Strandesia mehesi, Kisseih & Higuti & Martens, 2020

Kisseih, Amanor, Higuti, Janet & Martens, Koen, 2020, Re-description of Strandesia sanoamuangae Savatenalinton & Martens, 2010 and description of a new species of Strandesia (Crustacea, Ostracoda) from Grande Terre, New Caledonia, European Journal of Taxonomy 627, pp. 1-28 : 13-20

Strandesia mehesi sp. nov.

urn:lsid:zoobank.org:act:4A4696B2-7442-4F3F-A3A4-CBA9CF203806

Figs 4–7

Differential diagnosis

The present species belongs to the S. vinciguerrae / S. vavrai - group within the genus, which is characterized by a carapace with rounded appearance in lateral view, with the greatest height situated well in front of the middle, a LV overlapping the RV on all sides, and a slight to pronounced skewed asymmetry of the valves in frontal view.

The new species differs from both S. vinciguerrae and S. vavrai in both size and shape of the valves. Strandesia vinciguerrae appears to be its closest relative, but both valves (especially the LV) in the new species are more elongated, the dorsal margins are more equally sloping towards the posterior side and an anterior selvage on the RV appears to be missing in this species. See below for further discussion on the identity of Strandesia vinciguerrae . The valves of Strandesia vavrai ( Müller 1898: plate 16, figs 1–6) are even shorter and the dorsal margins of both valves are almost fully symmetrically rounded. Strandesia kraepelini (G.W. Muller, 1906) , described as Cypris kraepelini from Java ( Müller, 1906), also belongs in this group. This species resembles Strandesia mehesi sp. nov. from New Caledonia, but it is more elongated, with a long straight part of the dorsal margin (rounded in the new species) and also does not show a trace of the anterior selvage in the RV which is present in the specimens from New Caledonia (see redescription in Savatenalinton & Martens, 2010). Several other species resemble S. mehesi sp. nov., but these require further discussion (see below).

Etymology

The present species is named after Gyula Méhes (Budapest, Hungary), a student of E. Daday, who wrote the first comprehensive account of the freshwater ostracods of the New Caledonian archipelago.

Material examined

Holotype

NEW CALEDONIA • ♀; Province Nord, Houailou, Rivière La Túú - Tuu River; 21°15ˊ53˝ S, 165°35ˊ49.8˝ W; 7 m a.s.l.; 14 Nov. 2017; J. Higuti & K. Martens leg.; soft parts dissected in glycerine in a sealed slide, valves stored dry in a micro-palaeontological slide; sample HYNC.1272; MNHN MNHN- HYNC-IU-2014-20304 . Accompanying ostracod fauna: Strandesia sanoamuangae Savatenalinton & Martens, 2010 . Water temperature at time of collecting: 27.1°C; electrical conductivity: 95.6 µS/cm; pH:7.5.

Paratypes

NEW CALEDONIA – Province Nord • 3 ♀♀; same collection data as for holotype; soft parts dissected in glycerine in a sealed slide, valves stored dry in a micro-palaeontological slide; MNHN MNHN- IU-2014-20305 to MNHN-IU-2014-20307 . • 5 ♀♀; same collection data as for holotype; undissected and stored dry in micropalaeontological slides after use for SEM; MNHN MNHN-IU-2014-20308 to MNHN-IU-2014-20312 . • 10 ♀♀; same collection data as for holotype; stored in EtOH; MNHN MNHN-IU-2014-20313 .

Description

Female

CpLL ( Fig. 5A ) sub-ovate and dorsally arched with greatest height situated slightly in front of the middle; anterior and posterior margins rounded, posterior margin slightly narrower; RV slightly overlapping LV dorsally. CpRL ( Fig. 5 B–F) sub-ovate and dorsally arched with greatest height situated slightly anterior of mid length; dorsal arc shallower than in CpLL; LV overlapping RV anteriorly, ventrally and posteriorly; overlap greatest anteriorly and posteriorly. CpD ( Fig. 4E , G–H) and CpV ( Fig. 4F ) subelliptical, with greatest height at ca mid-length, lateral margins sloping to blunt anterior and posterior extremities; LV margin in ventral view sinuous with protrusion at greatest carapace width. CpFr ( Fig. 4I ) slightly skewed, with RV higher than LV. Cp surface in lateral views ( Fig. 5 G–H) with scattered rimmed pores with sensilla and small pits fading toward the centre of the valves; pores, with sensilla not rimmed, denser antero-ventrally.

