The lateral line, an external sensory system composed of a network of hair cells arranged along the skin of fishes and aquatic amphibians, plays an important role in orientation and navigation in the aquatic environment. The current work examines lateral line functioning in tadpoles of the frog, Rana catesbeiana, and highlights the functional diversity of this system in different animal species. Recently hatched, early larval tadpoles were divided into an untreated group and a treated group immersed in gentamicin, an ototoxin that is expected to inactivate the lateral line hair cells. Animals from the gentamicin treated group were further divided into one of three post-treatment recovery groups: No Recovery (1 hour), 3-Day Recovery, and 7-Day Recovery. All animals were assessed behaviorally while exposed to the presence or absence of flow. Following behavioral assessment, the skin of a subset of animals from each treatment and recovery group were processed with two vital dyes to visualize neuromast structure and integrity. In addition, brains of some animals were processed for immunohistochemical labeling of apoptotic cells within lateral line target nuclei of the medulla. The current work demonstrates that bullfrog tadpoles respond to water flow in a manner that is less stereotyped than the typical responses seen in many species of fish. I also show that damage to the lateral line neuromasts disrupts flow-sensing behaviors, but that these behaviors do not fully recover in parallel with structural recovery of neuromasts, indicating a lasting behavioral effect of systemic hair cell death. Damage to tadpole lateral line hair cells disrupts normal orientation behavior at all but very high flow speeds. This is consistent with the structural and organizational changes within tadpole neuromasts seen as a result of gentamicin treatment. Levels of apoptosis within medullary target nuclei of the lateral line did not vary between different treatment and recovery groups. Apoptosis was consistently high in auditory nuclei, suggesting that these nuclei are more plastic during early development than are lateral line nuclei. These data have implications for our understanding of how important environmental signals are processed during a period of rapid developmental change.
Alexander, Erika E.,
"Orienting underwater: How Rana catesbeiana (American Bullfrog) tadpoles detect flow fields"
Psychology Theses and Dissertations.
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