Ozestheria rubra ( Henry, 1924 )

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 : 126-131

Ozestheria rubra ( Henry, 1924)

Figs 40–41

Estheria rubra Henry, 1924: 121 , 134–135, fig. 32.

Caenestheria rubra – Richter & Timms 2005: 346 .

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

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

Ozestheria rubra – Rogers 2020: 24 .

Diagnosis

Ozestheria rubra is characterized by a short condyle and wide occipital notch; a rounded ventral carapace margin; carapace ornamentation with medium to large, well-developed polygonal reticulations, each polygon with polygonal secondary ornamentation (best seen under SEM); male rostrum with strongly convex anterior margin, apex rounded with right angle, ventral margin concave, pointing apex downwards; female rostrum anterior margin straight or weakly convex, apex pointed (in some individuals elongated, drawn out), ventral margin slightly concave; 13–22 (male) or 13–20 (female) antenna I lobes reaching to antenna II flagellomeres VII–X (male) or III–V (female); 12–15 (male) or 10–18 (female) antenna II flagellomeres; 22–23 complete thorax segments; 14–27 small, unequally sized and spaced conical telsonic spines, spines in the central part of the telson enlarged; 3–15 furcal setae.

Differential diagnosis

See differential diagnosis of O. elliptica .

Type material

Syntype AUSTRALIA – New South Wales • 1 ♀; Goorimpa Station; 1923; Henry (?) leg.; AM P.6773 .

Other material examined

AUSTRALIA – New South Wales • 2 ♂♂, 3 ♀♀; big lake near Cumeroo; 29°15′22.2″ S, 145°15′03.8″ E; 20 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91397 to P.91401 • 1 ♂, 4 ♀♀; 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. 91379, P.91389–91392 • 1 ♂, 1 ♀; Bloodwood Station, Woolshed Saltlake ; 29°31′44.3″ S, 144°51′11.1″ E; 19 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91393, P.91394 • 1 ♂; Bloodwood Station, Woolshed Saltlake ; 29°31′44.3″ S, 144°51′11.1″ E; 19 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; NHMW-ZOO-CR-28489 • 1 ♂; Bloodwood Station, Roszkos Paleolake ; 29°27′42.9″ S, 144°48′12.5″ E; 19 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91380 . – Northern Territory • 1 ♂, 4 ♀♀; island hyposaline lake 60 km N of Kulgera; 25°19′23.2″ S, 133°12′41.7″ E; 10 Mar. 2011; M. Schwentner and B.V. Timms leg.; AM P.91415 to P.91419 • 4 ♂♂, 2 ♀♀; lake 20 km W of Erldunda; 25°14′36.5″ S, 132°59′40.3″ E; 6 Mar. 2011; M. Schwentner and B.V. Timms leg.; AM P.91410 to P.91414 , P.91396 • 1 ♂, 3 ♀♀; creek into Mygoora; 25°22′ S, 132°38′ E; 6 Apr. 2011; Low leg.; P.91383 to P.91386 . – South Australia • 3 ♂♂, 1 ♀; quarry Pool Algebuckina; 27°54′13.9″ S, 135°48′47.1″ E; 12 Mar. 2011; M. Schwentner and B.V. Timms leg.; AM P.91387 , P.91402 to P.91404 .

Additional material (not examined)

AUSTRALIA – New South Wales • 3 juvs; Bloodwood Station , turbid marsilea swamp S of Junction Pool; 29°31′33.3″ S, 144°50′23.6″ E; 23 Feb. 2011; M. Schwentner, S. Richter and B.V. Timms leg.; AM P.91388 , P.91405 , P.91406 .

Type localities

New South Wales, Marra and Budda Stations (Darling River) and Goorimpa Station (Paroo River; 29°34′ S, 144°17′ E).

Description

Males

CARAPACE ( Fig. 40b–c, e–f ). Length 6.7–9.3 mm (mean: 8.0 mm), height 3.3–5.5 mm (mean: 4.7 mm). Coloration brown to whitish (nearly translucent), outer margin lighter, whitish. 18–32 (mean: 23) growth lines, 13–20 (mean: 16) widely spaced and 2–14 (mean: 7) crowded.

CARAPACE SHAPE. Dorsal margin straight, distinct dorso-posterior corner. Posterior margin broadly rounded, suboval, supracurvate (b/H 0.40–0.46; mean: 0.43). Ventral margin widely rounded. Umbo position anterior (Cr/L 0.17–0.22, mean: 0.20).

