Schellencandona capderreyae, Issartel & Marmonier, 2025

Issartel, Colin & Marmonier, Pierre, 2025, Description of five new species of Schellencandona Meisch, 1996 (Ostracoda: Candoninae) from the southern French Alps, a highly diversified area for groundwater ostracods, European Journal of Taxonomy 1022, pp. 85-133 : 96-102

Schellencandona capderreyae sp. nov.

urn:lsid:zoobank.org:act:

Figs 5–7 , 18 , 20 ; Tables 1 , 3

Diagnosis

Small trapezoid candonine of the genus Schellencandona with a carapace length of about 600 µm covered by fossae. LV overlaps the RV. Greatest H of LV located at 40 and 63% of the animal length (H/L=0.50). Anterior and posterior calcified inner lamella sub-equal amounting to c. 10% of L. A1 without seta on the 3 rd podomere. Male A2: EII and EIII separated with t2 and t 3 male bristles, 3 z setae (z2 transformed in a claw), the longest claw (G2) represents 180% the length of EI. Female A2: EII+III with 3 t and 2 z setae. 2 nd podomere of the mandibular palp bears 3+2 setae. Endopodites of the maxilla (L5) developed in males into prehensile palps slightly curved and asymmetrical. Walking leg (L6) with two g setae. Cleaning leg (L7) 4-segmented, EII and EIII fused, with 2 setae (d1 and dp) on the protopodite. Zenker’s organ with 6 internal rings of spines. The outer lobe a of the hemipenis large and rounded, dorso-distally oriented, the inner lobe b sub-rectangular shaped with anterior and posterior angles rounded. Bursa copulatrix rounded with a well-sclerotized distal strip and an internal conical structure. Female genital lobe widely rounded without any posterior expansion. Ocular structures not visible.

Etymology

The new species is named after Cécile Capderrey who collected this species during her PhD.

Type material

Holotype

FRANCE • ♂, dissected appendages mounted in glycerine, valves stored in ethanol; Alpes de Haute Provence district, Noyer-sur-Jabron municipality; 44.1668° N, 5.9251° E; 468 m a.s.l.; Jun.–Jul. 2010; C. Capderrey leg.; interstitial habitat of the Jabron River before its confluence with the Buech River ; MNHN-IU-2023-705 .

Allotype

FRANCE • ♀; same data as for holotype; MNHN-IU-2023-706 .

Paratypes

FRANCE • 1 ♂; same data as for holotype; MNHN-IU-2023-707 • 2 ♂♂; same locality as for holotype; undissected; UCBLZ 2012-3-208 • 2 juvs; same data as for holotype; UCBLZ 2012-3-153-3 to UCBLZ 2012-3-153-4 .

Other material examined

FRANCE • 8 juvs, undissected; UCBLZ.2012-3-208.

Description

MEASUREMENTS. Holotype, ♂ (MNHN-2023-705): LV: L = 600 µm, H = 300 µm (H/L = 0.50). RV = 585 µm, H = 285 µm (H/L = 0.48). W = 205 µm (W/L = 0.34). Range for males (n = 2): L = 595–600 µm, H = 300 µm, W=195–205 µm. Allotype, ♀ (MNHN-2023-706): LV: L=537 µm, H=260 µm (H/L=0.48). RV: L=530 µm, H=232 µm (H/L=0.43). W=180 µm (W/L=0.33).

CARAPACE. Whitish with ornamentation consisting of fossae on its entire surface. General shape of carapace trapezoid ( Figs 5 , 18C–D ). LV overlaping RV with marked cardinal angles. Highest H located at 40 and 63% of animal length. H/L = 0.50 for male and H/L=0.48 for female. Carapace slightly compressed centrally in dorsal view ( Fig. 5C, G ), with greatest W at ⅓ and ⅔ L, representing 33% of L. Anterior and posterior ends weakly beak-shaped.

VALVES. For both valves ( Fig. 5 ), anterior margin widely rounded, while posterior margin more pointed, dorso-posterior margin straight and dorso-anterior margin slightly concave. RV smaller than LV (3% of L difference). LV with ventral margin slightly concave in male and straight in female ( Fig. 5D, H ). RV with a dorsal margin slightly concave ( Fig. 5B, F ), while LV is straight ( Fig. 5D ) or poorly curved ( Fig. 5H ). Dorsal margin representing 33% of L in both male and female. Anterior and posterior calcified inner lamellas sub-equal, representing 10% of L. Fused marginal valve zone narrow, representing 2.5% of L for both male and female, with straight and dense radial pore canals, more numerous anteriorly.

ANTENNULE, A1 ( Figs 6A , 7A ). I+II: A-1l(pu), P-2l(pu) / III: 0/ IV: A-1s/ V: A-1l, P- 1m /VI: A-1l/VII: A-2l-1s(α), P-1l/ VIII: D-2l-ya-1l(cs). Using IV podomere as reference, the ratios of podomeres are 1.4- 1-1.3-1-1.6-1.6 from III to VIII. The ya aesthetasc very long, 7–11 × as long as IV podomere.

