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Non conventional animal models: The Gerromorphes

What are they?

Gerromorphs are semi-aquatic bugs that are incorrectly called "water spiders" or "skaters" because of their long legs. They are Hemipterans, Heteroptera.

This group of predatory insects comprises about 2000 species found on all continents, living on the surface of water in a wide variety of habitats: ponds, rivers and even oceans. Gerromorph species also have diverse morphologies, particularly with regard to the shape and size of their legs. The life cycle is divided into several stages: after hatching from the egg, the nymph grows through 5 successive moults until it reaches its adult size.

Why use these insects in research?

The extraordinary ability of Gerromorphs to walk on water has led to a great deal of research into this mode of locomotion. In addition, studies have attributed the diversity of this group of insects to environmental factors such as male/female and predator/prey interactions. These elements therefore lead to making Gerromorphs model organisms in ethology and ecology for the study of biodiversity.

The adaptation to life on the water surface involves an elongation of the legs, as well as an increase in their hairiness, which makes the ends of the limbs impermeable. These evolutionary transformations can be explained by mutations in certain genes that have modified the development and growth of the legs of these insects.

Thus, the richness of biodiversity in water bugs provides a good model for identifying the genes and genetic changes responsible for morphological changes during evolution (evo-devo).

What for?

At the IGFL, we use Gerromorphs to :

  • Identify the genes responsible for the morphological evolution of water bugs (e.g. leg elongation that allowed colonisation of the water surface).
  • Understand how these genes function.
  • To explain the molecular mechanisms behind biodiversity.

For more information:

Integrating evo-devo with ecology for a better understanding of phenotypic evolution. M. E Santos, C. S Berger, P. N Refki, and A. Khila (2015). Brief Funct Genomics, 14(6):384-95.