LVi ( Fig. 4A, C ) with calcified inner lamella wider anteriorly, an internal groove along valve margin. RVi ( Fig. 4B, D ) with calcified inner lamella wider anteriorly, and with anterior selvage marginally inwardly displaced.

A1 ( Fig. 6A ) with seven segments. All segments with apical setae. First segment with 1 short dorsal seta and two long ventro-apical setae. Wouter’s Organ not observed. Second segment trapezoid-like with one short apical seta at dorsal side and one large, ventral Rome Organ (R). Third segment longest of all segments with two short setae; one dorsal and one ventral. Fourth segment with two long dorsal setae and two short dorsal setae; one of short setae approximately half as long as other. Fifth segment with three long dorsal and one short ventral setae. Sixth segment with four long apical setae. Seventh segment with one short aesthetasc seta (Ya), one long seta twice as long as Ya and two long setae.

A2 ( Fig. 6 B–C) biramous with two-segmented protopod, a reduced exopod and three endopodal segments. First protopodal segment with two unequal ventral setae. Second protopodal segment with one long seta. Exopod a small plate with one long seta and two very short but unequal setae. First endopodal segment with one thin ventral aesthetasc, one long apical seta not reaching beyond the last endopodal segment and six natatory setae (five long and one short); the long natatory setae not extending beyond tips of apical claws. Second endopodal segment with two unequal dorsal setae; a group of four ventral setae (“t”-setae; two long and two short); one short seta approximately equalling the length of the terminal segment; three serrated apical claws (G1, G2 and G3) and three apical setae (z1, z2 and z3). Terminal segment with two serrated claws, one long (GM) and one short (Gm); one aesthetasc fused over a short distance with an accompanying seta and one g-seta.

Md Palp ( Fig. 6 D–F) with four segments. First segment with four ventral setae; two long plumose setae, one long smooth seta and one short α-seta; this segment also with a small respiratory plate (not shown). Second segment with four ventral setae (one slender hirsute β-seta about ½ the length of α-seta, three long hirsute setae and one short smooth seta) and three dorsal subapical setae (one long, one about ¾ the length of first and the shortest about ¼ of first). Third segment with six apical setae (one long γ-seta hirsute at the distal half of its length, four smooth setae and one short setae about ⅔ the length of the terminal segment) and four unequal dorsal subapical setae. Fourth segment ( Fig. 6F ) with three claws and three setae apically, claws longer than setae.

Md coxa ( Fig. 6G ) elongated and robust with an apical row of highly sclerotized teeth, largest at the dorsal edge with a general decrease in size toward the ventral edge. Teeth interspersed with setae with two notably strong setae covered with small setules ventral to the two largest teeth respectively and two short unequal hirsute setae ventral to the last tooth. Dorso-distal side of coxa with one short but stout seta.

Mx1 ( Fig. 7A ) (chaetotaxy incompletely illustrated) with a protopod, a two-segmented palp (endopod), three masticatory lobes (endites) and a large branchial plate (the latter not illustrated). Proximal segment of palp with six antero-distal setae (most ventral one longest reaching beyond the longest seta on second segment of palp) and one medial slender seta. Second segment elongated (length twice as width) with three distal claws and three distal setae. Third endite with two large and strongly serrated distal bristles and a proximal seta reaching higher than half the length of the bristles. First endite with two sidewaysdirected bristles (one approximately half the length of the other) and two slender proximal setae not reaching distal edge of the endite.

T1 protopodite ( Fig. 7B ) with b seta, d seta not observed. Protopodite with 14 mostly serrated setae; ten apical and four subapical. Palp (endopodite – not illustrated) elongated, with three unequal apical setae.

