THE CROWDING EFFECT - AN ETHOLOGIC ANALYSIS

Authors
Citation
N. Ricci et F. Erra, THE CROWDING EFFECT - AN ETHOLOGIC ANALYSIS, European journal of protistology, 31(3), 1995, pp. 302-308
Citations number
25
Categorie Soggetti
Microbiology
ISSN journal
09324739
Volume
31
Issue
3
Year of publication
1995
Pages
302 - 308
Database
ISI
SICI code
0932-4739(1995)31:3<302:TCE-AE>2.0.ZU;2-G
Abstract
The phenomenon of crowding of ciliates in rest areas has been describe d previously [23]: these organisms tend to collect on the bottom of an experimental apparatus under objects interfering with the water-air i nterface. The behaviour of Oxytricha bifaria has been analyzed as a ba sic element possibly accounting for the effect itself: to monitor the phenomenon properly a well-defined time (1 h 15 min) was chosen during the formation of the overcrowded population; in addition, well-define d areas were TV recorded, the populations within them studied and thei r behaviour analyzed and compared. The results obtained are the follow ing: (a) the number of idle cells is significantly larger in the Shelt er-Area (S) than in the Open (O); (b) there is a net inward flow of ox ytrichas, constantly enhancing the cell density in S; (c) the ethogram of oxytrichas creeping into S is quite similar to that of the populat ions in O: only the creeping velocity in S is smaller than in O; (d) t he frequency of Side Stepping Reactions performed by O. bifaria at the level of the border between S and O is 5-6 times higher for oxytricha s creeping outwards than for those entering S. The combined effect of these phenomena well accounts for the formation of the crowding condit ions.