fne[KOZ2] mutants are viable, but exhibit a specific and fully penetrant fusion of the β-lobes in their mushroom bodies. Mutant males display reduced courtship indices, but normal short- and long-term courtship memory.

5-day old naive fne^KOZ2 mutant males initiate wing display to females, as in wild-type flies. However, a fraction of the fne^KOZ2 males do not attempt any copulation (22% with a virgin female, 33% with a fertilized female), a rare event when observing wild-type male behavior. In addition, fne^KOZ2 males copulate with a virgin female with an average latency of 345 seconds, compared to 192 for wild-type males. Thus, fne^KOZ2 mutants are able to perform all the steps of courtship behavior but progress through these steps less actively than wild-type males.

Average wing extension onset is not significantly different between fne^KOZ2 and wild-type males. However, only two-thirds of fne^KOZ2 males attempt copulation during a 10 minute period, as oppose to 100% of wild-type males. In addition, the onset of the copulation attempts us delayed in fne^KOZ2 males. Further, the average number of copulation attempts is reduced in fne^KOZ2 males compared to wild-type. Finally, the average copulation index of wild-type males is 56.5% compared to 28.5% in fne^KOZ2 males. These data show that although the onset of wing extension following the male and female encounter are similar in wild-type and fne^KOZ2 males, the intensity of courtship is significantly reduced in fne^KOZ2 males.

There is no significant difference between naive and trained fne^KOZ2 males with respect to the fraction of males attempting copulation and to the onset of copulation attempts (both short-term and long-term memory). Trained wild-type males attempt fewer copulations than naive males, unlike fne^KOZ2 males whose level of copulation attempt is uniformly low. The most significant differences between naive and trained males is for the copulation index values that decrease after training. fne^KOZ2 mutants significantly learn and remember in the paradigms of short-term memory and long-term courtship retraining sets.

In a small fraction of fne^KOZ2 brains, there is an apparent fusion of the medially projecting lobes of the mushroom body (β lobes) at the midline, both in males and in females. The majority of the fne^KOZ2 brains are indistinguishable from hemizygous males or from heterozygous fne^KOZ2/+ female brains, with β axon fibers terminating near the midline without crossing it. No other alterations in the mushroom body loves, specifically α, β and γ are detected. The ellipsoid body, one of the four neuropils of the central complex, is maintained in fne^KOZ2 mutants.

fne^KOZ2/Df(1)fne^Δ, Rbp9^P2690/Df(2L)ED206 has short lived phenotype