ANTENNA, A2 ( Figs 6B–D , 7B–D ). Protopodite: coxa with 3 setae, 2 long and smooth, 1 short and plumose; basis with 1 long posterior seta; exopodite with 1 long and 2 short setae; EI with 1 posterior aesthetasc Y (equalling to 60% of the length of EI) and distally 2 setae (1s and 1m).

MALE A2 ( Fig. 6B–D ). EII and EIII segmented as 2 individuated podomeres. EII with 1 short aesthetasc (y1) and 4 t setae, t1 medium, t4 short, t2 and t3 transformed in male bristles with length equal to 80% of EI length. EIII with 1 short aesthetasc (y2), 3 external z setae, z1 and z3 equal or slightly longer than EIV length, z2 transformed in long claw (160% of EI length). G1 reduced (56% of EI length), G2 well-developed (180% of EI length), G3 reduced to long bristle (84% of EI length). EIV with 2 claws, posteriorly 1 long (Gm, 170% of EI length) and anteriorly 1 reduced (GM, 52% of EI length), 1 aesthetasc (y3, 60% of EI length) associated with subequal seta, g seta present.

FEMALE A2 ( Fig. 7B–D ). EII and EIII fused, with anteriorly 2 short aesthetacs (y1 and y2), 3 t setae, distally 2 z setae (z1 twice the length of EIV and z2 short). G2 claw reduced (55% of EI length). G1 and G3 claws well-developed and sub-equal (170% EI length). EIV with anteriorly 1 long (GM, 140% of EI length) and posteriorly 1 reduced claw (Gm, 66% of EI length), 1 aesthetasc (y3, 45% of EI length) with subequal seta, g seta present.

MANDIBLE. Consists of coxal plate and 4-segmented palp (Mdp). Coxa typically shaped, heavily chitinized with masticatory part. 1 st podomere of Mdp ( Figs 6F , 7F ) with externally exopodite plate and 2 long setae, internally with 2 long setae (1 plumose S1) and 2 short setae (1 smooth, α, 1 plumose, S2). 2 nd podomere with externally 2 setae and internally group of 3 smooth setae and second group of 2 setae (1 long and 1 short, β). 3 rd podomere with externally 3 setae, distally 1 long and smooth seta (γ) and internally 3 small setae. 4 th podomere with 2 serrated and long claws (190% of 3 rd podomere length) and 3 small setae.

MAXILLULAR PALP (Mx1palp, Figs 6E , 7E ). Two-segmented: 1 st segment with 4 apical plumose setae on outer corner. 2 nd segment with 2 claw-like setae (4 time as long as 2 nd segment) and 4 thinner setae. MAXILLA (L5, Figs 6I–J , 7H ). With protopodite bearing 1 anterior seta (a) and 2 exterior setae (b and d), masticatory process (endite) apically with group of 11 setae. Exopodite plate with 2 filaments. Male endopodites transformed in asymmetrical clasping organs (right one more developed, left one slender), slightly curved with 2 short but thick setae on ventral side and thin apical seta. In female, similar set of setae observed on protopodite and 2 filaments on exopodite. Endopodite with 3 short apical setae.

WALKING LEG (L6, Figs 6G , 7G ). Five-segmented. Protopodite and EI without seta. EII with f seta and EIII with 2 g setae. EIV with 2 short setae (h1 and h3) and long claw (h2) equalling 160% of EI length.

CLEANING LEG (L7, Figs 6M , 7J ). Four-segmented (with EII and EIII fused). Protopodite with 1 short (d1) and 1 long setae (dp, 130% of EI length). EI without seta, EII+EIII with short seta (g). EIV with 3 long setae: h1 (sub-equal to EI length), h2 and h3 (130% and 200% of EI length, respectively).

CAUDAL RAMUS (CR, Figs 6L , 7I ). Robust with medium-sized sp seta (22%–27% of anterior margin of CR, just reaching basis of Gp), short sa seta and 2 long and curved claws (Ga and Gp representing around 80–84% to 64–67% of anterior margin of CR, respectively), both claws serrated.

FEMALE GENITAL LOBE ( Fig. 7I ). Widely rounded without posterior expansion. Oocyte large (12% of valve length).

MALE GENITAL ORGANS. Zenker’s organ ( Fig. 6K ) with 6 internal rings of spines representing 20% of total length of carapace. Hemipenis ( Fig. 6H ) with distal outer lobe (a) large and rounded, dorso-distally oriented, inner lobe (b) sub-rectangular shaped with anterior and posterior angles rounded and small plication on ventral side. Lobe h not observed. Labyrinth well-sclerotized and divided in 4 sections, section d4 weakly reticulated. Copulatory tube thin located inside rounded bursa copulatrix (e) with well-sclerotized curved distal strip and internal conical structure. M-process flat with broad rounded dorso-distal part, linked to C strip, and thin basal part reaching d4 section of labyrinth.

OCULAR STRUCTURES. Not visible.

