Pseudolimnocythere sofiae, 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 sofiae sp. nov.

Figs 3C, D , 4 , 5

Type locality.

Poiano springs, Upper Secchia Valley, municipality of Villa Minozzo, province of Reggio nell’Emilia, Emilia-Romagna region, coordinates 44°23'31"N, 10°26'20"E, 423 m a.s.l. (Suppl. material 1: Figs S1, S4B). Average discharge> 400 l s-1, water temperature between 8.9 and 10.8 °C, conductivity ranging from ~9 to ~17 mS cm-1 ( Stoch et al. 2009a). Poiano is the major spring complex of a large outcrop of Upper Triassic evaporites, comprising a sequence of gypsum-anhydrite and dolostone beds with local salt bodies (Suppl. material 1: Fig. S3). The spring drains an aquifer of unique properties composed of anhydrite with halite lenses at depth and gypsum at the surface (both with high NaCl content) ( Chiesi et al. 2010). Sample collected by Fabio Stoch on December 21, 2015.

Material investigated.

More than 30 specimens from the type locality and sample of the holotype, and additional specimens from nearby localities (see below). Previously reported as Pseudolimnocythere sp. in Stoch et al. (2009a, b) and P. sp. 1 in Pieri et al. (2015).

Holotype.

GR804, adult ♂, soft parts dissected in glycerine in a sealed slide, valves used for SEM imaging and stored dry in a micropalaentological slide.

Derivation of name.

This species is dedicated to GR’s daughter, Sofia Rossetti Tekleab. Furthermore, among the different meanings of the ancient Greek noun ”σοφία” there are also “knowledge” and “wisdom”. Our hope is that the description of this new species will shed more light on morphological characteristics and evolutionary relationships of the genus Pseudolimnocythere .

Description.

Valves (Figs 3C, D , 4 ). Carapace small, in dorsal view elliptical, valves sub-rectangular in lateral view. Viewed laterally the dorsal edge is sloping gently posteriorly turning into a curve. Anterior end of the carapace broad and rounded. Maximum length at mid height, maximum height in the anterior third. Surface ornamented with subrounded pits, with dimensions increasing towards posterior. In dorsal view, anterior end beak shaped. In internal view: vestibulum well developed, selvage strong and narrow, line of concrescence well developed. Dorsal margin straight, ventral margin concave in the middle part, with an additional closing mechanism where the RV overlaps the LV. Hinge amphidont: LV with smooth cardinal bar swelling anteriorly into a bi or trilobate tooth, posteriorly with a lower small tooth and an upper large socket with several lobes, RV with complementary intercardinal groove, swelling anteriorly into two-three sockets, posterior element with a multilobate tooth. Muscle scars typical of the family: four adductor muscle scars in a vertical row. Sexual dimorphism not very pronounced, with males slightly larger and stouter than females. Average carapace length 0.32 mm.

Appendages (Fig. 5 ). Antennula slender, six-segmented. Second podomere with short setulae on the second half of the anterior margin and a ventro-apical seta reaching c. 1/3 of the length of next segment; third podomere short, with a dorso-apical seta slightly shorter than next segment; penultimate segment consisting of fourth and fifth podomeres fused, with two subequal setae, one posterior and one anterior, at junction of the two fused segments, and distally one posterior seta and three anterior setae, the longer ones reaching beyond tip of next segment; terminal podomere long and thin, distally with a free seta and aesthetasc ya fused at the base with a seta. Antenna with stout, trapezoidal basipodite. Spinneret seta (exopodite) reaching tip of distal claws of endopodite, proximally bowed and nearly straight in the middle part, distal end folded and thin. Endopodite four-segmented; first segment of endopodite with a ventro-apical setae slightly exceeding mid-length of next segment; penultimate segment formed by second and third podomeres fused, with two setae of different length at c. 1/3 of anterior margin, aesthetasc Y and two shorter setae at about half length of posterior margin, and one ventro-apical seta; last segment with two claws, the longest one proximo-posterior and the other distal. Thoracopods (walking legs) four-segmented, with first podomere stout and remaining ones long and slender with straight margins. First segment of first thoracopod with four anterior setae, one proximal, two median and one distal, and a proximo-posterior seta reaching the end of the segment; second podomere with a dorso-apical seta; third and fourth segment without setae; last segment with a distal claw weakly subvided in two parts, the distal one c. 2/3 of the length and narrower. Same setal formula in second and third thoracopod: first segment with three anterior setae and a longer posterior seta; second segment with dorso-apical seta; third segment with no setae; last segment with long claws. Hemipenis with chitinized anterior lobe having a narrow base and distally wider and sub-quadrate.

