Massisteria marina has a sister: Massisteria voersi sp. nov., a rare species isolated from coastal waters of the Baltic Sea

Abstract

For many years, the genus Massisteria (Cercozoa, Leucodictyida) comprised only one species, M. marina. This small species has a biphasic life cycle and feeds through filose, radiating pseudopodia. It has a distinct swimming form and is regularly detected in association with detritus aggregates. However, environmental sequences closely related to this species indicate a larger species richness than hitherto described for the genus Massisteria. Here we provide the first report of Massisteria voersi sp. nov., investigated with microscopic and molecular methods. Several strains of this new species were isolated from brackish water at a Baltic Sea coastal monitoring station. Their characteristics are typical of the genus. Massisteria voersi differs from M. marina by smaller cell size (2.3-3 μm vs. 2.5-9 μm) and absent fused motile cells. Additionally, in contrast to M. marina, the new species lacks a paranuclear body and its kinetosomes are arranged in parallel. Both species are quite distantly related regarding their 18S rRNA gene sequences. The sparse availability of environmental sequences closely related to M. voersi as well as our preliminary results from fluorescence in situ hybridization studies suggest that this new species is a representative of low-abundance populations comprising the so-called "rare biosphere."

Keywords: Benthic–pelagic coupling; Brackish; Detritus; Massisteria voersi; Rare species.