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Biomedical subjects

N Ricci

Publications and source records attributed to N Ricci.

48 records · Page 3Linked to original sources
PubMedDate not supplied

The interface between air and water: a perturbation source eliciting adaptive behaviour in ciliates.

Interference with the water-air interface, both direct (by contact with a flat, rigid surface) and indirect (by inducing a meniscus) caused the ciliated protozoa we investigated to actively collect in the water column or on the substrate directly under the area of altered surface tension. A crowding effect is observed in this "rest area" reaching plateau values within one hour after onset of the experiment. The simple experimental procedures described here induced analogous behaviour in both Paramecium caudatum (a swimmer) and Oxytricha bifaria (a crawler). The ciliates seem in this reaction to be seeking a refuge from vibrations transmitted by the free interface. Our discovery is discussed in its implications for the adaptive biology and ecology of these micro-organisms.

Air↗
PubMedDate not supplied

The behavior of the doublet of Oxytricha bifaria (Ciliata, Hypotrichida): a contribution to the understanding of this enigmatic form.

The tracks of normal organisms of Oxytricha bifaria and of stage IA, IB, II, III, IV and V doublets were studied to test the hypothesis that the doublet might function as a dispersal form. Stage IA, the only stage to swim, swims straight with only rare interruptions; its rate of mobility (Rmo = 443 micro/s) is roughly twice that of singlets (Rmo = 218 micro/s). Stage IA doublets swim in three-dimensional movement which enables them to be carried away by water currents. The other stages seem to represent passage back towards the normal singlet form. The ethological evidence reported here together with other results already published supports the working hypothesis that the doublet of O. bifaria is a dispersal form suggests that the doublet might well represent a special fourth differentiation state of this species in addition to pairs, giants, and cysts.

Animals↗
PubMedDate not supplied

Cold microgradients elicit adaptive behavior in isotropically cooled, inert populations of Oxytricha bifaria (Ciliophora, Hypotrichida).

To complete our investigations on the oriented behavioral response of isotropically cooled, inert populations of Oxytricha bifaria to a warm thermal gradient, their physiological potentialities under cold microgradient conditions arising at 8.5 degrees C were studied. We monitored the behavior of the experimental populations, both at the level of the passing cold wave front, and afterwards when the thermal gradient stabilized, evaluating (i) their distribution in general, (ii) their relative centroids, (iii) the percentage of both backward creeping and immobile ciliates, and (iv) the numerical indices and rates of their creeping tracks. At the arrival of the cold wave front, the oxytrichas react immediately to the thermal stimulus, creep backwards at very high velocity along uninterrupted linear tracks, and thus move away from the cooling source. No specific behavioral response was ever observed in the static microgradient conditions. At 8.5 degrees C, despite their inertness, the ciliates are still able to behave adaptively, reacting immediately and orientatedly, once a directional factor (the cold-repelling thermal gradient) arises in an isotropic environment. This is similar to their behavior in the symmetric warm attracting thermal gradient.

Adaptation, Physiological↗