Pseudolimnocythere abdita, Rossetti & Stoch & Mazzini, 2022

Rossetti, Giampaolo, Stoch, Fabio & Mazzini, Ilaria, 2022, A reassessment of the origin and distribution of the subterranean genus Pseudolimnocythere Klie, 1938 (Ostracoda, Loxoconchidae), with description of two new species from Italy, Subterranean Biology 43, pp. 33-60 : 33

Pseudolimnocythere abdita sp. nov.

Figs 1 , 2 , 3A, B

Type locality.

Rheocrene spring Cirone, road from Bosco di Corniglio to Cirone pass, municipality of Corniglio, province of Parma, Emilia-Romagna region, coordinates 44°26'59"N, 10°00'38"E, 1126 m a.s.l. (Suppl. material 1: Figs S1, S4A). Natural free-flowing spring located on shales and limestone (Suppl. material 1: Fig. S2), estimated average discharge 2 l s-1, water temperature 7.9-8.5 °C, electric conductivity c. 360 μS cm-1, pH 7.5-7.7 ( Bottazzi et al. 2011). Sample collected by Elisa Bottazzi on May 15, 2007.

Material investigated.

One adult female designated as holotype, with valves stored dry in a micropaleontological slide (used for SEM) and soft parts dissected in glycerine and kept in a sealed slide (VP1152). Previously reported as Pseudolimnocythere cf. hypogea Klie , 1938 in Bottazzi et al. (2008, 2011) and P. sp. 1 in Pieri et al. (2015). Material deposited in the Ostracod Collection of the Department of Chemistry , Life Sciences and Environmental Sustainability, University of Parma .

Derivation of name.

From the Latin adjective abditus-a-um, meaning hidden, concealed, but also mysterious, due to the fact that only one individual of this species was collected despite repeated samplings in the type locality and in other springs of the same region.

Description.

Valves (Figs 1 , 3A, B ). Subrectangular in lateral view. Anterior margin broadly rounded, posterior margin rounded and blunty pointed. Surface ornate with fossae. Hinge reduced invicidont: LV with smooth bar, smooth anterior tooth and tripartite posterior socket; RV with smooth groove and anterior socket, posterior tooth consisting of a large element and two smaller teeth towards the anterior part. Muscle scars not visible.

Appendages (Fig. 2 ). Antennula six-segmented. Second podomere with setulae on anterior margin and a ventro-apical seta slightly longer than the next segment; third podomere short, bearing a dorso-apical seta about two times its length; fourth segment formed by fourth and fifth podomeres partially fused, with one posterior and one anterior subequal setae inserted near fusion line, and distally one posterior seta and three anterior setae reaching or slightly beyond tip of next segment; terminal podomere long and thin, distally with a seta fused at the base with aesthetasc ya, and a free seta of the same length as the latter. Antenna with robust basipodite. Spinneret seta (exopodite) gently arched proximally, central part nearly straight, distal end decidedly bent and with pointed tip almost reaching distal end of terminal claws. Endopodite four-segmented. First podomere with a ventro-apical setae reaching slightly beyond mid-length of next segment. Penultimate segment consisting of second and third segments fully fused, with two short setae inserted halfway the length of anterior margin, and two unequal setae and aesthetasc Y at c. 4/7 of posterior margin, tip of the latter slightly surpassing segment distal end, and one robust ventro-apical seta; last segment with two claws, one longer inserted more proximally and the other apically. Thoracopods (walking legs) four-segmented, first podomere sturdier and more enlarged than following ones. First segment of first thoracopod with four setae in anterior position, one proximally, one medially and two distally, and a posterior seta inserted proximally; second podomere with a dorso-apical seta shorter than next segment; third and fourth segment without setae; last podomere distally bearing a robust claw with proximal third enlarged. Second and third thoracopod with analogous setal arrangement; first segment with three anterior setae and a longer posterior seta; second segment with a dorso-apical seta, third segment without setae; terminal claw of second thoracopod more enlarged and stouter than in other thoracopods, that of third thoracopod consisting of three parts with gradually decreasing diameter. Male unknown.

Measurements.

Valve length 308 μm, height 173 μm (n = 1).

Distribution.

The species is known from its type locality only.

Differential diagnosis.

Pseudolimnocythere abdita sp. nov. differs from other described living or subfossil species of the genus with “sloping” valves (see below) in its intermediate size, being larger than P. sp. sensu Schornikov, 2013 (c. 0.25 mm) and P. sp. Montanari et al. 2021 (c. 0.28 mm), and shorter than P. sp. Peterson et al. 2013 (c. 0.35 mm), and P. sp. Danielopol 1980 (0.34-0.36 mm). For all these species, only the morphology of the valves is known, therefore a comparison with the soft parts of P. abdita sp. nov. is not possible.

Remarks.

Pseudolimnocythere abdita sp. nov. is here formally described, in spite of the fact that a single female specimen was available. We have decided to do this for the following reasons:

both valve and soft features are described, allowing us to clearly distinguish the new species from its congenerics;

so far only two other living species are known for the genus Pseudolimnocythere , which is of particular importance to better understand the origin, phylogenetic affinities and distribution of non-marine representatives of the family Loxoconchidae;

the habitat from which the species was collected strikingly differs from those of other living congeners (see below);

further samplings performed in the type locality and surrounding spring areas did not yield additional specimens.

We are thus confident that Pseudolimnocythere abdita sp. nov. can be unambiguously identified on the characters presented here.

Figures

Figure 1. Pseudolimnocythere abdita sp. nov., VP 1152, adult ♀ A left valve, internal view B right valve, internal view. Scale bar: 100 μm.

Figure 2. Pseudolimnocythere abdita sp. nov., VP 1152, adult ♀ A antennula B antenna C first thoracopod D second thoracopod E third thoracopod. Scale bar: 50 μm.

Figure 3. A, B Pseudolimnocythere abdita sp. nov., VP 1152, adult ♀ C, D Pseudolimnocythere sofiae sp. nov., VP 1125, adult ♂ A right valve, internal view, detail dorsal margin B left valve, internal view, detail dorsal margin D right valve, internal view, detail dorsal margin E left valve, internal view, detail dorsal margin. Scale bar: 40 μm.