How to get a sleeker body in four weeks

Posted on September 26, 2009

Some animals respond to different environmental conditions by changing their body form.  Compared to control fish raised in still water, juvenile montezumae swordtails (Xiphophorus montezumae) raised in flowing water for 32 days developed more streamlined bodies by increasing their length : depth ratio.  In faster-swimming fish species such as salmonids, forced exercise is known to increase food intake, which provides the energy needed for swimming.  In contrast, the swordtails in these experiments didn’t show a similar change in appetite.  These results point to the possibility that fast- and slow-swimming species may respond differently to high flow conditions, and that species with changeable body form can reduce their energy needs through better streamlining. 

Reference:    Alcaraz, G. & Urrutia, V.  2008.  Growth in response to sustained swimming in young montezumae swordtails, Xiphophorus montezumae.  Marine and Freshwater Behaviour and Physiology  41(1), 65–72.