Klaus Hausmann

A strain of marine amoeba has been isolated and studied from the bottom sediments of the Great Meteor Seamount (Atlantic Ocean, 29°36.29′N; 28°59.12′W; 267.4 m deep). This amoeba has a typical dactylopodiid morphotype, a coat of delicate, boat-shaped scales, and a Perkinsela-like organism (PLO), an obligatory, deeply-specialized kinetoplastid symbiont near the nucleus. These characters allow us to include this species into the genus Paramoeba. However, it differs from its only described species, P. eilhardi, in the structure of scales. P. atlantica n. sp. is established therefore to accommodate the studied strain. SSU rRNA gene sequence analysis suggests that P. atlantica belongs to the Dactylopodida, and is sister to a monophyletic clade of P. eilhardi and all Neoparamoeba spp., branching separately from P. eilhardi. Therefore, the genera Paramoeba and Neoparamoeba, currently defined based on the cell surface ultrastructure, might be paraphyletic and probably should be synonymized, as further evidence is accumulated. Based on the data available we emend the families Vexilliferidae and Paramoebidae to make them more consistent with the current phylogenetic schemes.

Thecamoeba aesculea n. sp. was isolated and described from the surface of the bark of Aesculus hippocastanum and from terrestrial mosses growing on it. This amoeba is superficially similar to Thecamoeba sphaeronucleolus, but comparison of the newly isolated strain with the photographs and video records of the type strain of this species reveals differences which show that the two strains do not belong to the same morphospecies. The data obtained indicate the necessity of further comparative studies on the diversity of thecamoebian ‘morphospecies’ to outline clearer borders between them.