Tonnacypris edlundi, Meeren, Thijs Van Der, Khand, Yondon & Martens, Koen, 2009

Meeren, Thijs Van Der, Khand, Yondon & Martens, Koen, 2009, On Recent species of To n n a c y p r i s Diebel & Pietrzeniuk, 1975 (Crustacea, Ostracoda), with new species descriptions from Mongolia, Zootaxa 2015, pp. 1-41 : 16-22

Tonnacypris edlundi n. sp.

( Figs. 2 C, 5B, 10, 11, 12, 13, 21)

Type locality. Grassy outflow stream from Bakhlagiin spring (49°10’46”N, 90°17’03”E). No water chemistry data is available for the type locality itself, but a nearby site (49°11’30”N, 90°14’14”E) at the source of the spring also contained this species: pH 7.9; conductivity 1222 µS/cm (corrected to 25°C); TDS 876 mg /L; T 6.3°C, DO 11.5 mg /L.

Type material. Holotype: male (OC.2988), soft parts dissected in glycerin in a sealed slide, valves stored dry in a micropalaeontological slide. Dimensions: L = 1.25 mm, H = 677 µm.

Allotype: female (OC.2989), dissected and stored in the same way as holotype. Dimensions: L = 1.32 mm, H = 687 µm.

Paratypes: OC. 2990–2997 (most specimens dissected and used for SEM, some whole animals preserved in 70% EtOH).

Material examined. Specimens were retrieved from several sites in western Mongolia (Table 1). SEM images are presented for OC. 2990, 2994, 2995 and drawings of soft parts are included for OC.2990, 2992.

Derivation of the name. This species is named after Mark Edlund (Science Museum of Minnesota, Minneapolis), in recognition of his scientific contributions to the taxonomy and ecology of Mongolian diatoms.

Diagnosis. Moderately large species (females up to 1.5 mm); anterior and posterior margins broadly rounded; inner lamella of the LV with one anteroventral and one posteroventral peg, anteroventral peg associated with a reduced inner list. A2 with long natatory setae, tips usually slightly exceeding the terminal claws. Mx1 with tooth bristles of the third masticatory endite smooth; terminal segment of the right clasping palp of the male stout and distinctly triangular.

Description of male. Valves in lateral view with greatest height just anteriorly of midlength; LV overlapping RV ventrally; anterior margin broadly rounded, posterodorsal margin sloping, inconspicuous posterodorsal angle proceeding to widely curved and evenly rounded posterior margin; valves in dorsal view elongated subovate with greatest width at midlength; LV overlaps RV at both ends, which are slightly pointed; valves in inner view ( Fig. 10 A, B) with ventral margin only slightly concave; dorsal margin sloping almost straight between highest point and posterodorsal angle; calcareous part of the inner lamella anteriorly broad, more than twice as broad as posteriorly, ventrally narrow; in LV posterdorsal angle slightly less pronounced and two pegs on the ventral side of the calified inner lamella, the anterior peg associated with reduced inner list; few marginal pores with simple, straight setae and simple, straight radial pore canals; false pore canals branching ( Fig. 2 C); colour: whitish.

A1 with Wouters organ small, protruding and lobe-like; Rome organ small; terminal segment with two long setae, one short claw, and one small, slender Y-aesthetasc.

A2 ( Fig. 11 A) with natatory setae just reaching or reaching slightly beyond distal end of terminal claws; apical chaetotaxy: z1 and z2 longest claws, z3 a long seta, G1 a small claw, G2 a long claw (slightly shorter than z1 and z2), G3 a small seta; terminal segment with long claw GM, shorter claw Gm, seta g, aesthetasc y3 with a seta fused at the base of this aesthetasc; last two segments apically with protruding reinforcements surrounding the socket of the largest claws.

Md palp with short, smooth α-seta; a group of three smooth setae and one barbed seta associated with serrated β-seta, which is slightly longer than the α-seta; and equally long, slightly stouter, serrated γ-seta.

