Lernanthropus paracruciatus, 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 : 61-67

publication ID	https://doi.org/ 10.11646/zootaxa.4736.1.1
publication LSID	lsid:zoobank.org:pub:970D7D36-6D8C-4463-B9EA-D3B8E191BE72
DOI	https://doi.org/10.5281/zenodo.3671109
persistent identifier	https://treatment.plazi.org/id/554BDB52-735D-FF8D-5FC9-FB6B2C6CF987
treatment provided by	Plazi
scientific name	Lernanthropus paracruciatus
status	sp. nov.

Treatment

Lernanthropus paracruciatus sp. nov.

( Figs. 30–34 View FIGURE 30 View FIGURE 31 View FIGURE 32 View FIGURE 33 View FIGURE 34 )

Type material: Holotype ♀, 4 paratype ♀♀, and allotype ♂ from Protonibea diacanthus (Lacepède, 1802) , Lorna Shoal, Timor Sea, Northern Territory, 22 August 2012; collected by D.P. Barton; MAGNT Reg. Nos. Cr019243 (Holotype ♀), Cr019244 (paratype ♀♀), Cr109245 (allotype ♂). 2 paratype ♀♀, 2 paratype ♂♂ from P. diacanthus, Vanderlin Island, Gulf of Carpentaria, Northern Territory, 27 February 2014; collected by D.P. Barton; MAGNT Reg. No. Cr 019246. 5 paratype ♀♀ from P. diacanthus , Cape Hotham, Northern Territory, 11 May 2014; collected by D.P. Barton; QM Reg. No. W29494. 1 paratype ♂ from P. diacanthus, Arafura Sea , Northern Territory, 25 July 2013; collected by D.P. Barton; QM Reg. No. W29495. 3 paratype ♀♀ from P. diacanthus, Lorna Shoal, Timor Sea , Northern Territory, 28 March 2014; collected by D.P. Barton; QM Reg. No. W29496. 1 paratype ♀ from P. diacanthus, Lorna Shoal, Timor Sea , Northern Territory, 02 October 2012; collected by D.P. Barton. 1 paratype ♀ from P. diacanthus, Arafura Sea , Northern Territory, 25 July 2013; collected by D.P. Barton. 1 paratype ♀, 1 paratype ♂ from P. diacanthus , Cape Hotham, Northern Territory, 30 August 2013; collected by D.P. Barton. 1 paratype ♂ from P. diacanthus, Vanderlin Island , Gulf of Carpentaria , Northern Territory, 26 February 2014; collected by D.P. Barton. 1 paratype ♂ from P. diacanthus, Vanderlin Island , Gulf of Carpentaria , Northern Territory, 27 February 2014; collected by D.P. Barton. 1 paratype ♀ and 1♂ from P. diacanthus, Groote Eylandt , Northern Territory, 15 October 2013; collected by D.P. Barton. 1 paratype ♀, 2 paratype ♂♂ from P. diacanthus, Darwin (Outer Harbour), Northern Territory, 07 March 2014; collected by B.K. Diggles. 1 paratype ♀ from P. diacanthus, Lorna Shoal, Timor Sea , Northern Territory, 02 December 2012; collected by D.P. Barton; NHMUK Reg. No. 2018.269–280.

Etymology: The species name alludes to the close resemblance between the new species and Lernanthropus cruciatus Pillai, 1962 .

Description of Female. Body slender, comprising cephalothorax and elongate trunk ( Fig. 30 View FIGURE 30 A–C): mean body length excluding fourth legs ranging from 5.27 to 6.54 mm, with a mean of 5.96 mm (based on 8 specimens). Cephalothorax about as long as wide, with small frontal region bearing antennules and antennae defined by marginal indentations; lateral margins more-or-less parallel, expanded into ventrolaterally directed folds on either side of cephalothorax; posterolateral corners of cephalothorax produced into slight lobes ( Figs. 30 View FIGURE 30 A–C, 34A–F). Anterior part of trunk nearly twice as long as cephalothorax, with linear lateral margins becoming gradually wider posteriorly: posterior part of trunk covered by dorsal trunk plate, typically about 1.3 times longer than wide and concealing entire fifth legs and caudal rami in dorsal view; dorsal trunk plate truncate, typically with nearly straight posterior margin ( Fig. 30A View FIGURE 30 ). Urosome comprising fifth pedigerous somite, genital complex and abdomen, all fused ( Fig. 31A View FIGURE 31 ); bearing paired, elongate caudal rami on ventral surface. Each caudal ramus about 7.5 times longer than maximum width; armed with 2 plumose setae on dorsal surface near base, minute lateral seta located subapically, plus 2 tiny apical setae ( Fig. 31A View FIGURE 31 ).

