Paraplatyarthrus pallidus Javidkar and King

Javidkar, Mohammad, King, Rachael A., Cooper, Steven J. B., Humphreys, William F. & Austin, Andrew D., 2017, Taxonomy of Paraplatyarthrus Javidkar and King (Isopoda: Oniscidea: Paraplatyarthridae) with description of five new species from Western Australia, and comments on Australian Trichorhina Budde-Lunde, 1908 (Platyarthridae), Zootaxa 4243 (3), pp. 401-431 : 422

Paraplatyarthrus pallidus Javidkar and King , sp. nov.

Figs 17–19 , 2 G, 20B

urn:lsid:zoobank.org:act:149ADE06-BD8E-4517-A3D4-F3A2182CEEF8

Type material. Holotype: Male, WAM C 54803 (BES15545.2), Lake Miranda East calcrete aquifer, Yakabindie pastoral station, Eastern Murchison region , Western Australia, Australia; 27.66405°S, 120.61015°E, Jul 2010, coll. S.J.B. Cooper & W.F. Humphreys.

Paratypes: Lake Miranda East : 2 females ( WAM C 54804, BES15545.8; WAM C 54805, BES15545.3) , 3 males ( WAM C 54806, BES15545.11; WAM C 54807, BES15545.10; WAM C 54808, BES15545.6) (same locality and collection data as holotype) , 1 female (WAM C 66909, BES15543.3), 1 male (WAM C 66910, BES17215.2), 27.66384°S, 120.61076°E, May 2012, coll. S.J.B. Cooper & W.F. Humphreys. Lake Miranda West (same calcrete as holotype): 2 males ( WAM C 66897, BEST 15538.2 ; WAM C 66898, BES15538.3) , 2 females (WAM C 66899, BES15538.14; WAM C 66908, BES15538.10), 27.74667°S, 120.5266°E, Jul 2010, coll. S.J.B. Cooper & W.F. Humphreys.

Diagnosis. Single significantly reduced black ommatidium-like component (vestigial) with no eye structure. Body pale. Maxilla 2 with no delimiting line between lobes, inner lobe contracted into small area in distal inner apical corner. Uropodal sympodite with incision on outer margin, apically truncated and merging with proximal sympodite. D/C ratio is relatively constant in tergites 1–7, except for one next to lateral margin in tergite 7.

Description. Male (WAM C 54803), Body length 2.7 mm, completely pale ( Fig. 2 G). Cephalon lateral lobes small, with straight sides. Eyes significantly reduced, with only 1 dark ommatidium-like component (vestigial) with no external eye structure. Antenna 1 medial article shortest, distal article longest, seemingly bearing 6 aesthetascs on top ( Fig. 17 A). Antenna 2 flagellum with basal article short, about 1/3 of distal one. Left mandible ( Fig. 17 B) pars molaris with about 8 plumose setae; hairy lobe bearing 2 plumose setae, with no small fine setae. Right mandible pars molaris with probably more than 4 plumose setae; 1 plumose seta on hairy lobe. Maxilla 1 outer endite ( Fig. 17 C) with outer group of 4 teeth covering about 65% of marginal area, inner group of 2 cleft, 2 simple and 1 truncated tooth; inner endite ( Fig. 17 D) with 3 fine setae on subapical outer marginal corner. Maxilla 2 ( Fig. 17 E) not apically bilobate (delimiting line hardly recognisable); inner lobe contracted into small area on distal inner corner. Maxillipedal endite ( Fig. 17 F) with 1 large seta close to subapical inner corner; distal articles of palp with 1 large proximal seta, medial tuft of 2 or 3 simple setae and apical tuft of few long setae.

Epimeron 1 bluntly projected anteriorly. In dorsal view, posterolateral corner of pereonites 1–4 rounded. Posterolateral corner of pereonites 5–7 posteriorly directed ( Fig. 20 B). Pleonite 5 posterior corner reaching uropod sympodite but not surpassing it. with Noduli laterales at approximately same distance from posterior margin in tergites 2–7; D/C ratio is relatively constant in tergites 1–7, except for one next to lateral margin in tergite 7 (Appendix 2).

Pereopod 1 carpus inner side with long simple and serrate setae, tuft of fine setae present medially near distal margin ( Fig. 18 A); propodus with both small simple and large serrate setae; dactylus with long seta exceeding claws, outer claw relatively straight. Pereopod 7 carpus not showing sexual dimorphism ( Fig. 18 B). Pleon outline continuous with pereon. Pleopod 1 endopodite ( Fig. 19 A) moderately acute, with narrow spermatic furrow and few very fine setae close to distal part; exopodite ( Fig. 19 B) with no marginal setae, posterior point not developed. Genital papilla ventral sheath apically pointed and surpassed by long rounded-tip lobe ( Fig. 19 A). Pleopod 2 endopodite ( Fig. 19 C) long and very slender closer to distal end. Pleopod 2–5 exopodites with 3 to 4 medium to large simple and serrate setae ( Fig. 19 D–G). Pleotelson pointed. Uropodal exopodites surpassing pleotelson; endopodites slightly exceeding pleotelson; sympodite with extended incision and truncated apex linking proximal and distal sympodite ( Fig. 18 C).

Etymology. The new species name is taken from the Latin ‘pallidus’ alluding to its pale body.

Remarks. Paraplatyarthrus pallidus sp. nov. has a minimum COI divergence of 16.5% from the described Paraplatyarthrus species (Appendix 1). Paraplatyarthrus pallidus is easily distinguished based on having only 1, significantly reduced, pale dark ommatidium-like component (vestigial) with no external eye structure, a pale body, Maxilla 2 not apically bilobate (delimiting line hardly recognisable), and the incision on the uropod sympodite merging with the proximal sympodite. The body length varies between 2.7 mm and 4.0 mm. This species was referred to as Taxon 4 in Javidkar et al. (2015). It is restricted to the Lake Miranda East/West calcrete, Yakabindie pastoral station, Eastern Murchison region, Western Australia.

Figures

FIGURE 2. A: P. crebesconiscus sp. nov.; B & C: P. cunyuensis sp. nov., the arrow shows the cephalic lateral lobe; D: P. nahidae sp. nov.; E & F: P. occidentoniscus sp. nov., the arrow shows the cephalic lateral lobe; G: P. pallidus sp. nov.; H: P. subterraneus; scale bar of the image c: 0.5 mm, scale bar in other images: 1 mm. All images are of paratype specimens.

FIGURE 17. Paraplatyarthrus pallidus sp. nov., (Holotype, ♂), A, antenna 1; B, left mandible; C, maxilla 1 outer endite; D, maxilla 1 inner endite; E, maxilla 2; F, maxilliped. Scale bars: 0.1 mm.

FIGURE 18. Paraplatyarthrus pallidus sp. nov., (Holotype, ♂), A, pereopod 1; B, pereopod 7; C, uropod (Paratype). Scale bars: 0.1 mm.

FIGURE 19. Paraplatyarthrus pallidus sp. nov., (Holotype, ♂), A, pleopod 1 endopodite and genital papilla; B, pleopod 1 exopodite; C, pleopod 2 endopodite; D, pleopod 2 exopodite; E, pleopod 3 exopodite; F, pleopod 4 exopodite; G, pleopod 5 exopodite. Scale bars: 0.1 mm.

FIGURE 20. The position of posterolateral corner (PLC) of epimera 1 to 7 in dorsal view; Type A, PLC in pereonal epimera 1 – 3 rounded, in 4 – 7 posteriorly directed; Type B, PLC in pereonal epimera 1 – 4 rounded, in 5 – 7 posteriorly directed.