Ozestheria rufa ( Dakin, 1914 )

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 : 131-135

Ozestheria rufa ( Dakin, 1914)

Fig. 42

Cyzicus (Estheria) rufa Dakin, 1914: 295 , 301–302, fig. 2.

Cyzicus (Estheria) rufa – Richter & Timms 2005: 347 .

Ozestheria rufa – Rogers 2020: 24 (species inquirenda).

Diagnosis

Ozestheria rufa is characterized by a short condyle and a wide occipital notch; a nearly straight ventral carapace margin; carapace ornamentation dorsally on carapace with well-developed medium polygonal reticulations, from about mid-carapace ornamentation comprising highly anastomosing nodulous or intermittent lirae (granular appearance); male rostrum with antero-dorsal wing-like flange and protruding, drawn-out apex; female rostrum anterior margin dorsally convex then straight, apex pointed or slightly rounded (not drawn out), ventral margin straight; 16–19 antenna I lobes reaching to antenna II flagellomeres VIII–X; 14–15 antenna II flagellomeres (all males); 23–24 complete thorax segments; 6–20 very small and often widely spaced, conical spines, posterior spines thinner and aciculate.

Differential diagnosis

Ozestheria rufa can be easily differentiated from most other species by the shape and ornamentation of the carapace as well as the male rostrum. The morphologically most similar species are O. lutraria , O. paralutraria sp. nov., O. sarsii and O. christiani sp. nov. It differs from these four species by its carapace ornamentation, which features finer reticulations and intermittent, nodulous, anastomosing lirae from about mid-carapace instead of reticulations. The apex of the female rostrum of O. lutraria and O. paralutraria is drawn out into an elongate tip. No other species of Ozestheria features the wing-like flange antero-dorsally on the male rostrum.

Type material

Syntypes AUSTRALIA – Western Australia • 2 ♀♀; Lakeside, Boulder City ; 9 Aug. 1913; W.B. Alexander leg.; WAM 7730 .

Other material examined

AUSTRALIA – Western Australia • 3 ♂♂; Lake Carnegie, Toonil Pool ; 26°10′27.3″ S, 122°56′16.9″ E, 8 Jun. 2020; D.J. Cale leg.; WAM C78011 , C80198 , C80199 • 1 ♂; Lake Carnegie, Toonil Pool ; 26°10′27.3″ S, 122°56′16.9″ E, 8 Jun. 2020; D.J. Cale leg.; NHMW-ZOO-CR-28494 .

Type locality

Western Australia, Lakeside, Boulder City.

Description

Males

CARAPACE ( Fig. 42a ). Length 10.6–11.3 mm (HT: 10.6 mm), height 5.9–6.2 (HT: 5.9 mm). Coloration reddish-orange, crowded growth bands lighter. 35–46 (HT: 46) growth lines 18–24 (HT: 24) widely spaced and 16–23 (HT: 22) crowded.

CARAPACE SHAPE. Dorsal margin straight, distinct dorso-posterior corner. Posterior margin broadly rounded, suboval, equicurvate (b/H 0.45–0.49, HT: 0.46). Mid-section of ventral margin nearly straight, second growth phase widely rounded. Umbo position submedian (Cr/L 0.29–0.30, HT: 0.30).

CARAPACE ORNAMENTATION ( Fig. 42f–i ). Larval valve smooth (probably due to abrasion). In dorsal part of carapace, growth bands with strongly reticulating, net-like lirae. In following growth bands and the remainder of non-crowded growth bands, lirae less strongly reticulating, but still anastomosing; lirae intermittent (particularly dorsally within growth bands). Crowded growth bands too narrow to show ornamentation (granular, nodular under SEM). Concentric ridges slightly raised, broad, with moniliform nodules on the dorsal margin. Setae short and thin, rarely preserved (setal pores in one row along all growth lines under SEM).

HEAD ( Fig. 42j ). Condyle short, rounded; occipital notch wide. Condyle lacking anterobasal hump. Margin between condyle and ocular tubercle straight. Ocular tubercle weakly to well developed, forming obtuse angle (~110°) with rostrum. Anterior margin of rostrum strongly convex, antero-dorsally with small, wing-like flange. Apex protruding, pointed, weakly rounded, nearly rectangular. Ventral margin of rostrum weakly concave to straight, with small anterior notch. Naupliar eye small, roundish. Antenna I long with 16–19 lobes (HT: 19), reaching to antenna II flagellomeres VIII–X (HT: IX). Antenna II with 14–15 flagellomeres (HT: 14).

THORAX. 25–26 (HT: 26) segments, 23–24 (HT: 24) thoracopod-bearing and two posterior limbless segments not reaching dorsal margin. Only mid-body thoracopod-bearing segments with short spines or setae on dorsal extensions; posterior segments without dorsal spines or setae.

THORACOPOD III (only WAM C78011; Fig. 42n ). 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. 42l ). 6–20 spines (HT: 20). First (anterior) spine enlarged. Spines very small, conical, variable in size and spacing. Posterior-most spine aciculate. Dorsal margin straight to weakly concave. Right terminal claw more strongly curved than left.

