Observations on the Bionomics of the Freshwater Nematode Chromadorina bioculata

The biology and morphology of Chromadorina bioculata is presented. Tile nematode was abundant on the alga Cladophora of one lily pond, but absent from similar habitats in nearby ponds. The setae, caudal glands, high Iocomotory rates and positive photo response have been interpreted in relation to maintenance on, amongst and between algal filaments, suspended over large volumes of water.When placed in tap or distilled water, C. bioculata became inactive and died. The influence of pH buffers, tonicity, temperature and starvation on activity were investigated. C. bioculata survived longer in artificial sea water diluted 10 or 100 times with distilled water, or in NaCl isotonic with sea water diluted 100 or 1000 times, than in tap or distilled water. No evidence of wide osmotic toleration or osmoregulation was observed. Activity was influenced by temperature, with peak activities occurring at the seasonal normal temperature. These findings are discussed in terms of general hematology and habitat selection.