Tonnacypris glacialis ( Sars, 1890 )

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 : 28-29

Tonnacypris glacialis ( Sars, 1890)

( Fig. 18 , 21 , 22 D–F)

Herpetocypris glacialis Sars, 1890 (p.61; fig. 1)

Eucypris glacialis (Sars) Vávra, 1891

Prionocypris glacialis (Sars) Brady & Norman, 1896 (figs. 50–68) Eucypris glacialis (Sars) Bronshstein, 1947 (p.126; figs. 53, 54) Tonnacypris glacialis (Sars) Griffiths, 1995 (p. 523)

Material examined. Three dissected females from Svaldbard. Valves were completely decalcified and hence destroyed during dissection. Drawings of soft parts are included for OC.3027, 3028.

Additional description of female. For description and illustrations of valves, we refer to Griffiths et al. (1998). The material presented here was too decalcified to be able to give additional valve characters.

A2 ( Fig. 18 A) with reduced natatory setae, third seta the longest and reaching the basis of the terminal segment; z1 a short setae, z2 and z3 long setae, G1 and G3 long claws, G2 a short claw (about 1.6 times the length of the terminal segment); terminal segment with a long claw GM, shorter claw Gm, seta g, and aesthetasc y3, with seta fused at the base with this aesthetasc.

Md palp with slender α-seta on the first segment, a strongly developed and serrated β-seta flanked by a group of four smooth seta on the second segment, and a long, serrated γ-seta on the penultimate segment ( Fig. 18 C).

Mx1 with seven (5+2) setae on the first segment of the palp, tooth bristles on the third endite serrated.

T2 ( Fig. 18 B) with seta d1 reduced and seta d2 of normal length.

CR ( Fig. 18 D) with proximal seta slightly hirsute, proximally slightly enforced; distal half of the posterior side of the ramus set with about six setular fields, these fields slightly wider than in the other species of the genus (2 or 3 parallel rows of setulae instead of 1 or 2).

Measurements. Female: length = 1.56–1.68 mm (n = 3)

Remarks. Griffiths et al. (1998) gave a whole range of measurements for Recent and Pleistocene populations. Most of these measurements of adult (sub-) Recent specimens fall in the range of 1.40–1.75 mm for the length and 710–900 µm for the height. They also suggested that the presence of this species indicates mean summer (June–August) temperatures of about 6° C. Bronshtein (1947) reports carapace lengths of up to 1.6 mm.

Figures

FIGURE 18. Tonnacypris glacialis Ψ A) 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 (OC. 3027); B) T 2, with indication of setae d 1 and d 2 (OC. 3027); C) Md palp, detail of setae α, β, γ, incompletely drawn (OC. 3028); D) CR with attachment (OC. 3027). Scale: A, D = 100 µm; B = 148 µm; C = 39 µm.

FIGURE 21. Length-height plot for Tonnacypris species in this study.

FIGURE 22. Tonnacypris cf. lutaria ♂ and T. glacialis ♂ A) T 1, left clasping palp; B) T 1, right clasping palp; C) Hemipenis, with indication of internal structures; D) T 1, left clasping palp; E) T 1, right clasping palp; F) Hemipenis, with indication of internal structures. A – C redrawn after Akatova 1950; D – F redrawn after Bronshtein 1947.