The air-water interface: A microhabitat for hypotrichous settlers (Protista, Ciliata)

Abstract

The spatial distribution of Oxytricha bifaria (a hypotrich ciliate) was studied in the laboratory to gain information about a poorly known habitat—the air‐water interface. The results show that this species settles on the interface whenever a bacterial film grows. The ciliate’s locomotory behavior is restricted on newly colonized interfaces but returns to normal patterns on solid substrata when a complete bacterial film develops on the interface. When the bacterial film is broken, ciliate motion is restricted to the micro‐“floes” of bacteria, thus inducing a patchy distribution on the ciliates. Field observations confirm laboratory results. Behavior‐induced patterns in microhabitat distribution may have effects on the reproductive biology of these protozoa.

<b>REGULAR ARTICLES / ARTICLES RÉGULIERS</b><p>Movement of the cirri during the creeping of <i>Euplotes crassus</i> (Ciliata, Hypotrichida)

“…Contrary to what was reported by Machemer and Deitmer (1987) and Sugino and Machemer (1990), the occurrence of the ZP and the repositioning process leading to it point to the importance of such contact between the cirrus and the substrate. Our findings agree with the evidence discussed in the studies of the behaviour of Oxytricha bifaria creeping on rough substrates (Ricci et al 1989) and moving underneath the water-air interface on a bacterial film (Ricci et al 1991). Such a feedback interaction between the tip of the cirrus and the substrate might be mediated (at least in part) by the adhesion processes occurring during the tipsubstrate contact.…”

“…This exclusive characteristic of the hypotrichs, expressed by their wellknown thigmotactism, has been investigated from many different perspectives in our laboratory (Ricci 1989a(Ricci , 1989bRicci et al 1989Ricci et al , 1991.…”

Locomotion and feeding of Acanthamoeba at the water–air interface of ponds

“…Furthermore, passive drift will tend to concentrate bio¢lm material into slicks which further accentuate the possibilities for grazing. Interestingly, Hypotrich ciliates, which themselves exploit the surface bio¢lm, modify their motile behaviour to maximise their chances of exploiting these rich islands of potential food [2].…”

Locomotion and feeding ofAcanthamoebaat the water–air interface of ponds

“…Furthermore, passive drift will tend to concentrate biofilm material into slicks which further accentuate the possibilities for grazing. Interestingly, Hypotrich ciliates, which themselves exploit the surface biofilm, modify their motile behaviour to maximise their chances of exploiting these rich islands of potential food [2].…”

“…Ricci et al [2] have shown that the water–air interface allows the specialised substratum‐dependent creeping locomotion of Hypotrich ciliates whose motile behaviour maximises foraging for abundant bacteria. Our preliminary investigations on a number of freshwater ponds showed amoebae to be common in surface microlayer samples.…”