Ozestheria gemina, Schwentner & Hethke, 2025

Schwentner, Martin & Hethke, Manja, 2025, Revision of the Australian Ozestheria Schwentner & Richter, 2015 (Crustacea: Branchiopoda: Spinicaudata) fauna, with the descriptions of 27 new species, European Journal of Taxonomy 992, pp. 1-172 : 60-65

Ozestheria gemina sp. nov.

urn:lsid:zoobank.org:act:13753FE1-0128-4CB7-A344-E4F776360B0A

Fig. 20

Ozestheria sp. N 1 – Schwentner et al. 2015a: figs 2, 6.

Ozestheria cf. berneyi (N) – Schwentner et al. 2020: figs 1–2.

Ozestheria sp. N – Hethke et al. 2023: fig. 11.

Diagnosis

Ozestheria gemina sp. nov. is characterized by a medium long condyle and rather narrow occipital notch; a rounded ventral carapace margin; carapace ornamentation with polygonal reticulations on larval valve and early growth bands, following growth bands with anastomosing lirae, which become more pronounced and regular in later growth bands, where lirae terminate before the concentric ridge, punctae between lirae; male rostrum anterior margin straight to weakly convex, apex pointed with acute angle (~45–60°, rarely close to 90°), ventral margin deeply concave with obtuse angle about half-length; female rostrum anterior margin straight to slightly convex (sometimes undulating), apex pointed (~45– 60°) and drawn out into acute tip, ventral margin weakly concave; 12–22 (males) or 13–18 (female) antenna I lobes reaching to antenna II flagellomeres VI–X (male) or III–VIII (female); 11–15 (male) or 11–15 (female) antenna II flagellomeres; 23–25 complete thorax segments; 14–24 telsonic spines, spines mostly small, conical and subequal in size and spacing, 2–3 (up to 5) larger spines interspersed; 5–15 furcal setae.

Differential diagnosis

Ozestheria gemina sp. nov. can be easily distinguished from most other Australian species of Ozestheria by the combination of its carapace shape and ornamentation (combination of reticulations and lirae), the pointed male rostrum apex and the telsonic spination (many small spines with 2–5 larger spines interspersed). Morphologically most similar are O. fuersichi sp. nov. and O. berneyi . Ozestheria berneyi has a shorter condyle and the carapace ornamentation has polygonal reticulations dorsally within growth bands. Ozestheria fuersichi is smaller (carapace length 3.7–5.1 mm), has a nearly straight ventral carapace margin, carapace ornamentation with more widely spaced, nodular lirae, and the female rostrum has a concave anterior margin.

Etymology

The species name derives from the Latin word ‘ geminus ’ (‘the twin’), referring to its similarity to its sister species O. berneyi .

Type material

Holotype

AUSTRALIA – Queensland • ♂; Yapunyah pool 36 km N of highway; 27°49′09.6″ S, 144°09′26.5″ E; 28 Feb. 2011; M. Schwentner and B.V. Timms leg.; GenBank no: KJ705433 ( COI); AM P.91204.

Paratypes

AUSTRALIA – Queensland • 1 ♂, 1 ♀; same data as for holotype; GenBank nos: KJ705435, KJ705436 ( COI); AM P.91206 to P.91207 • 1 ♂; same data as for holotype; GenBank no: KJ705435 ( COI); NHMW- ZOO-CR-28475 .

