@article{ParaskevopoulouTiedemannWeithoff2018,
  author    = {Paraskevopoulou, Sofia and Tiedemann, Ralph and Weithoff, Guntram},
  title     = {Differential response to heat stress among evolutionary lineages of an aquatic invertebrate species complex},
  series = {Biology letters},
  volume    = {14},
  journal   = {Biology letters},
  number    = {11},
  publisher = {Royal Society},
  address   = {London},
  issn      = {1744-9561},
  doi       = {10.1098/rsbl.2018.0498},
  pages     = {5},
  year      = {2018},
  abstract  = {Under global warming scenarios, rising temperatures can constitute heat stress to which species may respond differentially. Within a described species, knowledge on cryptic diversity is of further relevance, as different lineages/cryptic species may respond differentially to environmental change. The Brachionus calyciflorus species complex (Rotifera), which was recently described using integrative taxonomy, is an essential component of aquatic ecosystems. Here, we tested the hypothesis that these (formerly cryptic) species differ in their heat tolerance. We assigned 47 clones with nuclear ITS1 (nuITS1) and mitochondrial COI (mtCOI) markers to evolutionary lineages, now named B. calyciflorus sensu stricto (s.s.) and B. fernandoi. We selected 15 representative clones and assessed their heat tolerance as a bi-dimensional phenotypic trait affected by both the intensity and duration of heat stress. We found two distinct groups, with B. calyciflorus s.s. clones having higher heat tolerance than the novel species B. fernandoi. This apparent temperature specialization among former cryptic species underscores the necessity of a sound species delimitation and assignment, when organismal responses to environmental changes are investigated.},
  language  = {en}
}
@article{ColangeliSchlaegelOberteggeretal.2019,
  author    = {Colangeli, Pierluigi and Schl{\"a}gel, Ulrike E. and Obertegger, Ulrike and Petermann, Jana S. and Tiedemann, Ralph and Weithoff, Guntram},
  title     = {Negative phototactic response to UVR in three cosmopolitan rotifers: a video analysis approach},
  series = {Hydrobiologia : acta hydrobiologica, hydrographica, limnologica et protistologica},
  volume    = {844},
  journal   = {Hydrobiologia : acta hydrobiologica, hydrographica, limnologica et protistologica},
  number    = {1},
  publisher = {Springer},
  address   = {Dordrecht},
  issn      = {0018-8158},
  doi       = {10.1007/s10750-018-3801-y},
  pages     = {43 -- 54},
  year      = {2019},
  language  = {en}
}
@article{DragoPawlakWeithoff2020,
  author    = {Drago, Claudia and Pawlak, Julia and Weithoff, Guntram},
  title     = {Biogenic aggregation of small microplastics alters their ingestion by a common freshwater micro-invertebrate},
  series = {Frontiers in Environmental Science},
  volume    = {8},
  journal   = {Frontiers in Environmental Science},
  publisher = {Frontiers Media},
  address   = {Lausanne},
  issn      = {2296-665X},
  doi       = {10.3389/fenvs.2020.574274},
  pages     = {11},
  year      = {2020},
  abstract  = {In recent years, increasing concerns have been raised about the environmental risk of microplastics in freshwater ecosystems. Small microplastics enter the water either directly or accumulate through disintegration of larger plastic particles. These particles might then be ingested by filter-feeding zooplankton, such as rotifers. Particles released into the water may also interact with the biota through the formation of aggregates, which might alter the uptake by zooplankton. In this study, we tested for size-specific aggregation of polystyrene microspheres and their ingestion by a common freshwater rotifer Brachionus calyciflorus. The ingestion of three sizes of polystyrene microspheres (MS) 1-, 3-, and 6-mu m was investigated. Each MS size was tested in combination with three different treatments: MS as the sole food intake, MS in association with food algae and MS aggregated with biogenic matter. After 72 h incubation in pre-filtered natural river water, the majority of the 1-mu m spheres occurred as aggregates. The larger the particles, the higher the relative number of single particles and the larger the aggregates. All particles were ingested by the rotifer following a Type-II functional response. The presence of algae did not influence the ingestion of the MS for all three sizes. The biogenic aggregation of microspheres led to a significant size-dependent alteration in their ingestion. Rotifers ingested more microspheres (MS) when exposed to aggregated 1- and 3-mu m MS as compared to single spheres, whereas fewer aggregated 6-mu m spheres were ingested. This indicates that the small particles when aggregated were in an effective size range for Brachionus, while the aggregated larger spheres became too large to be efficiently ingested. These observations provide the first evidence of a size- and aggregation-dependent feeding interaction between microplastics and rotifers. Microplastics when aggregated with biogenic particles in a natural environment can rapidly change their size-dependent availability. The aggregation properties of microplastics should be taken into account when performing experiments mimicking the natural environment.},
  language  = {en}
}
@article{DragoWeithoff2021,
  author    = {Drago, Claudia and Weithoff, Guntram},
  title     = {Variable Fitness Response of Two Rotifer Species Exposed to Microplastics Particles},
  series = {Toxics},
  volume    = {9},
  journal   = {Toxics},
  number    = {11},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2305-6304},
  doi       = {10.3390/toxics9110305},
  pages     = {13},
  year      = {2021},
