Taxonomic and phylogenetic studies on two new freshwater Amphileptus species (Ciliophora, Pleurostomatida), from Lake Weishan, northern China

The morphology and phylogeny of two new species of pleurostomatid ciliates, Amphilepus weishanensis sp. nov. and A. parapleurosigma sp. nov., collected from Lake Weishan in northern China, were studied using live observation, protargol staining and phylogenetic analyses based on small subunit ribosomal DNA (SSU rDNA) sequence data. In both species, extrusomes form an apical group and contractile vacuoles are distributed along both the dorsal and the ventral margin. Amphileptus weishanensis sp. nov. is characterized by its body size (560-780 x 60-100 lm in vivo) and the possession of five left and 56-61 right somatic kineties, filiform extrusomes and 3-9 macronuclear nodules. Amphileptus parapleurosigma sp. nov. is characterized by possessing 4-6 left and 19-24 right somatic kineties and clavate extrusomes. The SSU rDNA sequences differ among ten similar species by 3-60 bp. Phylogenetic analyses based on the SSU rDNA sequences indicate that the family Amphileptidae is monophyletic while Amphileptus is paraphyletic with Pseudoamphileptus nesting within this genus. (C) 2021 Elsevier GmbH. All rights reserved.