|A BALANCING ACT: Ctenophore statocysts (1), consist of a statolith composed of lithocyte cells and four compound cilia called balancers that serve as the statolith’s legs. As the animal tilts in the water, the statolith falls to the side, bending the balancers and triggering a mechanical signal to adjust the frequency of ciliary beating along the ctenophore’s eight comb plates. Other invertebrates have a more complex statocyst, in which a sphere of sensory hair cells detects the movement of a statolith floating within it (2). When the statolith falls against a hair cell, it triggers an electrical impulse that sends the information to the animal’s central nervous system.|
|HAIRLINE: Modified epithelial cells called hair cells—similar to those in the mammalian inner ear—are the work horses of the lateral line in fishes. Hair cells connect to afferent neurons and are grouped together into structures called neuromasts whose hairs are covered by...|
ILLUSTRATIONS BY LAURIE O'KEEFE
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