Other material examined

AUSTRALIA – Queensland • 1 ♂; Yarromere Station, Morra Creek (M1); 21°28′51.9″ S, 145°49′34.0″ E; 3 Apr. 2009; M. Schwentner and B.V. Timms leg.; AM P.91250 • 1 ♂; roadside claypan; 29°31′42.5″ S, 146°12′20.5″ E; 21 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91232 • 1 ♂, 1 ♀; grassy turbid swamp; 27°41′52.4″ S, 146°45′44.7″ E; 18 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91257, P.91258 • 2 ♂♂, 2 ♀♀; Cyclestheria grassy swamp; 27°40′48.8″ S, 146°38′02.7″ E; 18 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91225, P.91226, P.91251, P.91252 • 1 ♂, 2 ♀♀; dugout 21 km E of Thargomindah ; 28°02′05.2″ S, 144°03′15.7″ E; 27 Feb. 2011; M. Schwentner and B.V. Timms leg.; AM P.91208 to P.91210 . – New South Wales • 1 ♂, 1 ♀; Bloodwood Station, Upper Crescent Pool ; 29°32′33.6″ S, 144°52′16.5″ E; 30 Mar. 2009; M. Schwentner and B.V. Timms leg.; AM P.91188, P.91189 • 2 ♂♂, 1 ♀; Bloodwood Station, Lower Crescent Pool ; 29°32′34.5″ S, 144°51′31.6″ E; 19 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91233 to P.91235 • 2 ♀♀; Gidgee Lake ; 29°33′10.4″ S, 144°50′12.7″ E; 19 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91227, P.91228 • 3 ♂♂, 1 ♀; cane grass swamp SE of Woolshed ; 29°31′35.3″ S, 144°51′39.2″ E; 21 Feb. 2011; M. Schwentner, S. Richter and B.V. Timms leg.; AM P.91221 to P.91224 • 2 ♀♀; Bloodwood Station, Vosper Pool ; 29°32′03.9″ S, 144°50′37.7″ E; 19 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91246, P.91247 • 1 ♂, 1 ♀; Muella Station, Muella Vegetated Pool 3; 29°30′12.0″ S, 144°55′37.4″ E; 31 Mar. 2009; M. Schwentner and B.V. Timms leg.; AM P.91190, P.91191 • 1 ♀; Muella Station, Muella Vegetated Pool 4; 29°30′00.7″ S, 144°54′59.6″ E; 31 Mar. 2009; M. Schwentner and B.V. Timms leg.; AM P.91186 • 2 ♂♂, 2 ♀♀; Muella Station, Upper Lake Eliza ; 29°25′46.0″ S, 145°04′12.6″ E; 31 Mar. 2009; M. Schwentner and B.V. Timms leg.; AM P.91187, P.91229 to P.91231 • 2 ♂♂; Muella Station, Lismore Bore ; 29°31′50.7″ S, 144°59′28.1″ E; 19 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91239, P.91240 • 1 ♂; Yungerina black box swamp; 29°26′09.1″ S, 145°04′40.3″ E; 20 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.82534 • 4 ♀♀; Yantabulla black box swamp; 29°20′17.8″ S, 145°00′09.7″ E; 20 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91242 to P.91245 • 1 ♂; Mitchell Highway 152 km from Bourke ; 31°11′45.0″ S, 146°51′31.4″ E; 18 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.81401 • 1 ♂; Mitchell Highway , 40 km N of Nyugen; 31°11′45,9″ S, 146°51′30,1″ E; 1999; S. Richter and B.V. Timms leg.; AM P.91208 • 1 ♂; claypan-like W of Engonia ; 29°18′32.8″ S, 145°44′06.9″ E; 21 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91241 • 1 ♂, 1 ♀; pool S of Gerara ; 29°13′51.4″ S, 146°18′22.6″ E; 21 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.82577, P.82578 • 1 ♂, 1 ♀; excavated area W of Yarrabundai ; 33°07′28.5″ S, 147°32′09.8″ E; 23 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91236, P.91237 • 2 ♂♂, 3 ♀♀; thoura poplar box swamp; 29°16′11.2″ S, 144°40′25.3″ E; 24 Feb. 2011; M. Schwentner, S. Richter and B.V. Timms leg.; AM P.91211 to P.91215 .

Additional material (not examined)