Mx1 with eight (5+3) setae on the first segment of the palp; terminal segment of this palp spatulate; tooth bristles of third endite smooth; sideways-directed bristles serrated.

T1 protopodite with at the basal part two a-setae, single b, c and d-seta, masticatory process with 14 setae; exopodite a respiratory plate with six plumose filaments; endopodite developed asymmetrical as twosegmented palp with clasping function: penultimate segment of the right palp stout, rectangular and bearing two peg-like, subequal sensory organs ( Fig. 11 B), penultimate segment of the left clasping palp elongated, rectangular and bearing two smaller, unequal sensory organs ( Fig. 11 C); terminal segment of the right clasping palp ( Fig. 11 B) stout and distinctly triangular, of left clasping palp ( Fig. 11 C) sickle-shaped and tapering towards distal end, both terminal segments have distally a sensory organ.

T2 with length of seta d1 about 0.75–1.0 length of seta d2; teeth on terminal claw quite large.

CR ( Fig. 11 F) with proximal seta slightly hirsute, proximal slightly enforced; distal setae relatively long; posterior part of the ramus almost completely set with>10 fields of setulae.

Hemipenis ( Fig. 11 D) with outer lobe curved, distally tapering and bluntly pointed, reaching only slightly beyond the inner lobe; the latter broadly rounded; Zenker’s organ muscular with numerous internal spines ( Fig. 11 E).

A dditional description of female. Valves in lateral view ( Fig. 10 C,D) as in the male, but larger in all dimensions; ventral indentation slightly less pronounced and posterodorsal angle slightly wider than in the male; carapace in dorsal view ( Fig. 10 E) subovate and slightly pointed at anterior side, more evenly rounded at posterior side; pore canals straight and simple ( Fig. 10 F), false pore canals branching ( Fig. 2 C); colour: whitish.

A1 ( Fig. 12 A) as in male.

A2 ( Fig. 12 B) with natatory setae long, the longest usually reaching slightly beyond the proximal edge of the terminal segment; G1 and G3 long terminal claws, G2-claw slightly shorter, about four-fifth of the length of G1; z1-seta slightly shorter than G2, z2 and z3 setae subequal in length with G2.

Mdpalp ( Fig. 12 C) as in male.

Mx1 ( Fig. 13 B) as in male.

T1 ( Fig. 13 C) protopodite, masticatory process and exopodite as in male; endopodite an unsegmented palp with three unequal apical setae.

T2 (female with slightly less developed teeth on terminal claw Fig. 13 D), T3 ( Fig. 13 E, F) and CR ( Fig. 13 G, H and Fig. 5 B) basically as described for the male.

Measurements. Female: L = 1.30–1.52 mm (n = 5), H = 687–840 µm (n = 5), W = 670–678 µm (n = 2) Male: L = 1.20–1.31 mm (n = 4), H = 632–733 µm (n = 4)

Ecology. This species was found in a spring and the associated stream outflow, in two streamlets also close to the spring discharge, and also in two wetlands associated with nearby streams (Table 1). With the natatory setae being unusually long for this genus, this species should be quite mobile, especially in flowing waters. Temperature of the water of the various habitats in which the species was found: 6.0–15.5°C, pH 7.5–7.9 and conductivity 500–1270 µS/cm. Altitude: 1057–1946 m. In the type locality, where also a lot of juveniles were found, sex ratio was close to 1:1 (14 ɗ and 12 Ψ recovered). The present populations of this species could thus have an obligatory sexual reproduction.

Differential diagnosis.

The species is distinguished from:

Tonnacypris estonica by its slightly higher valves, anterior and posterior pegs on the inner lamella of LV, long natatory setae on A2 and slender proximal setae of CR.

Tonnacypris tonnensis by its smaller size, rounded posterior margin, long claw G2 on A2, long natatory setae on A2, group of three setae next to β seta on Md palp, long γ seta on Md palp and eight setae on the first segment of Mx palp.

