Phagotrophic protists are diverse and abundant in aquatic and terrestrial environments, making them fundamental to the transfer of matter/energy within their respective food webs. Recognising their grazing impact is essential to evaluate the role of protists in ecosystems, and this includes appreciating prey selectivity. Efforts have been made by groups and individuals to understand selective grazing behaviour by protists: many approaches and perspectives have been pursued, not all of which are compatible. This article, which is not a review, is the product of our discourse on this subject at the SAME 10 meeting. It is the work of individuals, assembled for their breadth of backgrounds, approaches, views, and expertise. Firstly, to communicate ideas and approaches, we develop a framework for selective feeding processes and suggest 6 steps: searching, contact, capture, processing, ingestion, digestion. We then separate study approaches into 2 categories: (1) those examining whole organisms at the community, population, and individual levels, and (2) those examining physiology and molecular attributes. Finally, we explore general problems associated with the field of protistan selective feeding (e.g. linking food selection into food webs and modeling). We do not present all views on any one topic, nor do we cover all topics; instead, we offer opinions and suggest avenues for continued study. Overall, this paper should stimulate further discourse on the subject and provide a roadmap for the future

In late summer 1993 an intensive study was carried out on protozoan grazing in the epilimnion and metalimnion of the eutrophic Rímov Reservoir in south Bohemia. On average, ∼ 70% of bacterial production was consumed by heterotrophic flagellates and 20% by ciliates. Ciliate numbers increased from 5 to 70 cells ml⁻¹ over the 5‐week study period. Ciliates <30 µm in size were numerically dominant in both layers and included Halteria grandinella and Strobilidium hexakinetum (Oligotrichida), Cyrtolophosis mucicola (Cyrtolophosida), Cinetochilum margaritaceum (Scuticociliatida), Urotricha spp., and Coleps sp. (Prostomatida). Ciliate species‐specific grazing rates on bacteria and picocyanobacteria were determined. The highest individual cell grazing rates, 4,200 bacteria and 560 picocyanobacteria cell⁻¹ h⁻¹, were observed in Vorticella aquadulcis‐complex. Oligotrichs ingested on average 360–2,130 bacteria and 76–210 picocyanobacteria cell⁻¹ h⁻¹, with H. grandinella (1,560 bacteria cell⁻¹ h⁻¹), due to its high abundance, as the most important ciliate bacterivore within the system. C. mucicola ingested on average 173 bacteria and 27 cyanobacteria cell⁻¹ h⁻¹; C. margaritaceum, 57 bacteria and 7 picocyanobacteria cell⁻¹ h⁻¹; and prostomatids, 23–100 bacteria and 2–14 picocyanobacteria cell⁻¹ h⁻¹. Although there was a tight relationship between grazing rates on bacteria and picocyanobacteria (r = 0.89, n = 12, P < 0.001), most of the ciliate species preferred larger picoplankton (i.e. picocyanobacteria), as indicated by their clearance rates. According to our data, several oligotrichous ciliate species and Cyclidium sp. can grow in pelagic conditions and exclusively on picoplankton food at rates of one doubling every 24–75 h.

Recent advances in molecular technology have revolutionized research on all aspects of the biology of organisms, including ciliates, and created unprecedented opportunities for pursuing a more integrative approach to investigations of biodiversity. However, this goal is complicated by large gaps and inconsistencies that still exist in the foundation of basic information about biodiversity of ciliates. The present paper reviews issues relating to the taxonomy of ciliates and presents specific recommendations for best practice in the observation and documentation of their biodiversity. This effort stems from a workshop that explored ways to implement six Grand Challenges proposed by the International Research Coordination Network for Biodiversity of Ciliates (IRCN‐BC). As part of its commitment to strengthening the knowledge base that supports research on biodiversity of ciliates, the IRCN‐BC proposes to populate The Ciliate Guide, an online database, with biodiversity‐related data and metadata to create a resource that will facilitate accurate taxonomic identifications and promote sharing of data.

Investigations on pelagic food webs in mountain lakes - aims and methods

We studied the phylogenetic diversity of nonmarine picocyanobacteria broadening the sequence data set with 43 new sequences of the 16S rRNA gene. The