  abstract  = {Plastic pollution is an increasing environmental problem, but a comprehensive understanding of its effect in the environment is still missing. The wide variety of size, shape, and polymer composition of plastics impedes an adequate risk assessment. We investigated the effect of differently sized polystyrene beads (1-, 3-, 6-µm; PS) and polyamide fragments (5-25 µm, PA) and non-plastics items such as silica beads (3-µm, SiO2) on the population growth, reproduction (egg ratio), and survival of two common aquatic micro invertebrates: the rotifer species Brachionus calyciflorus and Brachionus fernandoi. The MPs were combined with food quantity, limiting and saturating food concentration, and with food of different quality. We found variable fitness responses with a significant effect of 3-µm PS on the population growth rate in both rotifer species with respect to food quantity. An interaction between the food quality and the MPs treatments was found in the reproduction of B. calyciflorus. PA and SiO2 beads had no effect on fitness response. This study provides further evidence of the indirect effect of MPs in planktonic rotifers and the importance of testing different environmental conditions that could influence the effect of MPs.},
  language  = {en}
}
@article{ParrySchlaegelTiedemannetal.2022,
  author    = {Parry, Victor and Schl{\"a}gel, Ulrike E. and Tiedemann, Ralph and Weithoff, Guntram},
  title     = {Behavioural Responses of Defended and Undefended Prey to Their Predator},
  series = {Biology},
  volume    = {11},
  journal   = {Biology},
  number    = {8},
  publisher = {MDPI},
  address   = {Basel, Schweiz},
  issn      = {2079-7737},
  doi       = {10.3390/biology11081217},
  pages     = {14},
  year      = {2022},
  abstract  = {Predation is a strong species interaction causing severe harm or death to prey. Thus, prey species have evolved various defence strategies to minimize predation risk, which may be immediate (e.g., a change in behaviour) or transgenerational (morphological defence structures). We studied the behaviour of two strains of a rotiferan prey (Brachionus calyciflorus) that differ in their ability to develop morphological defences in response to their predator Asplanchna brightwellii. Using video analysis, we tested: (a) if two strains differ in their response to predator presence and predator cues when both are undefended; (b) whether defended individuals respond to live predators or their cues; and (c) if the morphological defence (large spines) per se has an effect on the swimming behaviour. We found a clear increase in swimming speed for both undefended strains in predator presence. However, the defended specimens responded neither to the predator presence nor to their cues, showing that they behave indifferently to their predator when they are defended. We did not detect an effect of the spines on the swimming behaviour. Our study demonstrates a complex plastic behaviour of the prey, not only in the presence of their predator, but also with respect to their defence status.},
  language  = {en}
}
@article{ParrySchlaegelTiedemannetal.2022,
  author    = {Parry, Victor and Schl{\"a}gel, Ulrike E. and Tiedemann, Ralph and Weithoff, Guntram},
  title     = {Behavioural responses of defended and undefended prey to their predator},
  series = {Biology : open access journal},
  volume    = {11},
  journal   = {Biology : open access journal},
  number    = {8},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2079-7737},
  doi       = {10.3390/biology11081217},
  pages     = {14},
  year      = {2022},
  abstract  = {Many animals that have to cope with predation have evolved mechanisms to reduce their predation risk. One of these mechanisms is change in morphology, for example, the development of spines. These spines are induced, when mothers receive chemical signals of a predator (kairomones) and their daughters are then equipped with defensive spines. We studied the behaviour of a prey and its predator when the prey is either defended or undefended. We used common aquatic micro-invertebrates, the rotifers Brachionus calyciflorus (prey) and Asplanchna brightwellii (predator) as experimental animals. We found that undefended prey increased its swimming speed in the presence of the predator. The striking result was that the defended prey did not respond to the predator's presence. This suggests that defended prey has a different response behaviour to a predator than undefended conspecifics. Our study provides further insights into complex zooplankton predator-prey interactions. Predation is a strong species interaction causing severe harm or death to prey. Thus, prey species have evolved various defence strategies to minimize predation risk, which may be immediate (e.g., a change in behaviour) or transgenerational (morphological defence structures). We studied the behaviour of two strains of a rotiferan prey (Brachionus calyciflorus) that differ in their ability to develop morphological defences in response to their predator Asplanchna brightwellii. Using video analysis, we tested: (a) if two strains differ in their response to predator presence and predator cues when both are undefended; (b) whether defended individuals respond to live predators or their cues; and (c) if the morphological defence (large spines) per se has an effect on the swimming behaviour. We found a clear increase in swimming speed for both undefended strains in predator presence. However, the defended specimens responded neither to the predator presence nor to their cues, showing that they behave indifferently to their predator when they are defended. We did not detect an effect of the spines on the swimming behaviour. Our study demonstrates a complex plastic behaviour of the prey, not only in the presence of their predator, but also with respect to their defence status.},
  language  = {en}
}