No abstract

Hypotrichs are the most complex and highly differentiated ciliate lineages and have great potential for evolutionary novelties. Problems in hypotrich systematics are mainly due to discordance between the morphological and genetic data (mainly small subunit rRNA gene). Species with morphologies that are characteristic of two or more higher rank taxa are probably a major contributing factor to these conflicts. The present study describes a Chinese population of a poorly known organism with numerous endosymbiotic zoochlorellae, the morphology of which corresponds well with the type population of Limnoholosticha viridis (Kahl, 1932) Li et al., 2017. Newly obtained information shows this species has a zigzag midventral cirral pattern that is diagnostic of urostylids, whereas the dorsal ciliature shares features (presence of dorsomarginal kinety and dorsal kinety 3 fragmentation) that are typical of oxytrichids. Molecular phylogenetic analyses reveal a close relationship with oxytrichids. An integrative approach combining morphological, morphogenetic, phylogenetic and ecological analyses indicates that L. viridis represents a new genus and new family which might be an intermediate form between uorstylids and dorsomarginalians. Thus, Bourlandellidae fam. nov. and Bourlandella gen. nov. are here established. Lastly, we speculate that phenotypic convergence and mixtrophy might confer on the new combination, Bourlandella viridis (Kahl, 1932) comb. nov., the ability to adapt to a wide range of environmental conditions.

In the present study, based on both morphologic and phylogenetic analyses, a new genus, Monourostylopsis n. gen., and new species, Metaurostylopsis alrasheidi n. sp. as well as a new combination, Monourostylopsis antarctica (Jung et al., 2011) n. comb. (original combination: Metaurostylopsis antarcticaJung et al., 2011), are suggested. The new genus is diagnosed mainly by having three or more frontoterminal cirri, a midventral complex with midventral pairs and a single midventral row, one right marginal row and two or more left marginal rows. The new genus can be easily separated from the morphologically similar genera mainly by having single right marginal row (vs. two or more right marginal rows). Based on live observation and protargol staining, the morphology and morphogenesis of a new species, M. alrasheidi n. sp. isolated from China, were investigated. The new species can be characterized by: two types of cortical granules; about 22 adoral membranelles; three or four frontoterminal, four or five transverse cirri; about eight midventral pairs and a midventral row of three or four unpaired midventral cirri; three or four left and right marginal rows. The main morphogenetic features of Metaurostylopsis alrasheidi n. sp. can be summarized as: (1) the entire parental ciliature, including the oral apparatus, is renewed; (2) the oral primordium of the proter probably originates within a pouch; (3) the oral primordium of the opisthe forms de novo on the cell surface; (4) the anlagen of marginal rows and dorsal kineties are formed intrakinetally, and (5) the fusion of macronuclear nodules results in an irregular branched mass prior to karyokinesis. In the phylogenetic trees, all the available Metaurostylopsis sequences cluster together in a clade with full support (ML/BI: 100/1.00) revealing that the genus is monophyletic within the large group of core urostylids.