Maximum growth rate, size and commonness in a community of bactivorous ciliates

Abstract

Adaptions which confer competitive ability or resistance to predation are thought to be evolved with a resultant loss in intrinsic rate of increase (r ). Therefore species which are opportunistic should retain high values of r, whereas competitively superior species which employ a strategy of persistance will have low values of r . Whether a ciliate species is slow or fast-growing can be judged by comparison with the empirically derived equation relating growth rate and size given by Fenchel (1968).This hypothesis was tested on a group of eleven species of bactivorous ciliates inhabiting a small pond. Species' measured and predicted r'S [Formula: see text] were compared with their commonness in the field. The prediction that species with high values of [Formula: see text] would be less common, as measured by the number of samples in which they are found, was satisfied by the data. The implications of the data for the ciliate community studied and the potential of [Formula: see text] as a predictor of ecological characteristics of species are discussed.

Ecological role and bacterial grazing of Halteria spp.: small freshwater oligotrichs as dominant pelagic ciliate bacterivores

“…Both the laboratory and field experiments indicate that Halteria feeds on different trophic levels (hetero-and autotrophic picoplankton and small HNF). This likely species complex has a large prey size spectrum compared to a strictly bacterivorous species, though some authors consider, e.g., H. grandinella as primarily bacterivorous (e.g., Taylor 1978). By virtue of its omnivory and very high clearance rates on bacteria, Halteria can compete with HNF by feeding on the same food sources, moreover the ciliates can also prey on HNF (Cleven 1996, Jürgens et al 1996.…”

“…The existing evidence that Halteria can subsist on bacteria alone is contradictory: Skogstad et al (1987) and Jürgens & Š imek (2000) were not successful in cultivating members of this species complex on bacteria alone, whereas Taylor (1978) reared H. grandinella in batch cultures exclusively on a purely bacterial culture of Aerobacter aerogenes. Our analyses of food vacuole content of Halteria from both reservoirs (Table 1) indicate a rather limited importance of algae in the diet of natural populations of the ciliates.…”

“…), suggesting that phytoplankton can be an important food resource for Halteria in some lakes. On the other hand, almost the same maximum net growth rate (1.73 d -1 ) was also found when Halteria sp., reported as H. grandinella, was reared on a pure bacterial culture (Taylor 1978). Legner (1975) reported a maximum growth rate as high as 3.1 d -1 for H. grandinella growing in organically enriched samples from 2 reservoirs.…”

Interactive effect of temperature and food concentration on growth rate: A test case using the small freshwater ciliate Urotricha farcta

“…All three of these aspects of the numerical response can be combined to compare the selective advantage of different taxa on a persistence versus opportunistic strategy continuum (Taylor 1978), analogous to the r/K selection theory (MacArthur and Wilson 1967;Stemberger and Gilbert 1985;Rothhaupt 1990;Walz 1993Walz , 1995. That is, a persistent species, adapted to low food concentrations, would predictably have a low threshold concentration (xЈ), a rapid increase to its maximum growth rate (␣), and a low maximum growth rate ( max ).…”

Growth of interstitial ciliates in association with ciliate bacterivory in a sandy hyporheic zone

“…Until now, growth of ciliates has been nearly exclusively studied in the water column of freshwater or marine systems (e.g. Taylor 1978, Banse 1982, Müller & Geller 1993, Laybourn-Parry et al 2000. Growth was estimated via changes in abundance over time in laboratory investigations as well as in the field or, alternatively, by making calculations based on cell volume, temperature and maximum growth rate (e.g.…”