Physiological responses of mechanosensory systems in the head of larval zebrafish (Danio rerio)

Abstract

The lateral line system of zebrafish consists of the anterior lateral line, with neuromasts distributed on the head, and the posterior lateral line, with neuromasts distributed on the trunk. The sensory afferent neurons are contained in the anterior and posterior lateral line ganglia, respectively. So far, the vast majority of physiological and developmental studies have focused on the posterior lateral line. However, studies that focus on the anterior lateral line, especially on its physiology, are very rare. The anterior lateral line involves different neuromast patterning processes, specific distribution of synapses, and a unique role in behavior. Here, we report our observations regarding the development of the lateral line and analyze the physiological responses of the anterior lateral line to mechanical and water jet stimuli. Sensing in the fish head may be crucial to avoid obstacles, catch prey, and orient in water current, especially in the absence of visual cues. Alongside the lateral line, the trigeminal system, with its fine nerve endings innervating the skin, could contribute to perceiving mechanosensory stimulation. Therefore, we compare the physiological responses of the lateral line afferent neurons to responses of trigeminal neurons and responsiveness of auditory neurons. We show that anterior lateral line neurons are tuned to the velocity of mechanosensory ramp stimulation, while trigeminal neurons either only respond to mechanical step stimuli or fast ramp and step stimuli. Auditory neurons did not respond to mechanical or water jet stimuli. These results may prove to be essential in designing underwater robots and artificial lateral lines, with respect to the spectra of stimuli that the different mechanosensory systems in the larval head are tuned to, and underline the importance and functionality of the anterior lateral line system in the larval fish head.

Multisensory strategies for postural compensation after lateral line loss

“…Larval zebrafish must instead gulp air at the water's surface to inflate the swim bladder 15 , maintaining volume by control of a sphincter at the junction of the pneumatic duct of the swim bladder and the esophagus 16 . Constitutive and early loss of the head neuromasts of the anterior lateral line 46,47 leads ~50% of larval zebrafish to over-inflate their swim bladders by gulping more air at the surface 38,48 . We propose that our copper treatment similarly affects the esophageal sphincter, leading to a transient secretion of gas that decreases the volume of the swim bladder.…”