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onsdag 10 februari 2010

Consequences of sensory plasticity in fish

In a recent paper published in Proceedings of the Royal Society of London B (Chapman et al. 2010: http://rspb.royalsocietypublishing.org/content/early/2010/01/05/rspb.2009.2055.full.pdf+html) we report on the consequences of sensory plasticity in a species of freshwater fish, the guppy. Sensory plasticity is a widely documented phenomenon where animals compensate for sensory deprivation in one sense (e.g. vision) by an improvement in the performance of an alternative sense (e.g. smell). Surprisingly the consequences of sensory plasticity for important survival-related behaviours such as locating food have not been tested. In our experiments we show that fish that experience poor visual conditions (low light) in early life make a sensory ‘switch’ to a reliance on ‘smelling’ chemical cues to find food. These fish effectively compensate for difficulty in seeing food by this switch, and we find that fish reared under visually poor conditions will continue to rely on smell even when tested under standard light conditions. Our research suggests that this switch from vision to smell may help individuals to carry out foraging behaviour that is essential to their survival in a visually poor environment. Given that many human activities can affect the sensory environment animals experience (such as increased turbidity in lakes and ponds and acoustic noise in urban environments) the ‘compensatory plasticity’ we find in our study may provide a buffer that allows animals to carry out fundamental behaviours such as finding food in the face of substantial change to the sensory environment.

Thanks to Lesley Morrell for the guppy photo! (http://www.personal.leeds.ac.uk/~bgyljm/)


torsdag 4 februari 2010

Why do tabanids attack black horses?

In a recent paper published in Proceedings of the Royal Society of London B (Horváth et al. 2010; http://rspb.royalsocietypublishing.org/content/early/2010/01/28/rspb.2009.2202.full.html#ref-list-1) we report on why dark (black and brown) horses suffer from more attacks from blood sucking tabanids (horse flies) compared to white horses. The reason is that the dark coat of the horse reflects polarized light from the sky in a way much similar to a water surface. The blood sucking tabanids are attracted to water to drink and to lay their eggs, and use information from reflected polarized light also to locate hosts. It is the female tabanids that are attracted to the host to suck blood, and use this meal to produce eggs. Tabanid attacks can be severe and cause spreading of diseases to humans and grazing animals as well as reduce milk production in cattle. What we can learn from this is that we shall dress in white cloths and avoid dark, black clothing when in the field, especially when visiting wet areas with high numbers of tabanid flies.