Abstract
Guppies have successfully established populations in places with thermal regimes very different from the Tropical conditions in their native range. This indicates a remarkable capacity for thermal adaptation. Given their vulnerability to predation as juveniles, acute changes in temperature, which can alter predator-prey relationships, can impact juvenile survival and have amplified consequences at the population level. To understand how temperature may impact juvenile survival and gain insight into their success as an invasive species, we researched the effect of acute temperature changes on the routine swimming behaviour of juvenile guppies. Using a novel 3-dimensional tracking technique, we calculated 4 routine swimming parameters, speed, depth, and variation in speed or depth, at 6 different test temperatures (17, 20, 23, 26, 29, or 32°C). These temperatures cover their natural thermal range and also extended past it in order to include upper and lower thermal limits. Using model selection, we found that body length and temperature had a significant positive relationship with speed. Variation in speed decreased with rising temperatures and fish swam slightly closer to the bottom at higher temperatures. All juveniles increased variation in depth at higher temperatures, though larger individuals maintained slightly more consistent depths. Our results indicate that guppies have a large thermal range and show substantial plasticity in routine swimming behaviours, which may account for their success as an invasive species.
Highlights
Temperature can affect every aspect of the physiology and performance of organisms (Johnston and Bennett, 2008; Angilletta, 2009)
The results of this study indicate that changes in water temperature, even over a short period of time, can affect the routine swimming activity of juvenile guppies
The effect of temperature on variation in depth was found to vary with length, where larger individuals swam slightly shallower than smaller individuals and maintained more consistent depths
Summary
Temperature can affect every aspect of the physiology and performance of organisms (Johnston and Bennett, 2008; Angilletta, 2009). Temperature can affect muscle fibre number (Wilkes et al, 2001) and muscle performance (Putnam and Bennett, 1982), endurance (Ojanguren and Branta, 2000), growth (Angilletta et al, 2004), metabolic rate (Das and Das, 1982), heart rate (Richards, 1963), immune. Temperature can elicit thermoregulatory and avoidance behaviours such as altered distribution patterns (Walther et al, 2002), microhabitat use (Taylor, 1988; Adolph, 1990), foraging tactics (Persson, 1986; Fraser et al, 1993; Ayers and Shine, 1997), and courtship behaviours (Hilder and Pankhurst, 2003; Denoel et al, 2005)
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