The sea lamprey, Petromyzon marinus, exhibits a spectacular
alarm response to the odor emitted from decayed conspecifics that may differ
substantially in function from the well-characterized system in ostariophysan
fishes. Here, we report a series of three laboratory experiments designed to
characterize the behavioral responses of migratory-phase lampreys to a set of
odors derived from conspecific and heterospecific tissues, determine whether sex
or sexual maturation alters these responses, and ascertain if the putative alarm
substance derives from a particular region of the body. A number of the
findings were consistent with the prevailing predator-avoidance paradigm for
fish alarm substances released from the skin after predator attack in that:
(1) dilute odors derived from freshly ground skin were highly repellent;
(2) the substance is contained in the organism early in life;
(3) the odor derived from a close relative was avoided whereas those of a
distant relative were not; and (4) upon sexual maturity female response
to the alarm substance was attenuated. Two interesting patterns arose that
differed substantially from the prevailing paradigm: (1) conspecific
odors remained repellent after 96 h of aerobic decay; and (2) the
cue was emitted from multiple areas of the body, not just the skin, and the
repellency of the odor derived from any tissue increased in accordance with its
mass. A persistent cue emitted from several sources suggests a broader
ecological function than the detection and avoidance of a predator.
Alarm substance induced behavioral responses in zebrafish (Danio rerio)