Antennule ( Fig. 31B View FIGURE 31 ) distinctly 7-segmented, proximal segment ornamented with long surface setules, some segments with irregular cuticular thickening; setal formula: 1, 3, 2, 1, 1, 2 + ae, 8 + ae. Parabasal flagellum located near of base of antennule, comprising broad base densely ornamented with long setules and curved distal part ( Fig. 31C View FIGURE 31 ). Antenna ( Fig. 31D View FIGURE 31 ) slender, comprising elongate corpus, bearing papilliform element proximally on medial surface, and short, strongly-recurved distal subchela; subchela armed with small process in zone of arthrodial membrane in articulation between corpus and subchela, plus small inner seta and blunt proximal process; terminal claw with striated and pitted areas on surface. Mandible stylet-like, armed with 8 marginal teeth distally ( Fig. 31E View FIGURE 31 ). Maxillule ( Fig. 31F View FIGURE 31 ) bilobate, smaller lobe tipped with 1 spiniform element; larger lobe tipped with 3 unequal spiniform elements. Maxilla 2-segmented: comprising proximal syncoxa (lacertus) and distal basis (brachium); basis ( Fig. 31G View FIGURE 31 ) with strong subapical spine and flaccid walled process adjacent to terminal claw; terminal claw ornamented with row of sharp denticles on both margins. Maxilliped ( Fig. 31H View FIGURE 31 ) 2-segmented comprising massive corpus with papilliform element proximally on medial surface, and distal subchela comprising compound endopodal segment and weakly curved terminal claw; subchela armed with proximal inner seta and distal spiniform process.

Leg 1 members joined by intercoxal sclerite ( Fig. 32A View FIGURE 32 ); protopodal part armed with outer seta on papilla and inner spine; outer and anterior surfaces of protopod densely ornamented with long setules, inner surface with tiny spinules; exopod 1-segmented, armed with 5 robust terminal spines with serrate margins and ornamented with patch of spinules on outer surface; endopod 1-segmented, tapering distally, armed with terminal spine about as long as segment and ornamented with spinules. Leg 2 ( Fig. 32B View FIGURE 32 ) mounted on inflated prominence derived from incorporated protopod and armed with outer seta on papilla; surface ornamented with long setules: both rami 1-segmented; exopod armed with 4 distal spines; endopod armed with robust apical element less than half length of segment, and ornamented with spinules distally. Leg 3 uniramous, with elongate endopodal lobe directed both laterally and posteroventrally, longer than anterior part of trunk; endopodal lobes separate along inner margin ( Fig. 30C View FIGURE 30 ); armed with dorsal outer basal seta; exopod not defined. Leg 4 ( Fig. 30C View FIGURE 30 ) biramous with both rami forming elongate processes, inner (endopodal) lobe slightly shorter than outer (exopodal) lobe, but both lobes damaged and incomplete in most specimens (cf. Fig. 34 View FIGURE 34 A–F); armed with basal seta dorsally near base of limb. Leg 5 represented by elongate lobe, about 10 times longer than wide; with unarmed tip but bearing single plumose seta dorsally near base ( Fig. 31A View FIGURE 31 ).

Male. Body smaller than female ( Fig. 32C View FIGURE 32 ), body length ranging from 2.20 to 2.58 mm, with a mean of 2.39 mm (based on 3 specimens). Cephalothorax comprising about 36% of total body length, broadest at middle, with evenly convex lateral margins: frontal area of cephalothorax carrying antennules and antennae, defined by marginal indentations. Trunk comprising fused pedigerous somites ( Fig. 32C View FIGURE 32 ) fused to unsegmented urosome incorporating genital complex and abdomen, bearing paired caudal rami. Caudal ramus elongate ( Fig. 32D View FIGURE 32 ), about 7.5 times longer than wide, armed with 2 plumose setae proximally on dorsal surface, 1 short lateral seta located in distal 17%, plus 2 apical setae; ornamented with single sensilla on dorsal surface.

Antennule 7-segmented ( Fig. 32E View FIGURE 32 ), setal formula: 1, 3, 2, 0, 1, 3 + ae, 7 + ae. Parabasal flagellum located close to base of antennule, comprising broad base with thickened cuticle plus slender distal part ( Fig. 32F View FIGURE 32 ). Antenna ( Fig. 32G View FIGURE 32 ) comprising long, slender corpus and distal subchela terminating in strongly recurved claw: corpus armed with broad process proximally on medial surface plus inner distal process; subchela armed with strong accessory claw proximally and another accessory claw near middle. Postantennal process rounded. Mandible stylet-like with 8 marginal teeth near apex ( Fig. 33A View FIGURE 33 ). Maxillule bilobate ( Fig. 33A View FIGURE 33 ); larger lobe armed with 3 unequal elements distally and ornamented with surface spinules; smaller lobe with strong apical element. Maxilla with strong spinous process subapically on basis ( Fig. 32H View FIGURE 32 ); distal claw with 2 rows of denticles. Maxilliped ( Fig. 33B View FIGURE 33 ) comprising robust corpus bearing small pointed myxal process and ornamented with patches of blunt spinules proximally on medial surface, and distal subchela armed with inner seta about at mid-length plus blunt process at base of terminal claw.