AUSTRALIA – New South Wales • 5 juvs; Muella Station, Lower Lake Eliza ; 29°25′28.9″ S, 145°03′41.8″ E; 22 Feb. 2011; M. Schwentner, S. Richter and B.V. Timms leg.; AM P.91216 to P.91220 • 1 juv.; Muella Station, Carrols Bore ; 29°29′08.7″ S, 144°59′13.0″ E; 31 Mar. 2009; M. Schwentner and B.V. Timms leg.; AM P.P.80859 • 1 ♀; Yantabulla black box swamp; 29°20′17.8″ S, 145°00′09.7″ E; 20 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91203 • 1 ♂; Bloodwood Station, Lower Crescent Pool ; 29°32′34.5″ S, 144°51′31.6″ E; 19 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91248 • 1 ♀; Bloodwood Station, Gidgee Lake ; 29°33′10.4″ S, 144°50′12.7″ E; 19 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91196 • 2 ♀♀; Bloodwood Station, Freshwater Lake ; 29°29′14.7″ S, 144°49′59.0″ E; 19 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91201, P.91202 • 2 juvs; Bloodwood Station , western fence N of Titanic; 29°24′58.4″ S, 144°46′52.8″ E; Mar. 2006; B.V. Timms leg.; AM P.91183, P.91184 • 1 ♂, 2 ♀♀, 1 juv.; Tiltargara ; 31°51′09.9″ S, 144° 52′22.4″ E; 22 Jan. 2010; M. Schwentner and B.V. Timms leg.; raised from sediment; AM P.91238, P.91197 to P.91199 . – Queensland • 1 juv.; Rockwell Station, Busters black box swamp, Blue Lakes ; 28°47′53.9″ S, 145°00′58.5″ E; 31 Mar. 2009; M. Schwentner and B.V. Timms leg.; AM P.91185 • 1 juv.; Yarromere Station, Morra Creek (M1); 21°28′51.9″ S, 145°49′34.0″ E; 3Apr. 2009; M. Schwentner and B.V. Timms leg.; AM P.91192 • 1 ♀; Cyclestheria grassy swamp; 27°40′48.8″ S, 146°38′02.7″ E; 18 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91195 .

Type locality

Australia, Queensland, Yapunyah pool 36 km N of Highway, 27°49′09.6″ S, 144°09′26.5″ E.

Description

Males

CARAPACE ( Fig. 20a, c–d). Length 4.6–7.5 mm (HT: 4.6 mm, mean: 6.1 mm), height 2.6–4.7 mm (HT: 2.6 mm, mean: 3.8 mm). Coloration varying from yellowish to yellow-orange, red-orange and light brown; outer margin lighter. 15–52 (HT: 22, mean: 25) growth lines, 15–24 (HT: 17, mean: 18) widely spaced and 0–34 (HT: 5, mean: 7) crowded.

CARAPACE SHAPE. Dorsal margin straight, distinct or rounded dorso-posterior corner. Posterior margin broadly rounded, suboval (more circular than in many other species), supra- to equicurvate (b/H 0.43– 0.48; HT: 0.48, mean: 0.46). Ventral margin broadly rounded. Umbo position anterior (Cr/L 0.20–0.25; HT: 0.20, mean: 0.21).

CARAPACE ORNAMENTATION ( Fig. 20e–g, i). Larval valve and first few growth bands with shallow, inconspicuous reticulations (poorly visible in many specimens, may appear granular) forming mainly irregular pentagons or hexagons. Reticulations gradually replaced by lirae in first few growth bands. Lirae subparallel, strongly anastomosing or branching, becoming more pronounced and regular on growth bands of later ontogenetic stages, where they terminate before the concentric ridge (only seen in SEM). Lirae can be inconspicuous, especially on lighter colored carapaces. Under SEM, fine punctae visible between lirae in early ontogenetic stages, which are irregular to absent in later ontogenetic stages. Crowded growth bands with pronounced, parallel lirae, anteriorly nodular and intermittent (visible predominately under SEM). Concentric ridges raised; under SEM smooth in early ontogenetic stages and with nodules at the upper margin in moniliform row in later ontogenetic stages. Spiniform as well as filiform setae present (mainly preserved on outer concentric ridges), usually ~5 spiniform setae between two filiform ones; setal pores in single row along all growth lines.

HEAD ( Fig. 20j). Condyle medium long, distally rounded; occipital notch spacing intermediate between narrow and wide. Condyle lacking anterobasal hump. Margin between condyle and ocular tubercle straight to strongly concave (HT: weakly concave). Ocular tubercle weakly developed, forming obtuse angle (ranging from nearly straight to nearly rectangular; HT: nearly rectangular;) with rostrum. Anterior margin of rostrum straight to weakly convex. Apex pointed, acute (~45–60°; rarely close to 90°), but not drawn out. Ventral margin of rostrum deeply concave with obtuse angle about half-length, pointing apex slightly downwards. Naupliar eye elongated, shaped suboval to sub-triangular. Antenna I long with 12–22 lobes (HT: 17, mean: 18), reaching to antenna II flagellomeres VI–X (HT: VIII, mean: VIII). Antenna II with 11–15 flagellomeres (HT: 10, mean: 12).

