Anomalous diffusion analysis reveals cooperative locomotion of adult parasitic nematodes in sex-mixed groups.
Parasitic worms are widespread throughout the world and causing agents of chronic infections in humans and animals. The majority of these pathogens parasitize the gut of the infected hosts, however very little is known about the locomotion of the worms dwelling the gut. We studied the movement of Heligmosomoides bakeri (previously Heligmosomoides polygyrus), a natural infection of mice and usually used as animal model to study the roundworm infections. We investigated the locomotion of H. bakeri in simplified environments mimicking key physical features of the intestinal lumen, i.e. various medium viscosities, and a periodical intestinal villi topography. The non-periodical nematode motion in these settings could be described by anomalous diffusion theory. Fascinatingly, an oriented, super-diffusive locomotion of nematodes in sex-mixed groups were detected, in the sense of a cooperative, but not collective (swarm-like) migration stimulated by mating and reproduction, while individual nematodes moved randomly, following a diffusive motion regime. High mucus-like medium viscosity and villi topography, representing physical constraints of nematode locomotion, slowed down but did not prevent this cooperative migration. Additionally, the mean displacement rate of nematodes in sex-mixed groups of 6{middle dot}10-4 mm/s in viscous mucus-like medium are in good agreement with estimates of nematode migration velocities between 10-4 to 10-3 mm/s in the gut. Thus, our data indicate the intestinal nematodes motion to be non-periodic and random but triggered to be oriented by kin of the different sex.