Pterocystis caudata sp. n. – the new species of centrohelid heliozoans (Pterocystidae, Pterocystida, Centroplasthelida) from the Bay of Villefranche, France

Abstract

A new species of centrohelid heliozoans Pterocystis caudata sp. n. from the Bay of Villefranche (France) was studied with light and electron microscopy. The cell diameter is 7.6–19.0 (av. 12.4) µm. P. caudata has scales of two distinct types. Plate scales (2.08–3.48 (av. 2.6) × 1.07–1.65 (av. 1.3) µm) are flat, oval, with parallel edges and axial thickening. Spine scales (2.47–7.1 (av. 4.6) µm) with a funnel-shaped base, which is indistinctly continuous with a shaft. The shaft demonstrates gradual levels of reduction; in some scales it is completely absent. The surface of the spine scales is smooth, ornamented with few slits at the base of the shaft and on the surface of the funnel and has a thin marginal border. The cells are floating or attached to the substratum, sometimes in aggregates of 2–3 cells. The species diversity of Pterocystis spp. with leaf-shaped and scoop-shaped spine scales is discussed.