An integrated study of Atopobathynella (Parabathynellidae, Bathynellacea) species reveals restricted distributions in a complex hydrogeological setting: two new species from the Pilbara (Australia) Author Perina, Giulia Author Camacho, Ana I. Author White, Nicole E. Author Callan, Shae K. Author Abello, Jenny S. Author Morgan, Liesel Author Guzik, Michelle T. text Contributions to Zoology 2024 2024-05-10 93 4 324 370 https://doi.org/10.1163/18759866-bja10063 journal article 10.1163/18759866-BJA10063 1875-9866 14680568 Atopobathynella pagetae sp. nov . (figs. 10-12) LSID: urn:lsid:zoobank.org:act: 15850A3D- DC5D-4117-B327-66DE6667169A Type locality : Bore RC 18 KOOD1710 ( 22° 35’ 4.83“S , 119° 10’ 54.339”E ), Gudai Darri , Pilbara , Western Australia . Material examined : Holotype : WAM C76667 male, on permanent slide, bore RC18 KOOD1710 ( 22° 35’ 4.83“S , 119° 10’ 54.339”E ), Gudai Darri, Pilbara , Western Australia . Lythe M , Paget S. 11 March 2021 ( stygo net haul). Paratypes : WAM C76656 female , WAM C 76657 male , WAM C76658 female , WAM C 76659 female , WAM C76660 male , WAM C76661 male , WAM C76662 male , WAM C 76666 female, all on permanent slide, bore RC18 KOOD1702 ( 22° 35’ 13.0452“S , 119° 10’ 35.2842”E ), Gudai Darri , Pilbara , Western Australia . Lythe M , Paget S. 11 March 2021 ( stygo net haul) . WAM C76668 female on permanent slide , WAM C76669 male on permanent slide, bore RC18 KOOD1702 ( 22° 35’ 13.0452”S , 119° 10’ 35.2842”E ), Gudai Darri , Pilbara , Western Australia . Lythe M , Paget S. 5 November 2021 ( stygo net haul) . Additional material : WAM C76672 1 female in ethanol 100 %, WAM C76673 9 specimens in ethanol 100 %, WAM C76674 1 specimen in ethanol 100%, bore RC18 KOOD1702 ( 22° 35’ 13.0452“S , 119° 10’ 35.2842”E ), Gudai Darri , Pilbara , Western Australia . Curran, M. , Paget S. 5November2021 ( stygo net haul) ; WAM C 76675 48 specimens in ethanol 100% bore RC18 KOOD1702 ( 22° 35’ 13.0452”S , 119° 10’ 35.2842”E ), Gudai Darri , Pilbara , Western Australia . Lythe M , Paget S. 11 March 2021 ( stygo net haul) . WAM C76676 1 male 4 females , bore RC18 KOOD1710 ( 22° 35’ 4.83”S , 119° 10’ 54.339”E ), Gudai Darri , Pilbara , Western Australia . Lythe M , Paget S. 11 March 2021 ( stygo net haul) . Description male holotype ( WAMC 76667): Body length of 0.98 mm . Body six times as long as maximum width, elongated, almost cylindrical, segments progressively widening and lengthening towards posterior end of body (fig. 10). Antennula (fig. 11A): six-segmented. First two articles thicker and longer than the rest, fourth and sixth article similar in length, shorter than fifth which is similar in length to the third article. Antennal organ not protruded, represented by one long and strong seta at inner distal corner of second article. Inner flagellum small and square. Article five with three terminal aesthetascs, one very long, and sixth article with three unequal terminal aesthetascs. Antennula setation as in fig. 11A. Antenna (fig. 11C): one-segmented; with four terminal setae, three smooth and one plumose. Labrum (fig. 11D): flat, free edge with 16 main teeth, seven on each side and two centrals. Paragnaths : absent. Mandible (fig. 11E): pars incisiva with four teeth; pars molaris with five strong and denticulate claws, with the most distal one modified (slightly longer and thicker), and the two most proximal ones joined together; tooth of ventral edge absent. Mandibular palp with one long distal seta not exceeding the pars molaris. Maxillula (fig. 11F): proximal endite with four unequal claws; distal endite with five claws, all denticulated, and three smooth subterminal setae on the outer distal margin, with one shorter than the others. Maxilla (fig. 11G): four-segmented, setal formula 2, 4, 15, 1. Thoracopods I to VII (fig. 12A–G): length gradually increasing from ThI to IV, last four thoracopods similar in size. Epipod absent on ThI. Small epipod present in all the rest of the thoracopods, about half of the length of the corresponding basipod. All basipods with one smooth, distolateral seta similar or slightly shorter than first article of the endopod. Exopod one-segmented in all thoracopods; exopod of ThI shorter than the corresponding first two articles of the endopod, exopod similar in length to the first two articles of the endopod in ThII to VII; with three barbed setae, two terminal ones, with the inner seta longer than the outer one, and one subterminal longer than the outer terminal seta. Endopod four-segmented, first article short with one smooth seta on ThI and without seta on the rest of thoracopods, second and third articles long and similar in length; second article with one plumose external seta in all thoracopods; third article with one internal seta on ThI and one small external distal seta on article three of the other thoracopods; fourth article very reduced with two strong claws of different length in ThI to III and only one long strong claw in ThIV to VII. Setal formula of endopods: ThI1 + 0/1 + 1/1 + 0/2 ThII to III0 + 0/0 + 1/0 + 1/2 ThIV to VII0 + 0/0 + 1/0 + 1/1 Thoracopod VIII (figs. 11H, I): compact, balloon shape. Penial region with massive protopod without frontal protrusion, outer lobe narrow, almost triangular, not defined at base in latero-external view; dentate lobe similar to outer lobe and with four/five small teeth; inner lobe as outer lobe. Basipod elongated over-reaching the outer and inner lobe, with small distal crest or protuberance and one seta of uncertain interpretation on the inner side. Pleopod I (fig. 12H): one long plumose seta on each side. Uropod (fig. 12I): sympod about seven times the length of the endopod and almost five times as long as wide, with seven subequal spines and one distal spine slightly longer and thicker than the others. Endopod shorter than exopod, with row of setules, a long dagger-shaped structure drawn out distally with terminal setules, and two barbed setae similar in length on the distolateral angle twice as long as the dagger-shaped structure. Exopod with two very long barbed terminal setae similar in length and one short and basal seta. Pleotelson (fig. 12J): with two small smooth lateral setae (one on each side); anal operculum not pronounced. Furca (fig. 12J): each ramus almost square, with four different barbed spines, the two distal ones slightly longer. Two dorsal plumose setae, the internal one short, one quarter of the length of the other one, and the outer one is one and a half times the length of the long- est furcal spine. FIGURE 10 Atopobathynella pagetae sp. nov. habitus (male holotype WAMC76667). Female paratypes differs from males in the second antennular article (fig. 11B) that has no antennal organ but one short seta, and ThVIII (fig. 11J) which is small and round with a curved spine. Variability: Variability was observed in body size, (males 0.95–1.2 mm , and females 1.06– 1.19 mm , number of teeth on labrum (16 to 18), teeth on pars incisiva of mandible (three or four), number of setae on the third segment of maxilla (14 or 15),number of setae on the last article of ThIII (one or two), number of setae on exopod of uropod (three or four), number of spines on sympod (six to eight), number of spines on furca (three to five). Etymology: The name of the species is dedicated to Siobhan Paget, one of the collectors of the species.