Does the lateral bundle of the medial olfactory tract mediate reproductive behavior in male crucian carp?

The olfactory tract in crucian carp (Carassius carassius) is divided into three distinct bundles: the lateral tract (LOT) and the lateral (lMOT) and medial (mMOT) bundles of the medial tract. The LOT has been shown to mediate information associated with feeding behavior, whereas the mMOT mediates information associated with alarm response. The role of the medial olfactory tract (lMOT and mMOT) in reproductive behavior is still under debate. In the present experiment, male reproductive behavior towards prostaglandin-injected females was investigated before and after cutting off the different olfactory tract bundles, to determine which of the tract bundles is essential for mediating reproductive behavior in male crucian carp. The fish were maintained in physiological saline before and after surgery to preserve the remaining tract bundles. Operations were performed symmetrically on both sides and post-operative inspections revealed the functionality of the intact tracts. Sham-operated males and males with only the lMOT intact showed typical reproductive behavior, with following of the female and inspections of the female anal papilla. However, males in which the lMOT was cut, leaving both the mMOT and the LOT intact, showed reduced reproductive behavior. Our results suggest that the lMOT mediates reproductive behavior in male crucian carp.