Leg 1 robust, members of leg pair joined by intercoxal sclerite ( Fig. 33C View FIGURE 33 ): basis armed with outer seta on papilla and stout inner spine with patch of spinules at base; exopod 1-segmented, broadening distally, armed with 5 distal spines, innermost spine longest with smooth margins, outermost spine short, middle 3 spines all robust, heavily sclerotized and apparently fused to segment: ramus ornamented with inner and outer patches of spinules; endopod elongate, 1-segmented, armed with spinulose apical seta just shorter than segment; segment extensively ornamented with spinules. Leg 2 ( Fig. 33D View FIGURE 33 ) retaining only slender vestige of intercoxal sclerite; basis with outer seta on papilla; both rami 1-segmented; exopod broad distally, armed with 3 small spines on outer part of distal margin, and ornamented with patches of spinules distally; endopod slender, slightly curved and armed with long spinulose seta apically; shorter than segment; surface ornamented with spinules. Leg 3 ( Fig. 32C View FIGURE 32 ) uniramous, forming long cylindrical process directed posterolaterally from ventrolateral origin on trunk: armed with dorsal basal seta at base of limb; surface of leg 3 smooth, unornamented. Leg 4 ( Fig. 32C View FIGURE 32 ) biramous, each ramus forming long cylindrical process, exopodal lobe longer than endopodal lobe: outer basal seta present dorsally at base of limb ( Fig. 32I View FIGURE 32 ). Leg 5 represented by minute papilla with apical seta (arrowed in Fig. 32I View FIGURE 32 ).

Distribution. The type locality of the new species is in the Northern Territory, but this species is also known from Broome and Wyndham in Western Australia (D.P. Barton, unpubl.).

Remarks: The new species is most closely related to L. cruciatus . Both species have a very long and well developed leg 3, characterized by an enlarged endopodal lobe projecting both laterally and posteroventrally, which is longer than the anterior part of the trunk (measured from the posterior margin of the dorsal cephalic shield to the shallow groove marking the origin of the dorsal trunk plate at the anterior edge of the fourth pedigerous somite). Both the new species and L. cruciatus also share numerous features with several other species found on sciaenid hosts and are similar to L. gisleri (see Table 3). These shared features include the following character states: the antennule is 7-segmented with the segment bearing the subapical aesthetasc separate from the apical segment; the proximal segment of the antennule is fused to a swelling on the surface of the cephalothorax and both segment and swelling are densely ornamented with long setules; the maxilla bears a curved process on the basis just proximal to the base of the apical claw; the protopod of leg 1 is ornamented with long setules; leg 3 is uniramous with the exopod forming a large, laterally-posteroventrally directed lamella; the rami of leg 4 are both elongate; leg 5 forms an elongate process; and the caudal rami are elongate. However, no other species listed in Table 3 have leg 3 as extremely elongate as in the new species and L. cruciatus .

The new species differs from L. cruciatus in the proportions of the dorsal trunk plate: in L. cruciatus the dorsal trunk plate is about 1.3 times longer than the anterior part of the trunk, whereas in L. paracruciatus sp. nov. it is only 1.0 to 1.1 times longer. The rami of leg 4 are also much longer relative to the dorsal trunk plate in the new species: in L. cruciatus the distal parts of the rami that extend beyond the rear margin of the dorsal trunk plate and are visible in dorsal view, are about one third of the length of the dorsal trunk plate, whereas in the new species the parts of the rami of leg 4 extending beyond the posterior margin of the plate (and visible in dorsal view) are about equal in length to the entire dorsal trunk plate.

The length to width ratio of the dorsal trunk plate is not a reliable character in this species because in fixed specimens it can sometimes be wrapped ventrally around the fourth legs and egg sacs (e.g. Fig. 34C View FIGURE 34 ) and thus appear much narrower than in other specimens (e.g. Fig. 30A View FIGURE 30 ). Examination of the large sample of material from P. diacanthus revealed that the posterior extremities of many specimens were profoundly damaged ( Fig. 34 View FIGURE 34 A–B, D–F). In many females the dorsal trunk plate was misshapen, to the point of being almost absent in some cases ( Fig. 34D View FIGURE 34 ), and in virtually every specimen examined one or more of the elongate leg rami was truncated or missing. Here we interpret this damage as due to the feeding activity of cleaner fish. It is important for taxonomists to be aware of the possibility of such damage since the relative lengths of the dorsal trunk plate and the rami of leg 4 have often been used as characters for species discrimination.

Sexual dimorphism is very marked in lernanthropids, affecting not only body form but also the structure and armature of almost every limb. However, the sexual dimorphism expressed in the first swimming leg of L. paracruciatus sp. nov. is unusual: the spines on the distal margin of the exopod have the normal tapering shape in the female but in the male these spines are thicker, have a more rounded shape and are contiguous (possibly fused).