sentences:  When infected with "P. laevis", "G. pulex" become strongly photophilic and seek out light which increases their chance of predation in turn increasing the likelihood of parasite transmission.This alteration in behavior pertaining to light was found to involve an alteration in serotonergic activity of the brain.The immunoreactivity of the brain to serotonin was found to be increased by around 40 percent for infected "G. pulex" when compared to uninfected "G. pulex".