The official homepage of FWF Project P 31258-B29

"Intricate bodies in the boundary layer – bridging fluid mechanics, morphology and ecology in larval Drusinae (Insecta: Trichoptera)"

 

 

 

 

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The Project Team

 

 

(from left):

Carina Zittra (University of Vienna, Dept. of Limnology & Bio-Oceanography)

Johann Waringer (University of Vienna, Dept. of Limnology & Bio-Oceanography; PI)

Hendrik Kuhlmann (Vienna University of Technology; Inst. of Fluid Mechanics & Heat Transfer; PI)

Simon Vitecek (Wassercluster Lunz, Aquatic Entomology Lab)

Ariane Neale Ramos Vieira (Vienna University of Technology, Inst. of Fluid Mechanics & Heat Transfer)

 

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Mission statement

 

 

Drusinae are restricted to high-gradient, turbulent running waters in hard-substrate channels covering the Eurasian mountain ranges from Spain to Iran. Larval heads are frequently fitted with frontal concavities, dimples, setal and lanuginose hair covers, and pronota show steep dorsal humps or high, sharp ridges. A molecular phylogeny of the subfamily yielded three well-supported clades which completely correlated the strange head and pronotum morphology with the feeding ecology of larvae: omnivorous shredders (one morphological type), epilithic grazers (three morphotypes), and carnivorous filter feeders (three morphotypes).

Data available suggest that these seven morphotypes inhabit distinct stream sections differing in hydrodynamic stress. We hypothesize that shredders are restricted to hydrodynamic low stress patches within their habitat, because their food items are concentrated near the banks. Carnivorous filter feeders are expected to be most abundant within medium to high stress patches because current velocity is required to efficiently operate their filtering apparatus. Grazer types should be generally restricted to hydrodynamic high stress patches because autotrophic biofilms and epilithic algae are most abundant near midstream. In work package 1 we will critically test this hypothesis by measuring hydraulic stress acting at the larval locations based on acoustic Doppler velocimetry; this information will be combined with video documentations of body postures and flow exposition using a waterproof endoscope camera both at the sediment surface and within substrate interstices.

In the second work package we propose that the diversification of external head capsule shapes of the seven morphotypes will impact internal head capsule structures. We hypothesize a shift in the origins of the main muscle bundles as well as innervation patterns in response to the development of frontoclypeal rims, concavities, steep frons sections and dorsal depressions. X-ray microtomography will be used to create virtual 3D models of the seven larval morphotypes to identify anatomic key innovations promoted by feeding type evolution and exploitation of hydrological niches in Drusinae.

AutoCad-based virtual 3D models provided by X-ray microtomography will be used for the numerical flow simulations intended in work package 3. This fluid-mechanical approach will allow for analyzing the effects of roughness elements on morphotype-specific hydrodynamic drag and lift forces over a wide range of Reynolds numbers and for interpreting hydrodynamic profiles obtained in the field. We hypothesize that the range of head morphologies of Drusinae larvae can be explained by the flow conditions to which the larvae are exposed. Hydraulic niche utilization combined with species-specific shear stress conditions triggered evolutionary differentiations of head and pronotum morphology, thereby optimizing lift force reduction required for the larvae to stay attached to the riverbed.