Time-lapse analysis of primordium migration during the development of the fish lateral line

The lateral line is a mechanosensory system that comprises a set of discrete sense organs called neuromasts, which are arranged in reproducible patterns on the surface of fish and amphibians. The system is used by these animals to extract information from the movements of water around their body, providing them with a sense of "touch-at-a-distance" that is involved in most aspects of fish behavior. Each neuromast has a core of mechanosensory hair cells, each of which is depolarized by water motion in one direction and hyperpolarized by motion in the other direction. Based on the position of their ganglion, two components of the lateral-line system can be distinguished: the anterior lateral-line (ALL) system comprises the neuromasts on the head and has its ganglion just anterior to the otic vesicle, the posterior lateral-line (PLL) system comprises the neuromasts on the body and tail and has its ganglion just posterior to the otic vesicle. The peripheral location of the PLL system makes it accessible and easily visualized by imaging methods. The PLL develops from the migrating primordium and so can be used to examine various aspects of neural development, including the control of long-range, collective cell migration and the mechanisms underlying the establishment of appropriate connectivity. Here we discuss imaging methods for exploring these processes.