Tonnacypris mazepovae n. sp. by its smaller size, broader anterior calcified lamella, long claw G2 on A2, long natatory setae on A2, group of three setae next to β seta on Md palp, smooth tooth bristles on the third endite of Mx, eight setae on the first segment of Mx palp and stout, distinctly triangular terminal segment of the right clasping palp of the male, which lacks an indentation near the basis.

Tonnacypris glacialis by its smaller size, anterior and posterior pegs on the calcified lamella of LV, long claw G2 on A2, long natatory setae on A2, group of three setae next to β seta on Md palp, smooth tooth bristles on the third endite of Mx, eight setae on the first segment of Mx palp and stout, distinctly triangular terminal segment of the right clasping palp of the male.

Tonnacypris lutaria by its smaller size, anterior and posterior pegs on the calcified lamella of LV, long claw G2 on A2, long natatory setae on A2, group of three setae next to β seta on Md palp, smooth tooth bristles on the third endite of Mx, eight setae on the first segment of Mx palp and stout, distinctly triangular terminal segment of the right claping palp of the male.

Figures

FIGURE 2. Detail of the anteroventral marginal valve zones with indication of true pore canals (t) and false pore canals (f) A) Tonnacypris estonica; B) Tonnacypris tonnensis; C) Tonnacypris edlundi n. sp. Scale = 50 µm.

FIGURE 5. Detail of apical chaetotaxy of CR Ψ A) Tonnacypris tonnensis (OC. 3002); B) Tonnacypris edlundi n. sp (OC. 2995); C) Tonnacypris lutaria (OC. 3003); D) Tonnacypris estonica (OC. 3000). Scale: A = 62,5 µm; B, D = 50 µm; C = 66,6 µm.

FIGURE 10. Tonnacypris edlundi n. sp. ♂ (A, B) and Ψ (C – I): A) RV, iv (OC. 2994); B) LV, iv (OC. 2994); C) RV, iv (OC. 2995); D) LV, iv (OC. 2995); E) Cp, dorsal view (OC. 3009); F) detail pore canals; G) LV, iv from dorsal side under an angle of about 45 ° (OC. 2990); H) idem, detail anteroventral peg; I) idem, detail posteroventral peg. Scale: C – E = 500 µm; A, B, G = 200 µm; H, I = 20 µm.

FIGURE 11. Tonnacypris edlundi n. sp. ♂ A) A 2, with indication of aesthetascs Y, y 1, y 2, y 3 and claws z 1, z 2, G 1, G 2, GM, Gm and setae z 3, G 3, g; B) T 1, right clasping palp; C) T 1, left clasping palp; D) Hemipenis, with internal structures; E) Zenker’s organ; F) CR and attachment. Scale: A = 214 µm; B, C = 150 µm; D = 291 µm F = 188 µm; E = 300 µm. (OC. 2990)

FIGURE 12. Tonnacypris edlundi n. sp. Ψ A) A 1, with indication of Rome organ (R), aesthetasc Ya and detail of Wouters organ; B) A 2, with indication of aesthetascs Y, y 1, y 2, y 3 and claws G 1, G 2, G 3, GM, Gm and setae z 1, z 2, z 3, g; C) Md palp, with indication of setae α, β, γ. Scale: A = 200 µm, inset = 10 µm; B = 141 µm; C = 100 µm. (OC. 2992)

FIGURE 13. Tonnacypris edlundi n. sp. Ψ A) Md (plate) B) Mx 1, with indication of number of setae on the first segment of the palp, endites incompletely drawn; C) T 1, with indication of setae a, b, c, d; D) T 2, with indication of setae d 1 and d 2; E) T 3; F) T 3, detail of apical structures (Pincer’s organ); G) CR; H) attachment of CR. Scale: A, D, E, G, H = 200 µm; B = 100 µm; C = 141 µm; F = 40 µm. (OC. 2992)