Coleps hirtus viridis was the dominant species of the planktonic ciliate community of Lake Fühlinger See (Germany) during the study in 1999 and 2000. Total ciliate densities ranged from 120 to 42,000 ind. l
−1 in 1999 and up to 8,000 ind. l
−1 in 2000.
Coleps contributed up to 98% to both total ciliate abundance and biomass and made up an average of 64% of the total ciliate biomass. Oligotrichs
(Rimostrombidium, Strobilidium) dominated the epilimnetic zone, whereas peritrich ciliates
(Pelagovorticella, Vorticella) were predominantly located in the hypolimnion. The population maximum of
Coleps changed locations from the epilimnion in early summer to the hypolimnion (up to 40,000 ind. l
−1) during stratification. High growth rates in the hypolimnion, presence of endosymbiontic algae and the ability to ingest detritus seem to be important for the success.Growth rates of
Coleps in June were determined by Landry-Hassett dilution experiments in both the epilimnion and the hypolimnion. The instantaneous growth rates were similar in both layers (0.6 d
−1), but a distinctly higher instantaneous mortality was estimated for the epilimnion. These high loss rates may be due to grazing pressure by cladocerans.The significance of the histophagous feeding of
Coleps was evaluated through an experiment using killed zooplankton. Parts of
Daphnia magna were incorporated at rates of about 1,100 μm
3 ind.
−1 h
−1 by
Coleps without endosymbiotic algae and at rates of 500 μm
3 ind.
−1 h
−1 by
Coleps with endosymbionts. These high feeding rates support the conclusion that
Coleps can use dead organic matter as an additional food source.
相似文献