Long descending commissural V0v neurons ensure coordinated swimming movements along the body axis in larval zebrafish

Developmental maturation occurs in slow swimming behavior in larval zebrafish; older larvae acquire the ability to perform slow swimming while keeping their head stable in the yaw dimension. A class of long-distance descending commissural excitatory V0v neurons, called MCoD neurons, are known to develop in a later phase of neurogenesis, and participate in slow swimming in older larvae. We hypothesized that these MCoD neurons play a role in coordinating the activities of trunk muscles in the diagonal dimension (e.g., the rostral left and the caudal right) to produce the S-shaped swimming form that contributes to the stability of the head. Here, we show that MCoD neurons do indeed play this role. In larvae in which MCoD neurons were laser-ablated, the swimming body form often adopted a one-sided (C-shaped) bend with reduced appearance of the normal S-shaped bend. With this change in swimming form, the MCoD-ablated larvae exhibited a greater degree of head yaw displacement during slow swimming. In mice, the long-distance descending commissural V0v neurons have been implicated in diagonal interlimb coordination during walking. Together with this, our study suggests that the long-distance descending commissural V0v neurons form an evolutionarily conserved pathway in the spinal locomotor circuits that coordinates the movements of the diagonal body/limb muscles.

Automated summary

Developmental maturation in larval zebrafish is associated with slow swimming behavior, particularly in older larvae who can maintain head stability during slow swimming. The MCoD neurons play a role in coordinating trunk muscle activities to produce the stable head and S-shaped swimming form. The ablation of MCoD neurons results in a change in swimming form and increased yaw displacement of the head.