Alarm Reaction in the Crucian Carp is Mediated by the Medial Bundle of the Medial Olfactory Tract

摘要

Experiments were performed to determine which bundles of the ohfacor. :~a’c~ .~re e~er: a: ? r-e: a: ~‘g alarm reaction in crucian carp (Carassius carassius L.). The fish were maintained in ~r>’scIogIica sa~i~re e~er s.~:er, cc preserve the remaining tracts and postoperative inspections revealed the functionality of the niact r~c~ C,era:i:’~’s :r tre tracts were performed symmetrically on both sides. Sham-operated and non-operate’c sh sno~.’~ec er ~c.a aia~m cena~iour of fast swimming to the bottom, dashing movements and aggregation when exposec cc s~n e~’~ct a C” c:r:a n alarm substance. Fish with only the medial bundle of the medial olfactory tract ntact also displayed ~he al~ir~ oe.r.a, :~r con exposure; however, these fish did not react to the amino acid, L-alanine with either feeding rcn~’~’ a~r’rn reacc,:n ....r.cian carp which had the medial bundle of the medial olfactory tract cut, leaving both the lateral cund~ o~fthie e~ a :lfactory tract and the lateral olfactory tract intact, did not display any alarm reaction to skin e>crac:; ~ dr~fsh ~eaC&J to exposure to L-alanine with feeding behaviour. There were statistically significant differen ~ ~ d~ie b&a. o~ srores for the fish subject to different treatments. The present study demonstrates that the media b~nd~ofd~ meoi.a oltactory tract appears to be both necessary and sufficient for mediation of the alarm reaction. The r~Ii~ ahso ~ ~at the sensory neurons which respond to alarm substance terminate and make synaptic connections ~~mn the 5&.ondan~ ne~~.rons that make up the medial bundle of the medial olfactory tract; thereby demonstrating the specrlhcity ‘of ~ie s~bai aspect of olfactory processing. The results are discussed with respect to the spatial aspect of organization w~1tthunn the ofaccory system, the pattern of generalization across orders of fish, and the functional implications of toe spatial arirar~emen: cf nformation transmission between the peripheral olfactory organ and the brain.