Atopobathynella runhami Perina & Camacho, 2025

Perina, Giulia, Camacho, Ana I., Morgan, Liesel, Lawrie, Angus, Floeckner, Stephanie & Guzik, Michelle T., 2025, New species of Atopobathynella, Kimberleybathynella and Hexabathynella (Parabathynellidae, Bathynellacea) from the arid zones of Western Australia, Zootaxa 5655 (1), pp. 1-103 : 34-37

Atopobathynella runhami Perina & Camacho , sp. nov.

urn:lsid:zoobank.org:act:7339223F-9CC1-4A81-8977-19ADB9F3B89D

( Figs. 10–11 )

Material examined. Holotype female. AUSTRALIA: Western Australia: Miralga Creek, Sulphur Spring, Pilbara , karaman SSK0021, 21°07'23.0106"S, 119°12'00.0655"E, 15 September 2019, F. Rudin, P. Runham ( WAMC 78880 — BES7664 b, permanent slide). Male unknown.

Additional material: AUSTRALIA: Western Australia: 1 juvenile, Miralga Creek, Sulphur Springs, Pilbara karaman SSK002, 21°07'13.3339"S, 119°11'54.2026"E, 12 July 2019, P. Runham, D. Main ( WAMC 78879 – BES5980 a,in alcohol) ; 1juvenile, Miralga Creek, Sulphur Springs, Pilbara karaman STXKARA01, 21°06'37.7343"S, 119°11'40.1582"E, 17 May 2019, P. Runham, D. Main ( WAMC78883 — BES8285 , in alcohol) ; 3 juveniles in alcohol, karaman STXKARA01, 17 May 2019, P. Runham, D. Main ( WAMC78937 — BES7463 ) .

Diagnosis. Atopobathynella runhami sp. nov. belongs to a group of Atopobathynella species that have distal endite of maxillula with five claws; homonomous sympod of the uropod; exopod of the uropod with two distal setae and furca with few spines. It differs from all other species of Atopobathynella by the female ThVIII “tongue” shaped. The sequenced specimens differ from all the other Atopobathynella species sequenced by COI = 16.1–21.4% and 12S = 28.7–42.3% (Appendices 3, 4).

Description female holotype (WAMC78880). Body length of 1.06 mm. Body about six and a half times as long as maximum width, elongated, almost cylindrical, segments slightly widening and lengthening towards posterior end of body.

Antennula ( Fig. 10A ): six-segmented. First two articles almost square, first three articles with similar length, third article longer than the last three ones, which are equal in length. Inner flagellum small and almost square, with three setae. Articles five and six with three terminal aesthetascs each. Antennular setation as in Fig. 10A .

Antenna ( Fig. 10B ): one-segmented with three setae, two terminal and one subterminal.

Labrum ( Fig. 10C ): almost flat, free edge with 16 teeth, seven on each side, long, and two smaller centrals.

Paragnaths: absent.

Mandible ( Fig. 10D ): pars incisiva with three teeth; pars molaris with five claws, the most distal one thicker, denticulated, and almost perpendicular to the others, the two most proximal ones joined together; tooth on ventral edge absent. Mandibular palp with one long distal seta reaching beyond the pars incisiva.

Maxillula ( Fig. 10E ): proximal endite with four unequal claws; distal endite with five claws, two distal ones smooth, and the other three denticulated, with the basal claw thinner than the others; three smooth subterminal setae on the outer distal margin.

Maxilla ( Fig. 10F ): four-segmented, setal formula 2, 3, 10, 1.

Thoracopods I to VII ( Figs. 11A–G ): length slightly increasing from ThI to III, last four similar in size. Epipod present in ThII to VII, about half of the length of the corresponding basipod ( Fig. 11A ). All basipods with one distolateral seta as long as the first article of the endopod of ThI , and much longer than the first article in other Ths. Exopod one-segmented in all thoracopods; exopod of ThI reaching the middle of the second article of the endopod; exopod of ThII to VII similar in length to the first two articles of the endopod. Exopod of ThI to VII bearing three barbed setae, two terminals, with the outer one very small in ThI , and the inner one long, about five times as long as the outer one in all Ths, one subterminal seta 1.5 times longer than the outer distal one. Endopod four-segmented, first article short with one seta on ThI , and no seta on the rest of thoracopods; second and third articles long and similar in length; second article with one outer plumose seta in all thoracopods and one inner smooth setae only on ThI ; third article with one inner seta on ThI and one small outer seta on the rest of thoracopods; fourth article very reduced with two strong claws of different length and one seta on ThI and only one long strong claw on ThII to VII. Setal formula of endopods as follows:

ThI 1+0/1+1/1+0/3(1)

ThII to VII 0+0/0+1/0+1/1

Thoracopod VIII ( Figs. 10G ): very small, “tongue” shaped.

Pleopod not seen.

Uropod ( Fig. 11H ): sympod about four times as long as wide, two and half times the length of the exopod and about three times the length of the endopod, with seven and five subequal spines, occupying less than the distal half of the sympod. Exopod one third longer than the endopod, with two similar terminal barbed setae, and one basal plumose seta. Endopod distally drawn out into a long dagger-shaped structure, distolateral angle bearing two plumose setae of different lengths, the inner one 1/3 longer than the outer one, and both exceed the tip of the dagger-shaped structure.

Pleotelson ( Fig. 11I ): with one small lateral plumose seta on each side; anal operculum not protruded.

Furca ( Fig. 11I ): rami robust and almost square, with four barbed spines; whose lengths slightly increase from the basal one, which is the shortest, and half of the size of the distal one. Two dorsal plumose setae, the inner one very short and the outer one about two times longer than the distal spines.

Distribution and remarks. Atopobathynella runhami sp. nov. has been collected in the hyporheic habitat at three geographically close sites near Miralga creek, a tributary of the de Grey River Catchment ( Fig 1 ). It was collected in one of the karaman samples with A. jessicae , but our results indicate that A. runhami is genetically distant to A. jessicae and all other Atopobathynella sequenced ( Fig. 5 ).

Etymology. The name of the species is dedicated to Phil Runham, a colleague and one of the collectors of the species.

Figures

FIGURE 1. Atopobathynella species distribution in the Pilbara (WA).

FIGURE 5. ML tree built using the three-genes alignment (COI-12S-18S). Some nodes collapsed for clarity. Supported nodes in green. New species described in red, new putative species in green. *: hyporheic taxa. Blue rectangles: clades supported in the three-genes and two-genes analyses. Orange rectangles: clades supported only in the three-genes analysis.

FIGURE 10. Atopobathynella runhami sp. nov. female holotype (WAMC 78880).A, AI; B,AII; C, Lb; D, Md; E, MxI; F, MxII; G, female ThVIII (latero-external view). Scale bar: 0.05 mm.

FIGURE 11. Atopobathynella runhami sp. nov. female holotype (WAMC 78880). A, ThI; B, ThII; C<ThIII; D, ThIV; E, ThV; F, ThVI; G, ThVII; H, uropod; I, furcal rami and pleotelson (dorsal view). Scale bar: 0.05 mm.