Ozestheria pellucida ( Timms, 2018 )

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 : 108-110

Ozestheria pellucida ( Timms, 2018)

Fig. 34

Ozestheria pellucida Timms, 2018: 8–10 , fig. 5.

Ozestheria pellucida – Rogers 2020: 24.

Diagnosis

Ozestheria pellucida is characterized by a short condyle and a wide occipital notch; a rounded ventral carapace margin; carapace whitish, translucent; carapace ornamentation nodular or granular with punctae to small reticulations dorsally within growth bands; male rostrum with convex anterior margin, apex strongly rounded with right angle, ventral margin convex; 10 (male) antenna I lobes reaching to antenna II flagellomere VII; 10 (male) antenna II flagellomeres; 21 complete thorax segments; 14 spines, spines on anterior half short and conical, posteriorly aciculate and increasing in size; 14 furcal setae.

Differential diagnosis

Ozestheria pellucida can be easily distinguished from other Australian species of Ozestheria with a short condyle by its carapace ornamentation and possibly carapace size and coloration as well as the shape of the male rostrum. The granular or nodular carapace ornamentation is unique for species with a short condyle, remotely similar only to O. richteri sp. nov. and O. rufa . However, O. rufa differs in the shape of their rostrum (more pointed and less rounded than of O. pellucida ) and has larger carapace sizes (> 8 mm vs ~ 5 mm). In O. richteri the granular ornamentation is present only in later growth bands; it further has a clear hump at the base of the condyle (absent in O. pellucida ), fewer (19 vs 21) complete thorax segments and a darker colored carapace. Ozestheria pellucida and O. richteri are the species with the shortest carapaces compared to other species with short condyles, though young individuals of other species will have similar sizes, of course. Similarly, the whitish translucent or pellucid carapace is characteristic for O. pellucida but also some individuals or populations of other species can have similar carapace colorations.

Type material

Holotype (not examined)

AUSTRALIA – Western Australia • 1 ♂; Kimberley, Gardner Plateau , rock pool; 14°47′28.8″ S, 126°30′32.1″ E; Mar. 2012; A. Cross leg.; WAM C72091 .

Paratype (not examined)

AUSTRALIA – Western Australia • 1 ♂; same data as for holotype; WAM C72092 ).

Paratype

AUSTRALIA – Western Australia • 1 ♂; same data as for holotype; WAM C72092 .

Type locality

Western Australia, Kimberley, Gardner Plateau, rock pool, 14°47′28.8″ S, 126°30′32.1E.

Description

Male

CARAPACE ( Fig. 34a–c). Length 5.0 mm, height 2.8 mm. Coloration whitish-translucent. 14 growth lines, 13 widely spaced and 1 crowded.

CARAPACE SHAPE. Dorsal margin straight, distinct dorsoposterior corner. Posterior margin broadly rounded, suboval, equicurvate (b/H 0.54). Ventral margin widely rounded. Umbo position submedian (Cr/CL 0.28).

CARAPACE ORNAMENTATION ( Fig. 34d–i). Ornamentation on all growth bands of granular appearance. Larval valve and following growth bands punctate to finely reticulated (‘small reticulation’, best seen under SEM); further ventrally on carapace, ornamentation nodular or granular with punctae dorsally on growth bands. No lirae visible. Concentric ridges shallow and punctate. Setae spiniform, preferentially preserved on the midposterior and posteroventral part of carapace (setal pores in single line along all growth lines under SEM).

HEAD ( Fig. 34j). Condyle short, rounded, only weakly protruding; occipital notch wide. Condyle lacking anterobasal hump. Margin between condyle and ocular tubercle straight concave. Ocular tubercle well developed, forming obtuse, nearly rectangular angle (~100–120°) with rostrum. Anterior margin of rostrum widely convexly curved. Apex strongly rounded with nearly rectangular angle. Ventral margin of rostrum with notch anteriorly, then convex. Naupliar eye elongated, triangular. Antenna I long with 10 lobes, reaching to antenna II flagellomere VII. Antenna II with 10 flagellomeres.

THORAX. 22 segments, 21 thoracopod-bearing and one posterior limbless segment not reaching dorsal margin.

TELSON ( Fig. 34k). 14 spines. First (anterior) spine enlarged. Spines on anterior half of telson short, thin, conical, subequal in length; following spines increasing in size and more widely spaced, posterior-most spines elongate, aciculate. Dorsal margin anteriorly slightly convex, mid-section straight. Right terminal claw more strongly curved than left.

FURCA ( Fig. 34k). Proximally with dorsomedial longitudinal row of 14 setae, row ending distally in a single conical spine. Distal part ⅓ of furcal length, with numerous small denticles.

Distribution ( Fig. 34l)

The species is known only from its type locality in northern Western Australia.

Remarks

So far, only males of O. pellucida are known and no genetic data is available.The most notable differences compared to the original description by Timms (2018) is the larger number of thoracic segments (22 vs 18) and furcal setae (14 vs 10) observed in the studied paratype. The latter is notable as Timms (2018) used this characteristic to distinguish O. pellucida from O. packardi , which according to Timms usually has more than 20 furcal setae. However, none of the various O. packardi -like species described herein (all species with a long condyle and a narrow occipital notch) has such a high number of furcal setae. Timms (2018) compared O. pellucida only against O. packardi and O. mariae in the diagnosis, the only two Australian species which formerly had been assigned to Caenestheriella due to their long condyle and a narrow occipital notch. However, O. pellucida clearly has a short condyle and wide occipital notch, features that were shared with all other Australian species of Ozestheria except O. packardi and O. mariae known at that time.

The carapace shape of O. pellucida is distinct from that of all other species (overall very low typicality scores) and is most similar to that of O. fuersichi sp. nov. ( Fig. 5). Although O. pellucida was classified as O. sp. X10 (probability 92.6%, which probably represents O. rufa ), this classification was not supported by the very low typicality score (0.00).