CARAPACE ORNAMENTATION ( Fig. 40g –h, j ). Larval valve with shallow reticulations. Each growth band with well developed, strongly raised, medium to large reticulations. Reticulations form polygonal mesh across each growth band with each polygon usually being a pentagon, hexagon or heptagon. Polygon-size increasing during ontogeny, largest in the dorsal to median part of each growth band; under SEM secondary mesh or polygonal reticulation within each primary polygon (less strongly developed or absent ventrally within growth bands and ventrally on carapace). Ornamentation uniform across all non-crowded growth bands, crowded growth bands usually a single row of polygonal structures resulting in radial appearance. Concentric ridges raised. Setae variable in size; preferentially preserved on ventral and posterior parts of the carapace. Setal pores in single, irregular row along all growth lines.

HEAD ( Fig. 41a–c ). Condyle rounded, short, only weakly protruding; occipital notch wide. Condyle lacking anterobasal hump. Margin between condyle and ocular tubercle straight or weakly concave. Ocular tubercle weakly to well developed, forming obtuse (~90°–120°) angle with rostrum. Anterior margin of rostrum strongly convex.Apex strongly rounded, nearly rectangular. Ventral margin of rostrum deeply concave with obtuse angle about half-length, pointing apex slightly downwards; small notch anteriorly in most individuals. Naupliar eye small or elongated, sub-triangular or roundish. Antenna I long with 13–22 (mean: 17) lobes, reaching to antenna II flagellomeres VII–X (mean: VIII). Antenna II with 12–15 (mean: 13) flagellomeres.

THORAX. 22–24 (mean: 23) segments, 22–23 (mean: 22) thoracopod-bearing and none to one posterior limbless segment not reaching dorsal margin. Mid to posterior thoracopod-bearing segments with spine bearing dorsal extensions. Dorsal extensions increasing in size posteriorly over successive segments; spines mostly short, in posterior segments with fewer spines and central spines stouter but shorter.

THORACOPOD III (only P.91392; Fig. 40k ). Endite I short and curved dorsally. Endites II–V broad, decreasing in size. Endite V palp one-segmented. Exopod ventral extension subequal in extension to endopod, dorsal extension wide, narrowing distally, overreaching epipod. Epipod long, cylindric.

TELSON ( Fig. 41g –h ). 16–25 (mean: 20) spines. First (anterior) spine enlarged. Spines conical, subequally spaced, anterior spines smaller, followed by several (3–5) larger spines close to the central part of the telson (with few interspersed smaller spines); posteriorly spines slightly thinner and more drawn out and slightly increasing in size (last ⅓ of telson). Dorsal margin either slightly concave or s-shaped (anteriorly slightly convex, posteriorly concavely curved). Right terminal claw more strongly curved than left.

FURCA ( Fig. 41g –h ). Proximally with dorsomedial longitudinal row of 4–15 (mean: 9) setae, row ending distally in a single conical spine. Distal part ½–⅔ of furcal length, with numerous small denticles.

Females

Overall appearance as in males. Carapace ( Fig. 40a, d ) length 5.3–9.0 mm (ST: 7.7 mm; mean: 7.1 mm), height 3.0– 5.6 mm (ST: 4.4 mm; mean: 4.2 mm); 14–30 (ST: 17; mean: 20) growth lines, 13–20 (ST: 14; mean: 15) widely spaced and 0–15 (ST: 3; mean: 5) crowded; Cr/L 0.18–0.22 (ST: 0.20; mean 0.20) and b/H 0.37–0.47 (ST: 0.43; mean: 0.43). Ocular tubercle forming obtuse (~120°–180°) angle with rostrum. Anterior margin of rostrum straight to weakly convex or slightly undulating; apex pointed (not or only weakly rounded), in some individuals tip elongate, drawn out; ventral margin concavely curved (usually less strongly compared to males) or straight ( Fig. 41d–f ). Antenna I with 13–20 (ST: 19; mean: 16) small lobes, lobes smaller than in males; reaching to antenna II flagellomeres III–V (syntype: III; mean: IV). Antenna II with 10–18 (ST: 14; mean: 14) flagellomeres. 22–24 (ST: 22; mean: 23) segments, 22–23 (ST: 22; mean: 23) thoracopod-bearing and none to one posterior limbless segment not reaching dorsal margin. Telson with 14–27 (ST: 19; mean: 18) dorsal spines; left and right terminal claws equally curved. Furca with 3–10 setae (in majority of individuals furca damaged or broken off); distal part ½–¾.

Distribution ( Fig. 41j )

Ozestheria rubra occurs in the central Paroo River and Darling River catchments in northern New South Wales as well central Australia (southern Northern Territory and northern South Australia). Several and maybe even all (not all water bodies have been studied for their water chemistry) habitats are hyposaline.

