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We conducted microcosm experiments with two contrasting freshwater ciliates on functional traits (FTs) related to their growth rate (numerical response, NR) and ingestion rate (functional response, FR) over a range of ecologically relevant temperatures. Histiobalantium bodamicum and Vorticella natans are common planktonic ciliates but their abundance, swimming behavior, and temperature tolerance are different. In contrast to most sessile peritrich species, the motile V. natans is not strictly bacterivorous but also voraciously feeds upon small algae. We observed three main alterations in the shape of NR of both species with temperature, that is, change in the maximum growth rate, in the initial slope and in the threshold food level needed to sustain the population. Similarly, maximum ingestion rate, gross growth efficiency (GGE), and cell size varied with temperature and species. These findings caution against generalizing ciliate performance in relation to the ongoing global warming. Our results suggest that V. natans is the superior competitor to H. bodamicum in terms of temperature tolerance and bottom-up control. However, the abundance of V. natans is usually low compared to H. bodamicum and other common freshwater ciliates, suggesting that V. natans is more strongly top-down controlled via predation than H. bodamicum. The taxonomic position of V. natans has been debated. Therefore, to confirm species and genus affiliation of our study objects, we sequenced their small subunit ribosomal RNA (SSU rDNA) gene. IT has been known for decades that protists represent central nodes in aquatic food webs (Fenchel 1987). As primary producers, predators, food, and parasites, they are structural elements of any aquatic food web and are of tremendous global and local significance for cycling of matter in the ocean and inland water bodies (

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Background: Hypotrichia are a group with the most complex morphology and morphogenesis within the ciliated protists. The classification of Gastrostyla-like species, a taxonomically difficult group of hypotrichs with a common ventral cirral pattern but various dorsal and ontogenetic patterns, is poorly understood. Hence, systematic relationships within this group and with other taxa in the subclass Hypotrichia remain unresolved. Results: 18S rRNA gene sequence of a new Gastrostyla-like taxon was obtained. Phylogenetic analyses based on the 18S rRNA gene sequences indicate that this ciliate represents a new genus that is closely related to Heterourosomoida and Kleinstyla within the oxytrichid clade of the Hypotrichia. However, the position of this cluster remains unresolved. All three genera deviate from the typical oxytrichids by their incomplete (or lack of) dorsal kinety fragmentation during morphogenesis. Morphology and morphogenesis of this newly discovered form, Heterogastrostyla salina nov. gen., nov. spec., are described. Heterogastrostyla nov. gen., is characterised as follows: more than 18 fronto-ventral-transverse cirri, cirral anlagen V and VI develop pretransverse cirri, and dorsal ciliature in Urosomoida-like pattern. Conclusions: Similar to the CEUU-hypothesis about convergent evolution of urostylids and uroleptids, we speculate that the shared ventral cirral patterns of Gastrostyla-like taxa might have resulted from convergent evolution.

In the five years 2012-2016, the ciliate research group at Ocean University of China and their collaborators have performed several investigations on the morphogenesis of ciliated protists during binary division. Multiple samples were collected from 17 cities and cortical development studied in 42 species belonging to 32 genera and 13 families (Amphisiellidae, Euplotidae, Kahliellidae, Oxytrichidae, Philasteridae, Pseudokeronopsidae, Pseudourostylidae, Schmidingerotrichidae, Spirofilidae, Strobilidiidae, Uroleptidae, Uronychiidae and Urostylidae). Among these, 12 genera were investigated morphogenetically for the first time, revealing some unusual pattern formations and allowing four new genera to be established: Heterokeronopsis, Apobakuella, Parabistichella and Apoholosticha. The objective of this review is to: 1) summarize the morphogenetic studies supported by the IRCN-BC and NSFC projects during these five years; 2) summarize the patterns of development and document deviations from normal morphogenetic events within a group; 3) discuss how studies on morphogenesis have helped to advance understanding in the three dimensions of biodiversity, i.e. taxonomy, genetics and function; and 4) suggest potential future directions for the morphogenetic study of ciliated protists.