): protopod inflated, armed with outer seta and inner spine; exopod 1-segmented, armed with 5 robust distal margin spines with minutely serrate margins; endopod 1-segmented, tapering distally, armed with terminal seta about as long as segment. Leg 2 ( Fig. 41I ) mounted on inflated hemispherical prominence derived from incorporated protopod and armed with outer seta on distinct papilla: both rami 1-segmented; exopod armed with 3 distal spines; endopod armed with pinnate apical seta, about 1.5 times longer than segment. Leg 3 uniramous, lacking exopod; endopodal lobe forming large shoehorn-shaped lamella, directed ventrally ( Fig. 40A, B ); leg pair separate medially; armed with outer basal seta on dorsal surface. Leg 4 ( Fig. 41J ) biramous, with rami forming elongate processes: outer (exopodal) lobe slightly longer than inner (endopodal); distal 35% of lobes extending beyond posterior margin of dorsal trunk plate; armed with basal seta proximally on dorsal surface. Leg 5 absent.

Male unknown.

Distribution: The type locality, Moreton Bay, is the only known locality for this species.

Remarks: The only previous record of a lernanthropid from Selentoca multifasciatus is that of Kabata (1979a) who reported L. gisleri from this host in Australia. No other lernanthropids have been reported from members of the family Scatophagidae .

In body proportions, the female of new species superficially resembles two species reported from carangid hosts in Indian waters, L. indicus and L. koenigii . In all three of these species the cephalothorax comprises about 25 to 30% of total body length, the anterior trunk is 1.0 to 1.2 times longer than the cephalothorax, and the dorsal trunk plate comprises about 40 to 45% of total body length and has a weak median indentation in its posterior margin. However, both of these Indian species have the fifth leg in the form of an elongate lobe while this leg is absent in L. selenotoca sp. nov. Most other species have a straight or evenly convex posterior margin on the dorsal trunk plate, unlike the medially indented margin of the new species.

Another unusual feature of the new species is the accessory process on the subchela of the maxilliped in the female. No other Indo-Pacific species (which has been described in sufficient detail) possesses such a process.

Figures

FIGURE 40. Lernanthropus selenotoca sp. nov., paratype ♀. A, habitus, ventral; B, habitus, lateral; C, habitus, dorsal. Scale bar 1 mm.

FIGURE 41. Lernanthropus selenotoca sp. nov., paratype ♀. A, urosome, dorsal view showing paired genital openings, copu- latory pores (arrowed) and caudal rami; B, antennule; C, parabasal flagellum; D, antenna; E, maxillule; F, basis of maxilla; G, maxilliped; H, leg 1 and intercoxal sclerite; I, leg 2; J, leg 4. Scale bars A, 200 μm, B,D,G,H, 100 μm, C,E,F, 50 μm, J, 0.5 mm.