| Hydra sp., located at the roots of a willow tree in lotic water. (1) |
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| Hydra sp., tentacle with cnidocysts |
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| Hydra sp.; part of a tentacle with cnidocysts. Glu: glutinant; Vo: volvent; Pe: penetrant. The arrows point to some of the cnidocils of the penetrants.(2) |
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| Hydra sp.; discharged penetrants (2) |
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| Hydra sp., discharged volvents |
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| Hydra sp., discharged glutinant |
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| This nematode came too close to the Hydra (4.3.2007) |
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| Nematode with penetrants (4.3.2007) |
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| Hydra sp., is very often infested by a ciliate: Trichodina pediculus |
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| Trichodina pediculus, an ectoparasite of Hydra |
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| Location: Gevelsberg, Stefansbach (1); Nature reserve NSG Heiliges Meer, NRW, Germany, pond: Kleinweiher "Üffings Wiese" (location 16) (2); |
| Habitat: root of willow tree (Salix sp) (1); plankton with detritus/ algae (2) |
| Date: 23.06.2006 (1); 16.11.2021 (2) |
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