The ethograms of Uronychia transfuga and Uronychia setigera (Ciliata, Hypotrichida): a comparative approach for new insights into the behaviour of protozoa

The behavioural biology of Uronychia transfuga and Uronychia setigera was s tudied and their complete ethograms (namely the catalogues of both the qual itative elements and the relative quantitative parameters of locomotion) we re drawn. Several other points of biological relevance emerged: (a) the two hypotrichs proved to have evolved only a partial substrate dependence, the ir adaptive strategy relies on a very weak grip on the substrate; (b) U. tr ansfuga and U. setigera (they share the same basic body shape, while differ ing in body length, 118 and 64 mu m, respectively), creep on the substrate following patterns quantitatively different in terms of their absolute valu es (e.g. velocity: U. transfuga similar to 300 pm/S; U setigera similar to 150 mu m/s). When the ratio between the same values and the species-specifi c body size is made (namely when the measurements are expressed in Relative Units, R.U.), they become quite similar to each other; this demonstrates t hat creeping of these two species is size-dependent; (c) the swimming of bo th species occurs only backwards and at incredibly high velocities (U. tran sfuga: (v) over right arrow = 6,302 mu m/s, approximate to 54 RU/s; U. seti gera: (v) over right arrow = 7,347 mu m/s, approximate to 115 RU/s); (d) bo th species show clear-cut rheo-responses and photo-responses, that is, they are capable of reacting to water currents and to sudden increases of light . Double organisms of U. setigera do not creep, but swim forewards only irr egularly and backwards along straight paths at high velocity (similar to 3, 700 mu m/s).