Developmental biomechanics of axial muscle structure and activity patterns in larval zebrafish.

Larval fish have to swim effectively to evade predators and catch prey, while they undergo major e, as well as in muscle fibre morphology and arrangement. It is unclear how fish larvae coordinate their muscles to generate these swimming movements. To tackle this question, we will measure muscle architecture and spatiotemporal activation patterns in zebrafish larvae (Danio rerio) aged 2–12 days. Muscle fibre arrangements will be quantified in 3D using high-resolution scans (microCT and laser-sheet microscopy). To measure muscle activation, we will stain the muscles with a voltage-sensitive fluorescent dye. With two high-speed cameras, we will capture both the activity specific modulation of fluorescence using a high-resolution image intensifier and the fish’s body curvature. Together, these data will allow us to test (1) whether the changing muscle fibre orientations during development minimize variations in muscle strain within transversal sections along the body and (2) whether the activation waves run much faster along the body than the curvature wave (hypothesis based on previous predictions of bending moments, or net muscle actuations, along the body from kinematic observations). Furthermore, we will test how muscle strains vary along the entire trunk because the functional requirements differ along the trunk of the fish. Our approach is a crucial step towards understanding optimization of fish locomotion during development. The data are also essential input for future forward-dynamics models that predict swimming motions from muscle activations.