Atopobathynella beasleyensis 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 : 30-33

Atopobathynella beasleyensis Perina & Camacho , sp. nov.

urn:lsid:zoobank.org:act:04569E4C-E0DE-404C-812A-B2A679851B60

( Figs. 8–9 )

Material examined. Holotype male. AUSTRALIA: Western Australia: Brockman, Pilbara, Karaman GBOT2 KARA08 MCDM, 22°42'59.1726"S, 117°19'34.554"E, 14 September 2022, M. Curran, D. Main ( WAMC 78913 — BES17988 — BMR04610 , permanent slide).

Paratypes: AUSTRALIA: Western Australia: 1 female, WAM C78911 — BES17988 — BMR04608 , permanent slide, same details as holotype . 1 female, WAM C78912 — BES17988 — BMR04609 , permanent slide, same details as holotype . 1 male, WAM C78914 — BES17988 — BMR04611 , permanent slide, same details as holotype . 1 male, WAM C78915 — BES17988 — BMR04612 , permanent slide, same details as holotype .

Additional material: 75 specimens in alcohol ( WAM C78939 — BES17988 ), same details as holotype ; 1 male ( WAM C78940 — BES18677 ), same details as holotype .

Diagnosis. Atopobathynella beasleyensis sp. nov. belongs to a group of Atopobathynella species that have antennal organ (AO) with protuberance and two setae of different length; distal endite of maxillula with five claws; only two setae in the exopod of all thoracopods; homonomous sympod of the uropod; exopod of the uropod with three distal setae and furca with more than five spines. It differs from all other species (except A. chelifera ) by the presence of two setae on exopod of all thoracopods, and by a bilobed outer lobe of male ThVIII. The sequenced specimens differ from all the other Atopobathynella taxa sequenced by COI = 11.1–21.5% and 12S = 33.1–42.3% (Appendices 3, 4).

Description male holotype (WAMC78913). Body length of 0.80 mm. Body almost eight times as long as maximum width, elongated, almost cylindrical, segments slightly widening and lengthening towards posterior end of body.

Antennula ( Fig. 8A ): six-segmented. Articles narrowing from the first to the last one, the second article is the longest, slightly longer than the first, which is longer than the third, the fifth and sixth are equal and shorter than the third, and the fourth is the shortest. Antennal organ represented by two strong, ventral setae of different length and arranged on two protuberances, the longest extends beyond the distal end of fourth article and is over three times longer than the other. Inner flagellum small and almost square with three setae. Articles five and six with three terminal aesthetascs each. Antennular setation as in Fig. 8A .

Antenna ( Fig. 8C ): one-segmented with four smooth setae, three terminal and one subterminal.

Labrum ( Fig. 8D ): almost flat, free edge with 16 teeth, seven on each side and two central ones with the distal end denticulated.

Paragnaths: absent.

Mandible ( Fig. 8E ): pars incisiva with three teeth; pars molaris with four strong claws, the most distal one thicker, denticulated, and almost perpendicular to the others, the two most proximal claws joined together; tooth on ventral edge absent. Mandibular palp with one seta not reaching beyond the pars incisiva.

Maxillula ( Fig. 8G ): proximal endite with four unequal claws; distal endite with five dentated claws; three smooth subterminal setae on the outer distal margin.

Maxilla ( Fig. 8I ): four-segmented, setal formula 2, 3, 11, 1.

Thoracopods I to VII ( Figs. 9A–G ): length slightly increasing from thoracopod one to three, last four similar in size. Small epipod present in ThII to VII, just over half the length of the corresponding basipod. All basipods with one distolateral seta about the length of the first article of the endopod. Exopod one-segmented in all thoracopods; exopod of ThI very short, slightly longer than the first 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 two terminal barbed setae, inner seta long, twice as long as outer one. Endopod four-segmented, first article short with one inner 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 seta on thoracopod I only; third article with one inner seta on ThI , and one small outer distal seta on the rest of thoracopods; fourth article very reduced with two strong claws of different length on ThI , and only one long strong claw on ThII to VII. Setal formula of endopods as follows:

ThI 1+0/1+1/1+0/2

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

Thoracopod VIII ( Figs. 8J, K ): compact, like a balloon slightly elongated. Penial region with massive protopod. Outer lobe rounded with frontal protrusion, shorter than the distal end of basipod, not defined at base in latero-external view and similar to the inner lobe. Dentate lobe with four teeth, two distal and two subdistal. Basipod with one very small frontal crest and two setae of uncertain origin (possibly exopod or endopod).

Pleopod I ( Figs. 9H ): long plumose seta located on the anterior third of the first segment of the pleon in each side.

Uropod ( Fig. 9I ): sympod almost seven and a half times the length of the endopod and almost five times as long as wide, with nine spines, the three distal ones slightly shorter than the six proximal, occupying the distal half of the sympod. Exopod one and a half longer than endopod, with three terminal barbed setae, and one basal seta. Endopod very short distally drawn out into a very long dagger-shaped structure, with setules, distolateral angle bearing two plumose setae, of different lengths (the inner one almost twice as long as outer one), that exceed the tip of the dagger-shaped structure.

Pleotelson ( Fig. 9J ): with one short lateral plumose seta on each side; anal operculum not protruded.

Furca ( Fig. 9J ): rami robust and rectangular, with six barbed spines; two distal spines longer than basal ones that are equal in length. Two dorsal plumose setae, inner seta short, outer seta three times longer than distal spines.

Female paratype differs from male in the second antennular segment ( Fig. 8B ) that bears no antennal organ, but a long smooth seta; five claws on pars molaris of the mandible; thoracopod VIII ( Fig. 8H ) reduced to a small denticle-like appendage.

Variability: variability was observed in body size (males 0.67–0.86 mm and females 0.94–1.14 mm), and number of spines on sympod of uropod (8–11) and furca (5–7).

Distribution and remarks. Atopobathynella beasleyensis sp. nov. has been collected at only one site in the hyporheic habitat of the Beasley Creek, a tributary of the Ashburton River. This species was previously known by Biologic Environmental Surveys as Atopobathynella sp. “Biologic-PBAT050”. Despite being geographically close to A. abelloana sp. nov. and A. rudini sp. nov. (less than 30km), our results indicate it is sister species to A. sp. GrPar, occurring about 60 km southeast ( Figs. 1 , 5 ).

Etymology. The name of the species derives from the Beasley Creek in the Pilbara, where this species was collected.

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 8. Atopobathynella beasleyensis sp. nov. male holotype (WAMC 78913) unless specified. A, AI; B, AI second article (female paratype WAMC 78912); C, AII; D, Lb (male paratype WAMC 78914); E, Md; F, Md (female paratype WAMC 78912); G, MxI; H, pars distalis MxI (female paratype WAMC 78912); I, MxII. J, male ThVIII (latero-external view); K, male ThVIII (latero-internal view); L, female ThVIII (latero-external view) (female paratype WAMC 78912). (O.Lb) outer lobe, (Bsp) basipod, (D. Lb) dentate lobe, (I. Lb) inner lobe). Scale bar: 0.05 mm.

FIGURE 9. Atopobathynella beasleyensis sp. nov. male holotype (WAMC 78913) unless specified. A, ThI; B, ThII; C, ThIII; D, ThIV; E, ThV; F, ThVI; G, ThVII; H, pleopod; I, uropod; J, furcal rami and pleotelson (dorsal view). Scale bar: 0.05 mm.