CSZ Student Research Grant Winner: Chloe Berger

Schistocephalus solidus: a manipulative parasite?

Characterization of worm secretions for a better understanding of their impacts on the fish host behaviour.

At the beginning of 2018, I was honoured to receive the student research grant of the Canadian Society of Zoologists. This grant helped me to realize a 4-month internship at the University of British Columbia, Vancouver, in the laboratory of Leonard Foster. During my PdD researches in the laboratory of Nadia Aubin-Horth, I am interested in the molecular cross-talk between the threespine stickleback, a small fish widely found in the Northern hemisphere, and its parasite Schistocephalus solidus, a cestode that is found inside the abdominal cavity of the fish. Sticklebacks that are infected by S. solidus show drastic changes in behaviours, which eventually lead to a loss of adaptive anti-predator behaviours. For example, sticklebacks under normal conditions perform vertical migrations in the water column so that they reach the water surface only during the night to avoid avian predators. If a fish is caught at the surface during the day, it has more probability to be infected by S. solidus. This suggests that the worm may manipulate the behaviour of the fish in order to facilitate its transmission to its bird final host. However, very little information is currently available concerning the molecular mechanisms involved in the behavioural changes of infected sticklebacks. A better understanding of these mechanisms will help to determine how these behavioural modifications evolve in nature. In this context, my internship at the University of British Columbia had two main objectives : 1) the characterization by mass spectrometry of the proteins secreted by the worm. The main hypothesis is that the worm may secrete some proteins involved in the behavioural changes of the infected fish. These proteins could be promising targets to try to « cure » the behavioural modifications of infected sticklebacks. 2) the characterization by mass spectrometry of the worm proteome (that is to say all the proteins expressed in the worm tissues), and its comparison to the secretions. The first part of my internship allowed me to develop and optimize a protocol to describe the proteins from the worm and its secretions. During the second part of my internship, I applied this protocol on five worms and their respective secretions. The results, which are currently being analyzed, will help us to better understand if the worm is able to produce « manipulative » proteins that will impact the fish behaviour. I thank the CSZ for supporting my internship that was highly beneficial for my PhD!