Wednesday, May 28, 2008 - 11:15 AM
405

Caddis flies as gardeners: Psychomyiid larvae recycle nitrogen and eat their own galleries

Nicola L. Ings, Alan G. Hildrew, and Jonathan Grey. School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, United Kingdom

Sedentary grazers, such as gallery-building caddis larvae of the family Psychomyiidae, must obtain sufficient food from the small area surrounding their retreats. Larval galleries have often been assumed simply to provide residents with protection, although it has also been postulated that secreted nutrients fertilize algae growing on gallery walls. This would constitute ‘gardening’ since residents obtain more and better quality food. The effectiveness and importance of this type of gardening should depend on levels of external nutrient sources, and be reduced in higher productivity systems.

Here we use stable isotopes to investigate gardening in Tinodes waeneri from the stony littoral of six lakes, spread across a nutrient gradient. δ15N and δ13C values provide information on larval diet, while δ15N values of galleries relative to epilithic biofilm indicate the degree of nitrogen recycling within the gallery community.

Our results demonstrate that larvae do eat their galleries and nitrogen is recycled within the gallery community. These data provide evidence that T. waeneri galleries do act as a garden and that nutrient recycling within the gallery community could sustain productivity at times when external nutrient concentrations are low. This has potential implications for community structure and ecosystem function within the littoral of lakes.



Web Page: gardening, littoral, stable isotopes

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