Comparing macrophyte herbivory by introduced Louisiana crayfish (Procambarus clarkii) (Crustacea: Cambaridae) and native Dytiscid beetles (Cybister tripunctatus) (Coleoptera: Dytiscidae), in Kenya

  • Sadie K Rosenthal Department of Biological Sciences, University of Notre Dame, PO Box 369, Notre Dame, Indiana 46556, USA
  • David M Lodge Department of Biological Sciences, University of Notre Dame, PO Box 369, Notre Dame, Indiana 46556, USA
  • Kenneth M Mavuti Department of Zoology, University of Nairobi, PO Box 30197, Nairobi, Kenya
  • Wairimu Muohi Department of Zoology, University of Nairobi, PO Box 30197, Nairobi, Kenya
  • Philip Ochieng Department of Zoology, University of Nairobi, PO Box 30197, Nairobi, Kenya
  • Benjamin N Mungai Center for Biotechnology Research and Development, Kenya Medical Research Institute, PO Box 54840-00200 City Square, Nairobi, Kenya
  • Gerald M Mkoji Center for Biotechnology Research and Development, Kenya Medical Research Institute, PO Box 54840-00200 City Square, Nairobi, Kenya
Keywords: carbofuran, Dytiscidae, Furadan, non-target species, Oryza sativa, preference, rice

Abstract

The omnivorous Louisiana crayfish, Procambarus clarkii, has caused significant changes to macrophyte communities worldwide and may have similar negative effects in Kenya if used as a biological control agent for snails harbouring human schistosomes. Here we examine how herbivory by the introduced Louisiana crayfish might change macrophyte abundance and species composition relative to herbivory by a prevalent native beetle Cybister tripunctatus. Our observations are thought to be the first on the consumption of live macrophytes by adult dytiscid beetles, which are commonly known as predaceous diving beetles. In a laboratory experiment, we compare herbivory rates and macrophyte species-selectivity between the beetle and the crayfish. Combining the herbivory rates with population estimates of crayfish and beetles in a local pond, we estimate that herbivory in the natural environment is of the same order of magnitude. Preferences among macrophyte species are also similar between herbivores, except that crayfish are likely to have a larger impact than beetles on cultivated rice (Oryza sativa). Results from a laboratory toxicity experiment suggest that the crayfish is not currently a rice pest in Kenya because it is killed by Furadan® 5G, the commonly applied pesticide.

Keywords: carbofuran, Dytiscidae, Furadan, non-target species, Oryza sativa, preference, rice

African Journal of Aquatic Science 2005, 30(2): 157–162
Published
2006-01-04
Section
Articles

Journal Identifiers


eISSN: 1727-9364
print ISSN: 1608-5914