A New Species of Centrohelid Heliozoan Acanthocystis amura n. sp. Isolated From Two Remote Locations in Russia.

Abstract

A new species of centrohelid heliozoan Acanthocystisamura from the Amur River, the Far East of Russia was studied with light- and electron microscopy. Acanthocystis amura has simple oval plate scales (1.2-2.6×1.0-1.8μm) with an axial thickening and a thin border as well as two types of spine scales. The spine scales of type1 were 1.3-4.8μm long and had four small hooks on their tips. The spine scales of type2were shorter, 1.0-3.6μm long and had four teeth at the distal end. The morphology of A.amura resembles that of Acanthocystisquadrifurca. They both have similar spine scales but their plate scales are completely different. Acanthocystisvaldiviense differs from the new species in absence of hook-bearing scales. Molecular phylogeny based on 18SrDNA consistently placed A.amura into Acanthocystis nichollsi/Acanthocystis costata clade, but relationships between those three species were not resolved. Morphology of another centrohelid strain from another location (the South Urals) has been compared with that of the original strain and few minor differences in size characteristics of the scales have been revealed.