Bd. Wisenden et Mc. Millard, Aquatic flatworms use chemical cues from injured conspecifics to assess predation risk and to associate risk with novel cues, ANIM BEHAV, 62, 2001, pp. 761-766
A growing number of aquatic organisms have been shown to display antipredat
or behaviour in response to injury-released chemical cues from conspecifics
. Here, we demonstrate a clear antipredator response in the form of avoidan
ce behaviour by a free-living flatworm Dugesia dorotocephala to chemical cu
es from injured conspecifics. This is the first demonstration of a chemical
alarm cue in a platyhelminth. In a second experiment, we exposed planaria
to combined cues of sunfish odour and planaria alarm cue, or sunfish odour
alone. Planaria avoided the sunfish+alarm cue but did not avoid the sunfish
odour, indicating no prior aversion to sunfish odour. When these same plan
aria were subsequently retested 2 days later with sunfish odour only, plana
ria that had previously received sunfish odour+alarm cue avoided the cue bu
t planaria that had previously received sunfish odour alone did not. These
data indicate that planaria learned to recognize sunfish odour as an indica
tor of danger based on a single simultaneous exposure to conspecific alarm
cue and the novel cue. This is the first demonstration of this phenomenon i
n a platyhelminth and the simplest nervous system known to be capable of le
arned risk association. (C) 2001 The Association for the Study of Animal Be
haviour.