T2 ( Fig. 7C ) a walking leg with five segments. First segment with hirsute seta (d1). Second segment with hirsute seta (d2); d2 being ca ¾ the length of d1. Third segment with one subapical hirsute seta e. Fourth segment with two sub-segments (4a and 4b respectively); segment 4a with one long apical hirsute seta (f) and segment 4b with one seta (g), shorter than seta f but reaching beyond the end of the terminal segment. Fifth segment with one apical claw (h2) and one short ventral seta (h1) and one short dorsal seta (h3).

T3 ( Fig 7 D–E) a cleaning limb with three segments. First segment (protopod) with 3 long setae (d1, d2 ventrally and dp dorsally); d1 and d2 with approximately equal length; dp longer than d1 and d2 and reaching higher than distal edge of first endopodal segment. First endopodal segment with ventrosubapical seta e. Terminal endopodal segment with seta f and distal edge as pincer; seta e reaching to half the length of seta f and seta f reaching higher than distal edge of terminal segment. Distal edge of terminal segment with one comb-like seta (h2), one small recurved seta and one longer and distally hirsute seta (h3); seta h2 less than half the length of seta h3; seta h1 not observed.

CR ( Fig. 7G ) curved and slender (thickening at proximal edge) with ventral side weakly serrated, a proximal and weakly serrated claw, a distal and weakly serrated claw, a proximal hirsute seta and a distal smooth seta. Proximal claw ¾ of the length of distal claw. Proximal seta about ⅓ of the length of distal seta.

CR attachment ( Fig. 7F ) stout, with Triebel’s loop in the middle of the distal part of main brand. Distal arc enclosing Triebel’s loop thin and acutely connecting to short db, vb well-developed.

Male

Unknown.

Measurements

See Table 2 .

Remarks

Following the generic revision by Savatenalinton & Martens (2009), the present species should be referred to the genus Bradleytriebella , mainly because of the apparent absence of a ‘d’-seta on the T1. However, because the position and validity of the S. vinciguerrae / vavrai - group as a whole should be re-assessed, we maintain this species for the time being in Strandesia s.lat.

Figures

Fig. 4. Carapace and valves of Strandesia mehesi sp. nov. ♀, paratypes; A–D: MNHN-HYNC- IU-2014-20305; E, G–H: MNHN-IU-2014-20309; F: MNHN-IU-2014-20308; I: MNHN-IU-2014- 20312. A. LVi. B. RVi. C. LVi, anterior part detail. D. RVi, anterior part detail. E. CpD. F. CpV. G. CpD, anterior part detail. H. CpD, posterior part detail. I. CpFr. Scale bars: A–B, E–F, I = 500 μm; C–D, G–H = 300 μm.

Fig. 5. Carapace and valves of Strandesia mehesi sp. nov. ♀, paratypes; A,E: MNHN-IU-2014-20310; B,G: MNHN-IU-2014-20311; C: MNHN-IU-2014-20308; D: MNHN-IU-2014-20309; F, H: MNHN- IU-2014-20312. A. CpLL. B. CpRL. C. CpRL. D. CpRL. E. CpRL. F. CpRL. G. CpRL, surface detail. H. CpRL, surface detail. Scale bars: A–F = 500 μm; G = 300 μm; H = 30 μm.

Fig. 6. Limbs of Strandesia mehesi sp. nov. ♀. A,D–E, G: holotype MNHN-HYNC-IU-2014-20304; B–C, F: paratype MNHN-IU-2014-20307. A. A1. B. A2. C. A2, distal end of penultimate segment and terminal segment. D. Md-palp. E. Md-palp, showing α, β and γ setae. F. Md-palp, terminal segment. G. Md-coxa. Scale bars: A–C, E, G = 100 μm; D, F = 60 μm.

Fig. 7. Limbs of Strandesia mehesi sp. nov. ♀. A–E: holotype MNHN-HYNC-IU-2014-20304; F: paratype MNHN-IU-2014-20307; G: paratype MNHN-IU-2014-20306. A. Mx1. B. T1, protopodite. C. T2. D. T3. E. T3, apical pincer. F. CR attachment. G. CR. Scale bar: A–B = 60 μm; C–D = 100 μm; E = 200 μm; F–G = 150 μm.