Remarks

The single type specimen in the collection of the Australian Museum (P.6773) is labeled as a syntype; however, no further type specimens are currently known. In the original description, Henry mentioned three stations from which the species was collected (Marra, Budda and Goorimpa Station). The available syntype is from Goorimpa Station.

The original description by Henry (1924) is based on a few individuals only and does not provide an overview of the intraspecific variability.In the original drawing the carapace is shown with a strong convex curvature along the dorsal margin; this was not observed in the studied syntype or any other individual (the margin was always straight; maybe the carapace was drawn from a slightly ventral perspective); nor does the umbonal region of the drawing match the types or other individuals studied here. Their umbos protrude above the dorsal margin and the larval valves are distinctly smaller than implied by the drawing (in the description, Henry did mention “prominent umbones”). Henry furthermore wrote that the carapace lacked “crowded concentric striae”, which probably are what we refer to as “crowded growth lines”. In fact, these are present in Henry’s type specimens and in many other studied specimens and must have been overlooked by her. In Henry’s drawing the telson is wrongly demarcated from the preceding thorax segments, giving the wrong impression that the telson bears three large spines before the actual spination (these are probably the dorsal extensions of the last thorax segments); also, the spines of the telson are depicted as very long, thin and aciculate. This does not agree with the situation in the syntype or the other studied specimens, where the anterior spines are usually smaller and more conical. Henry noted a “bright red to reddish-brown” color in living specimens. The studied syntype was nearly translucent and devoid of any obvious coloration. Several of the herein studied preserved specimens were also nearly translucent, others were brownish.

In the geometric morphometric analyses ( Fig. 5 ), O. rubra is distinct from most other species and overlaps partly with O. matuwa sp. nov., O. henryae sp. nov., O. richteri sp. nov. and O. gemina sp. nov. in the PCA and LDA. The classification of the O. rubra syntype with O. sp. D1+D2 was strongly supported by a posterior probability of 97.8% and a typicality score of 0.96. The next highest typicality scores were 0.54 and 0.47 for O. matuwa and O. henryae , respectively, but the associated posterior probabilities were low (1.7% and 0.4%).

Schwentner et al. (2015a) delimited two genetic lineages (O. sp. D1 and D2), which are now summarized in O. rubra . The genetic differences between the two were rather low (COI uncorrected p -distances ≤ 4.2%), also compared to the other closely related species O. matuwa sp. nov. and O. henryae sp. nov., which showed distances of 5.4–14.3%. The only apparent morphological difference between O. sp. D1 and D2 are broader concentric ridges on the carapace in O. sp. D1, which does not warrant a separation into two species. Assigning O. sp. D1 and D2 to O. rubra is straightforward due to the morphological congruence and the shared geographic distribution.

Figures

Fig. 40. Ozestheria rubra (Henry, 1924). a–f. Carapace. a. Female, syntype (P.6773). b. Male (P.91392). c. Dorsal view (right valve only, male, P.91392). d. Female (P.91412). e. Male (P.91394), SEM. f. Male (P.91411), SEM. g–j. Carapace ornamentation (positions marked in a, b, e by rectangles, respectively). g. Mid-carapace (male, P.91394), SEM. h. Ventral carapace (male, P.91394), SEM. i. Mid-ventral carapace (female syntype, P.6773). j. Ventral carapace (male, P.91392). k. Male, third right thoracopod (P.91392). Scale bars: b–f=1 mm; g, i= 0.05 mm; j–k= 0.5 mm.

Fig. 41. Ozestheria rubra (Henry, 1924). a–f. Head (antennae not shown). a. Male (P.91394), SEM. b. Male (P.91392). c. Male (P.91410). d. Female, syntype (P.6773; nauplius eye was not visible). e. Female (P.91390). f. Female (P. 91412). g–i. Telson. g. Male (P.91394), SEM. h. Male (P.91392). i. Female, syntype (P.6773; furca broken off).j. Distribution map (circle depicts type localities; produced in ArcMap 10.7; see caption Fig. 7 for sources). Scale bars: a–c, e–f, h =0.5 mm; g=0.2 mm.

Fig. 5. Morphometrics of short-condyled species. Scores on upper PC1 and PC2 of Fourier shape coefficients of 248 outlines, including 233 new individuals and 15 historic type specimens, four of which are drawings ofOzestheria elliptica (Sars, 1897),O. lutraria (Brady, 1886) andO. berneyi (Gurney, 1927). One of the drawings of O. berneyi corresponds to the studied syntype. The names used by Schwentner et al. (2015a) to identify genetically delimited species (e.g., C, D etc.; extended for the newly identified species, e.g., X1) are provided. New specimens are represented by convex hulls, type specimens by data points. lower. Mean shape of each species, calculated based on up to 73 individuals per species.