THORAX. 23–25 (HT: 25, mean: 24) segments, 23–25 (HT: 24, mean: 24) thoracopod-bearing and none to two (HT: one) posterior limbless segment not reaching dorsal margin. Last ~16 thoracopod-bearing segments with spine or setae bearing dorsal extensions. Dorsal extensions increasing in size posteriorly over successive segments (until ~10 th last segment). Armature starts with small setae, which increase in size and number over following ~6 segments, following segments with fewer setae and central large spines. Posterior segments with few stout spines.

THORACOPOD III (only P.91205; Fig. 20n). Endite I short and curved dorsally. Endites II–V broad, decreasing in size. Endite V palp two-segmented, basal segment shorter than endopod. Exopod ventral extension subequal in extension to endopod, dorsal extension wide, narrowing distally, overreaching epipod. Epipod long, cylindric.

TELSON ( Fig. 20l–m). 15–21 spines (HT: 17, mean: 19). First (anterior) spine enlarged. Following spines mostly tiny, conical, usually 2–3 (rarely up to five; HT: 2) larger spines interspersed (of these usually one of intermediate size) in anterior ⅔ of telson length. Sometimes an additional enlarged, aciculate spine posteriorly. Spines equally spaced. Dorsal margin usually straight, sometimes posterior ¼ curved. Right terminal claw more strongly curved at tip than left terminal claw in most individuals, sometimes both equally curved.

FURCA ( Fig. 20l–m). Proximally with dorsomedial longitudinal row of 5–15 (HT: 11, mean: 11) setae, row ending distally in a single conical spine. Distal part ~⅔ of furcal length, with numerous small denticles.

Females

Overall appearance as in males. Carapace ( Fig. 20b) length 4.5–7.8 mm (mean: 6.8 mm), height 2.7– 4.8 mm (mean: 4.2 mm); 17–31 (mean: 23) growth lines, of these 14–24 (mean: 18) widely spaced and 0–13 (mean: 4) crowded. Anterior margin of rostrum straight to slightly convex, sometimes undulating ( Fig. 20k). Apex pointed (~45–60°), drawn out into acute tip; ventral margin only weakly concave, overall rostrum shape trapezoidal. Antenna I with 13–18 (mean: 16) small lobes, lobes smaller than in males; reaching to antenna II flagellomeres III–VIII (mean: VI). Antenna II with 11–15 flagellomeres (mean: 13). 23–25 (mean: 24) segments, of these 23–25 (mean: 24) thoracopod-bearing and none to one posterior limb-less segment not reaching dorsal margin. Telson with 14–24 (mean: 19) dorsal spines; left and right terminal claws usually equally curved, sometimes right more strongly curved. Furca with 5–13 setae (mean: 9).

Distribution ( Fig. 20o)

Common and widely distributed in the arid regions of central and northern New South Wales and southern Queensland (e.g., catchments of Murray-Darling Basin, Bulloo River), rarely northern Queensland (northern Cooper Creek catchment). This species lives in a wide variety of habitats, ranging from clear freshwater lakes to vegetated swamps, poplar box swamps, turbid claypans and cane grass swamps, and hyposaline lakes.

Remarks

Schwentner et al. (2015a) suggested that either O. sp. M or N might represent O. berneyi . By studying the type material, we were able to identify O. sp. M as O. berneyi (for details see remarks of O. berneyi ). The authors furthermore suggested that O. sp. N comprises two closely related species (O. sp. N1 and N2). Only two specimens of O. sp. N2 were available (which might not be fully grown), which does not allow proper assessment of the species morphological variability and putative differentiation from O. sp. N1. Therefore, we decided not to formally describe O. sp. N 2 in this publication and also did not include them in the formal description of O. gemina sp. nov.

Because of its intermediate-sized condyle, O. gemina sp. nov. was included in the geometric morphometric analyses of the short-condyle as well as of the long-condyle species ( Figs 5–6). In both analyses, O. gemina was largely distinct and overlapped partly with O. berneyi , O. rubra , O. henryae sp. nov. and O. richteri sp. nov. ( O. richteri was fully included in O. gemina ) of the short-condyled species and partly with O. timmsi sp. nov., O. setifera sp. nov., O. sivesae sp. nov., O. mariae , O. marthae sp. nov., O. cancellata comb. nov., O. weeksi sp. nov., and O. pilbarensis sp. nov. of the long-condyled species. In the analysis of long-condyled species, O. gemina forms the extreme shape at positive scores along PC1.

It is notable that presumably older males (those with more crowded growth bands) tend to have a more strongly rounded rostrum apex.