Getting into hot water:sick guppies frequent warmer thermal conditions

Ectotherms depend on the environmental temperature for thermoregulation and exploit thermal regimes that optimise physiological functioning. They may also frequent warmer conditions to up-regulate their immune response against parasite infection and/or impede parasite development. This adaptive response, known as ‘behavioural fever’, has been documented in various taxa including insects, reptiles and fish, but only in response to endoparasite infections. Here, a choice chamber experiment was used to investigate the thermal preferences of a tropical freshwater fish, the Trinidadian guppy (Poecilia reticulata), when infected with a common helminth ectoparasite Gyrodactylus turnbulli, in female-only and mixed-sex shoals. The temperature tolerance of G. turnbulli was also investigated by monitoring parasite population trajectories on guppies maintained at a continuous 18, 24 or 32 °C. Regardless of shoal composition, infected fish frequented the 32 °C choice chamber more often than when uninfected, significantly increasing their mean temperature preference. Parasites maintained continuously at 32 °C decreased to extinction within 3 days, whereas mean parasite abundance increased on hosts incubated at 18 and 24 °C. We show for the first time that gyrodactylid-infected fish have a preference for warmer waters and speculate that sick fish exploit the upper thermal tolerances of their parasites to self medicate

‘Civilizing’ the pastoral frontier: land grabbing, dispossession and coercive agrarian development in Ethiopia

This paper analyzes frontier dynamics of land dispossessions in Ethiopia’s pastoral lowland regions. Through a case study of two sedentarization schemes in South Omo Valley, we illustrate how politics of coercive sedentarization are legitimated in the ‘civilizing’ impetus of ‘improvement schemes’ for ‘backward’ pastoralists. We study sedentarization schemes that are implemented to evict pastoralist communities from grazing land to be appropriated by corporate investors. It is argued that frontier imaginations of pastoral lowlands legitimate coercive practices of ‘emptying’ the lowlands for investments. ‘Improvement schemes’ enroll private investors and enterprises affiliated with Ethiopia’s ruling party in the politics of ‘thickening’ state presence in the pastoral frontier. Agricultural extension packages serve to expand state control over sedentarized pastoralists and make lowland resources more extractable, for investors and for the ruling regime