Getting into hot water: sick guppies frequent warmer thermal conditions

Abstract

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.

Temperature Preference and Sex Differentiation in African Catfish, Clarias gariepinus

“…Indeed, in Zebrafish, stressed individuals spent more time at higher temperatures in continuous thermal system and then showed an emotional fever (Rey et al., ). In the Nile tilapia (Cerqueira et al., ) and the Trinidadian guppy (Mohammed et al., ), bacterial infection induced behavioral fever. Infected individuals spent more time at higher temperature in continuous thermal gradient system to reduce bacterial load.…”

Behavioral fever in ectothermic vertebrates

“…1b) including LPS (Cabanac and Laberge, 1998;do Amaral et al, 2002;Grans et al, 2012;Merchant et al, 2007Merchant et al, , 2008Reynolds et al, 1978;Sherman et al, 1991), various species of Gram-positive and Gram-negative bacteria, administrated as killed or live forms (Bernheim and Kluger, 1976a,b;Burns et al, 1996;Casterlin and Reynolds, 1977;Covert and Reynolds, 1977;Hallman et al, 1990;Kluger, 1977;Kluger et al, 1975;Monagas and Gatten, 1983;Muchlinski et al, 1995;Myhre et al, 1977;Ortega et al, 1991;Ramos et al, 1993;Reynolds, 1977;Reynolds et al, 1976Reynolds et al, , 1978Vaughn et al, 1974), fungi (Murphy et al, 2011;Richards-Zawacki, 2010), ectoparasite (Gyrodactylus turnbulli) (Mohammed et al, 2016), synthetic dsRNA (poly I:C) (Boltaña et al, 2013) or viruses (Boltaña et al, 2013). Because of the relatively low sensitivity of fish and toads to LPS, the dose used to induce behavioral fever in these animals (toad:…”

Alpine bullhead (Cottus poecilopus Heckel): a potential refuge for Gyrodactylus salaris Malmberg, 1957 (Monogenea)

“…The maximum average life span of individual G. salaris when feeding on its natural salmon host, or indeed when detached from a host, is negatively correlated with water temperature (Olstad et al 2006). Environmental temperature not only impacts survival but also affects most other gyrodactylid functions (e.g., Gelnar 1991, Mohammed et al 2016 and in the host both the alternative and classical complement pathway activities can be depressed during cold periods (Hayman et al 1992, Collazos et al 1994, Harris et al 1998. In northern parts of Norway, river temperature is around 0 o C during winter (see The Norwegian Water Resources and Energy: Directorate; https://www2.nve.no/h/hd/plotreal/WT/index.html).…”