FURCA ( Fig. 42l ). Proximally with dorsomedial longitudinal row of 6–15 (HT: 11) setae, row ending distally in a single conical spine. Distal part ⅓–½ of furcal length, with numerous small denticles.

Females (syntypes)

CARAPACE ( Fig. 42b–c ). Length 8.4–8.7 mm, height 4.5–4.6 mm. Coloration dark brown, nearly black. 18–19, of these 16 widely spaced and 2–3 crowded.

CARAPACE SHAPE. Dorsal margin straight, dorso-posterior corner distinct. Posterior margin oval, greatly extending posteriorly, supracurvate (0.39–0.42). Ventral margin nearly straight. Umbo well developed, extending above dorsal margin, position submedian (0.28–0.29).

CARAPACE ORNAMENTATION. Larval valve and several following growth bands with irregular, nodulous, medium reticulation (mainly comprising pentagons, hexagons or heptagons). From about mid-carapace ornamentation transitioning to highly anastomosing nodulous lirae; lirae appear intermittent, resulting in granular appearance. Lirae become more pronounced ventrally and posteriorly on carapace. Concentric ridges well developed, raised and broad. No setae visible.

HEAD ( Fig. 42k ). Condyle rounded, short, only weakly protruding; occipital notch wide. Condyle lacking anterobasal hump. Margin between condyle and ocular tubercle straight. Ocular tubercle weakly (?) developed, forming obtuse (~–120°) angle with rostrum. Anterior margin of rostrum dorsally convex, otherwise straight. Apex pointed or slightly rounded (not drawn out), with acute angle (~70°). Ventral margin of rostrum straight.

THORAX. Last few segments without dorsal extensions or spines.

TELSON ( Fig. 42m ). 6–9 spines. First (anterior) spine enlarged. All spines rather small. Anterior spines, conical, subequally and widely spaced; posterior spines slightly thinner, more drawn out and aciculate. Dorsal margin straight, last ~¼ concave. Left and right terminal claws equally curved.

FURCA ( Fig. 42m ). Distal part ⅓–½ of furcal length, with numerous small denticles (number of setae cannot be determined as individuals were dried out).

Distribution ( Fig. 42o )

Ozestheria rufa is known from central and southern Western Australia.

Remarks

The two female syntypes are in rather poor condition and appear to have dried out at some point in the past. For this reason, many taxonomically relevant characteristics (e.g., number of body or antennal segments, head shape) could not be assessed. Furthermore, both individuals have been removed from their carapaces, but the bodies and carapace halves were stored together, making it impossible to assign the respective carapace to each body. The latter is not very problematic as they are of similar size and morphologically highly similar. The carapace ornamentation could not be studied in detail due to firmly attached dirt, which could not be removed by strong and continuous sonification.

The original description of O. rufa by Dakin (1914) was brief and poorly illustrated. The carapace appeared much narrower and thus more oval. The head lacked the occipital notch (giving it a widely rounded appearance) and the rostrum was probably shown from antero-lateral, giving it a more pointed impression. Because all syntypes are female, their morphological features were described in detail and not abbreviated as for the females of other species.

We first hesitated to assign the genetically studied males (provisionally termed O. sp. X10) to O. rufa . In the geometric morphometric analyses of carapace shape ( Fig. 5 ), O. rufa comb. nov. appears distinct from all other species and does not overlap with O. sp. X10 when individuals are plotted on the PC1– PC2 plane; however, they fully overlap on the PC2–PC3 plane (Supp. file 1_2.2). Ozestheria rufa was classified as O. sp. X10 (probability 100%), but the associated typicality score (0.04) was low. The apparent differences could also be an artifact of the overall low number of specimens in conjunction with sexual dimorphism. As the historic syntypes are both poorly preserved females and the freshly collected material all males, a direct comparison of soft body features (e.g., rostrum shape) was not possible. The caparace ornamentation, however, is highly similar. Together with the overall similarity in carapace shape, we decided that the more conservative approach to treat these as a single species is preferrable. More detailed future studies with more specimens and a better representation of males and females might clarify their species status.

Figures

Fig. 42. Ozestheria rufa (Dakin, 1914). a. Carapace, male (WAM C78011).b. Carapace, female, syntype (WAM 7730). c. Carapace, dorsal view (left valve only) female syntype (WAM 7730). d–e. Carapace ornamentation (female, syntype, WAM 7730; positions marked in b by rectangles). d. Dorsal carapace. e. Mid-carapace.f. Carapace male (paratype WAM C780119), SEM. g–i. Carapace ornamentation (male, WAM C78011; positions marked in f by rectangles), SEM. g. Mid-dorsal carapace. h. Mid-carapace. i. Ventral carapace. j–k. Head (antennae not shown). j. Male (WAM C78011). k. Female, syntype (WAM 7730). l–m. Telson. l. Male (WAM C78011). m. Female, syntype (WAM 7730). n. Male, third left thoracopod (WAM C78011). o. Distribution map (produced in ArcMap 10.7; see caption Fig. 7 for sources). Scale bars: a–c, f= 1 mm; d–e, g–i=0.1 mm; j–n = 0.5 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.