Prey–predator dynamics in rotifers: density‐dependent consequences of spatial heterogeneity due to surface attachment

Abstract

Abstract. Classical models of prey-predator interactions assume that per capita prey consumption is dependent on prey density alone and that prey consumption (functional response) and consumer proliferation (numerical response) operate on the same timescales and without time lags. Several modifications have been proposed for resolving this timescale discrepancy, including variants where the functional response depends on both prey and predator densities. A microcosm system with the rotifer Brachionus 'Nevada' feeding on the prasinophyte Tetraselmis sp. showed significant (P , 0.0005) increases in steady-state biomasses of both prey and predators with increasing carrying capacity (represented by total phosphorus of the growth medium), which is inconsistent with predictions based on the traditional prey-only-dependent functional response. We provide data indicating that surfaces where the predator can attach provide a high-quality habitat for rotifers, which can result in a predator-dependent functional response. We also show that partitioning between the attached and free-swimming habitats was fast compared to the timescale of the numerical response. When attached to surfaces, rotifers maximized net energy gain by avoiding the high cost of swimming and by increased food capture due to reduced viscous drag. A mathematical model with prey-dependent functional response and wall-attached and free-swimming fractions of the population describes our data adequately. We discuss the implications of this finding for extrapolating microcosm experiments to systems with other surface-to-volume ratios, and to what extent our findings may apply to other popular model organisms for prey-predator interaction.

Indirect bottom‐up control of consumer‐resource dynamics: Resource‐driven algal quality alters grazer numerical response

“…For the experiments reported here, these rotifers were fed batch-cultured Chlamydomonas reinhardtii until used in treatments. Although some species of Brachionus tend to attach to surfaces as animal density increases, which creates conditions for consumer-dependent feeding (Vadstein et al 2012), we only very rarely observed this behavior in our study, and Fussmann et al (2005) only found a consumer-dependent effect on feeding rate at unnaturally high rotifer densities.…”

Rotifera and Cladocera fauna of several lakes from the Central Anatolia,Marmara, and Western Black Sea regions of Turkey

“…The most common rotifer species observed in this study, such as Keratella quadrata, K. cochlearis, K. tecta, Polyarthra dolichoptera, P. vulgaris, and Trichocerca similis, are cosmopolitan (Segers, 2007). However, species such as Filinia longiseta and Lepadella patella, which are also known to be also cosmopolites, were observed only at one station, which might be a result of unfavorable environmental conditions and/or overpredation by fish larvae and aquatic invertebrates in these water bodies (Murtaugh, 1989;Vadstein et al, 2012). The most common Cladocera species was Bosmina longirostris, which is a well-known indicator of eutrophication (Jaramillo and Pinto, 2010).…”

High food quality of prey lowers its risk of extinction

“…A5). Additionally, lower dilution increases the importance of recycled nutrients relative to fresh supply (Vadstein et al ). This impedes the competitive ability of a low‐quality species of which a higher portion is recycled by grazing (Fig.…”