Measurements.

Valve length 303-331 µm (n = 9).

Distribution.

In addition to individuals drifted from the Poiano spring, rare specimens of Pseudolimnocythere sofiae sp. nov. were found in some nearby habitats reported by Stoch et al. (2009b): in the interstitial of Secchia river (where spring waters come out), Sologno stream and Lucola stream; in the gypsum caves named Risorgente di Ca’ della Ghiaia (cadastral number 244 ER) and Tanone Grande della Gaggiolina (cadastral number 154 ER); no specimens were found in all other types of groundwater and interstitial habitats examined in the same area, or in springs located in soils on marly-arenaceous deposits upstream of the evaporite outcrops ( Stoch et al. 2007, 2009b).

Differential diagnosis.

Pseudolimnocythere sofiae sp. nov. is easily distinguishable from described congeneric species. The better described species is P. hartmanni Danielopol (1979) from which it differs in overall outline, size, ornamentation and development of the ventral posterior margin. Pseudolimnocythere sp. ( Peterson et al., 2013, fig. 8U) seems much larger, although measurements were taken from the figure (where a LV is erroneously reported as a RV). Pseudolimnocythere hypogaea (sensu Karanovic and Pesce 2001, figs 1-6) is slightly smaller, stouter in the overall appearance and with a characteristic wavy dorsal margin. Pseudolimnocythere sp. ( Danielopol 1980, fig. 11A-F) from the Skulijca cave displays a faint ornamentation and a stout anterior marginal rim; the overall external shape is not visible in the photos provided but in internal view the central curve of the ventral margin is less pronounced.

Pseudolimnocythere sp. ( Peterson et al. 2013) is stouter, with a different surface ornamentation and an oblique dorsal margin. Pseudolimnocythere sp. sensu ( Schornikov et al., 2014) is slightly smaller (302-311 µm), with a surface ornamentation occurring only in the marginal areas. The specimen illustrated in Schornikov et al. (fig. 4k, 2014) is probably a juvenile. The drawings of P. hypogaea by Klie (1938) and Karanovic and Pesce (2001) clearly display a sinuous dorsal margin and the lack of the additional closing mechanism in the ventral area. The morphology of the hemipenis differs markedly from that of the extant species of Pseudolimnocythere for which males have been described (Fig. 6 ).

Note.

The distal segment of walking legs in Pseudolimnocythere abdita sp. nov. and P. sofiae sp. nov. is fused with the basal part of the claws (Figs 2C-E , 5C-E ). The same pattern is reported for the Limnocytheridae as well (see Meisch 2000).

Figures

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.

Figure 4. Pseudolimnocythere sofiae sp. nov. A, B VP 1125, adult ♂ C-H GR 797, adult ♀ I VP 1120, adult (sex undetermined) J VP 1122, adult (sex undetermined) K VP 1121, adult (sex undetermined) A left valve, internal view B right valve, internal view C left valve, internal view D right valve, internal view E left valve, internal view, detail postero-ventral corner F left valve, internal view, detail antero-dorsal corner G right valve, internal view, detail antero-dorsal corner H right valve, internal view, detail postero-ventral corner I carapace, dorsal view J carapace, ventral view K carapace, left lateral view. Scale bar: 100 μm (A-D, I-K); 66 μm (E-H).

Figure 5. Pseudolimnocythere sofiae sp. nov., GR 804, adult ♂ A antennula B antenna C first thoracopod D second thoracopod E third thoracopod D hemipenis. Scale bar: 50 μm (A, E); 64 μm (F).

Figure 6. Hemipenis of Recent species of Pseudolimnocythere A P. hypogaea (redrawn from Klie, 1938) B P. hypogaea (redrawn from Karanovic and Pesce 2001) C P. hartmanni (redrawn from Danielopol 1979). Not to scale.