Ecology and distribution

Schellencandona capderreyae sp. nov. was collected from the interstitial habitat of a single river, the Jabron River, a tributary of the Durance River ( Fig. 1 ), in a single sample at an elevation of 468 m a. s.l. It was sampled at the downstream end of a gravel bar (groundwater upwelling zone) at a depth of 90 cm into the riverbed sediment. Water had a temperature of 18.7°C, an electrical conductivity of 382 µS. cm-1, a pH of 7.9 and a rather high dissolved oxygen concentration (i.e., 6.3 mg ·L- 1).

Specialisation to groundwater: its very long aethetascs (ya on A1, Y and y3 on A2), the lack of visible eyes and the large size of the oocyte (12% of the body length) suggest a specialisation of the species to groundwater life. Schellencandona capderreyae sp. nov. can be considered, for the moment, as an endemic stygobiotic species.

Taxonomic remarks

The general shape of the carapace of the new species (trapezoid) is very similar to those of S. schellenbergi and S. simililampadis , but differs by the dorsal margin, which is parallel to the ventral margin in the new species ( Figs 5 , 18C ), while it is inclined backwards in the two other species.

The new species differs from the other European species. It is very close to S. simililampadis and S. schellenbergi , but differs in the three following characteristics: (1) A2 with a z2 seta transformed in a claw in males (see Fig. 19A for A2 of S. simililampadis ); (2) stocky shape of the hemipenis, with the dorso-distal location of the outer a lobe, the small size of the h lobe (not visible) and the curved distal sclerotized strip on the bursa copulatrix. In addition, S chellencandona capderreyae sp. nov. differs from the above-mentioned two species by (1) the A1 with a reduced number of setae, especially the lack of seta on podomere III in both males and females (seta present in S. schellenbergi ), (2) the single anterior seta on podomere IV of A1 (two setae in the two other species), and (3) the lack of d and e setae on L6 (both present in S. simililampadis ).

The relationships between S chellencandona capderreyae sp. nov. and the four other species described in this work are detailed in the Discussion.

Figures

Fig. 5. Schellencandona capderreyae sp. nov. A–D. Holotype, ♂ (MNHN-IU-2023-705) A. Right view of the undissected specimen. B. Right valve, external view. C. Dorsal view of whole carapace. D. Left valve, external view. E–H. Allotype, ♀ (MNHN-IU-2023-706). E. Right view of the undissected specimen. F. Right valve, external view. G. Dorsal view of whole carapace. H. Left valve, external view. Scale bars = 100 µm. Arrows point to anterior margin

Fig. 6. Schellencandona capderreyae sp. nov., holotype, ♂ (MNHN-IU-2023-705). A. Antennule (A1). B. Antenna (A2). C. Detail of antenna, external view. D. Detail of antenna, internal view. E. Maxillula (Mx1) palp. F. Mandibular palp (Mdp). G. Walking leg (L6). H. Hemipenis, outer view. I. Left 5th limb (with clasping organ). J. Right clasping organ. K. Zenker’s organ. L. Caudal ramus. M. Cleaning leg (L7). Abbreviations: see Material and methods. Scale bars = 20 µm.

Fig. 7. Schellencandona capderreyae sp. nov., allotype, ♀ (MNHN-IU-2023-706). A. Antennule (A1). B. Antenna (A2). C. Detail of antenna, internal view. D. Detail of antenna, external view. E. Maxillula (Mx1) palp. F. Mandibular palp (Mdp). G. Walking leg (L6). H. Maxilla (L5). I. Caudal ramus with genital lobe. J. Cleaning leg (L7). Abbreviations: see Material and methods. Scale bars = 20 µm.

Fig. 18. A–B. Schellencandona danielopoli sp. nov., holotype, ♂ (MNHN-IU-2023-701). A. Entire animal, right view. B. Dorsal view. C–D. Schellencandona capderreyae sp. nov., holotype, ♂ (MNHN-IU-2023-705). C. Entire animal, right view. D. Dorsal view. E–F. Schellencandona mercantourensis sp. nov., holotype, ♂ (MNHN-IU-2023-708). E. Entire animal, left view. F. Dorsal view. G–H. Schellencandona claretae sp. nov., holotype, ♀ (MNHN-IU-2023-711). G. Entire animal, right view. H. Dorsal view. I–J. Schellencandona malardi sp. nov. male (MNHN-IU-2023-714). I. Entire animal, right view. J. Dorsal view. Scale bars = 100 µm. Arrows point to anterior margin.

Fig. 20. Hemipenis (top) and L5 clasping organs (bottom) of the five new species of Schellencandona Meisch, 1996. Scale bars = 20 µm.

Fig. 1. Geographic distribution of the species of Schellencandona Meisch, 1996 in the southern French Alps. Solid lines = rivers; X = study sites without Schellencandona; dotted lines = western extension of Alpine glaciers during the Last Glacial Maximum (based on Julian 1997; Bosq et al. 2018).

Fig. 19. A. Schellencandona simililampadis (Danielopol, 1978), detail of male A2, external view (redrawn after Danielopol 1978). B. Schellencandona sp. J1 (UCBLZ 2012-3-14-36), detail of male A2, external view. Abbreviations: see Material and methods. Scale bars = 20 µm.