Behavior of single- and mixed-sex infections of Nippostrongylus brasiliensis in fed and fasted mice.

The behavior of male and female Nippostrongylus brasiliensis differed in the intestines of mice. Intraintestinal insertion of female worms at sites that represented 5 or 20% of the pyloric-caecal distance revealed localization at those sites, whereas male populations dispersed over 50% of the intestinal length. However, introduction of females at 40% of the intestine showed a wider distribution that was similar to the male's behavior at all three locations in the intestine. Insertions of both sexes reduced the male's dispersal behavior and arrested the female's preferential localization at the 5 and 20% intestinal sites. Females that were posterior in the intestine showed no dose-dependent movement toward males that were more anterior over various distances or with various combinations of ages of males and females. Food deprivation altered the behavior of females, but this change was inhibited, apparently by males, in bisexual groups. Dispersal of bisexual populations in the intestine was independent of helminth density after fasting of the host.