Acanthocystis lyra, Gerasimova & Plotnikov, 2016

Gerasimova, Elena A. & Plotnikov, Andrey O., 2016, New Freshwater Species of Centrohelids Acanthocystis lyra sp. nov. and Acanthocystis siemensmae sp. nov. (Haptista, Heliozoa, Centrohelea) from the South Urals, Russia, Acta Protozoologica 55 (4), pp. 231-237 : 232-233

Acanthocystis lyra sp. nov. ( Figs 1 , 3 A–C )

Diagnosis: Cells are 21.0–30.0 µm (mean 26.0) in diameter. A cell coat consists of plate scales of a single type, as well as long and short spine scales. The spine scales have cylindrical shafts, branching apices and circular basal plates with a clearly expressed marginal rim. The long spine scales have a length 5.1–14.0 μm. The scale apices are divided into two pointed, deflected Sshaped branches 0.47–1.42 μm long. Both branches due to their curves form a lyrate distal end. The inner edge of each branch has 6–8 short teeth, whereas the outer edge is smooth. Basal plates of the long spine scales are 0.6–1.5 μm. The short spine scales are 1.9–3.7 μm long, broadly bifurcate at their apices. The scales possess marked primary and secondary bifurcations. Each apex of the secondary branch has two short teeth. Basal plates of the short spine scales are 0.6–1.2 μm in diameter. The plate scales are elliptical 2.4–4.1 × 1.4–2.5 μm, ornamented with an axial thickening in the central part.

Comparisons with similar species: A. cornuta Dürrschmidt, 1987 is similar to A. lyra in the structure of its long spine scales. The spine scales of A. cornuta are divided into two branches. Each branch has 2–4 teeth on the inner surface, whereas branches of A. lyra have 6–8 teeth on the inner surface. In addition, A. cornuta has spine scales of one type and plate scales ornamented with an axial thickening and radial ribs unlike A. lyra .

Branching spine scales are also known in A. bicornis Dürrschmidt, 1987 . Long scales of A. bicornis are divided into two branches. Each branch has a tooth on the inner surface, whereas branch of A. lyra has 6–8 teeth. Short scales of A. bicornis with broadly bifurcate branches have two teeth of different length on the apices of each branch. In contrast to A. bicornis , the short scales of A. lyra possess secondary bifurcation and two teeth at apices of the secondary branches. Plate scales of both A. bicornis and A. lyra have similar structure.

Etymology: The species group name lyra (from the Latin lyra ; lyre, a stringed musical instrument) refers to the apex of long spine scale looking like lyre.

Type locality: Bottom sediment from the Pismenka River , Kidryasovo settlement, the South Urals, South- East of European part of Russia, 51°15′41N, 57°28′42E. Collected 11.05.2014 .

Hapantotype: Preparation #37 ( Fig. 1 ) has been deposited in the Laboratory of Microbiology, Institute for Biology of Inland Waters of Russian Academy of Sci- ences (Borok, Russia).

ZooBank LSID: urn:lsid:zoobank.org:act:81FC70D5-E430-425E-8498-AF14610222B8

Figures

Fig. 1. SEM of Acanthocystis lyra sp. nov.A – General view of the scales.B – Long spine scale. C – Lyrate distal end of long spine scale with teeth on inner edge. D – Short spine scale with secondary bifurcation. E – Short spine scale with primary bifurcation and teeth. F – Short spine scales with primary and secondary bifurcations.A marginal rim is seen on basal plates of short and long spine scales. G – Plate scales ornamented with an axial thickening. Abbreviations: at – axial thickening; b1 – primary bifurcation; b2 – secondary bifurcation; bp – basal plate; br – branch of furca; mr1 – marginal rim on basal plate of short spine scale; mr2 – marginal rim on basal plate of long spine scale; sh – shaft; t – teeth. Scale bars: A – 10 µm; B, D, E, F, G – 1 µm; C – 0.5 µm.

Fig. 3. Line drawings of scales of Acanthocystis lyra sp. nov. (A–C) and Acanthocystis siemensmae sp. nov. (D–F):A, D – long spine scales; B, E – short spine scales; C, F – plate scales.