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What types of scales cover the body of a typical trout?
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protacanthopterygian
Rainbow trout (Oncorhynchus mykiss).
A typical trout is covered with small, smooth cycloid scales. These scales are thin, overlapping plates located within the dermis of the fish's skin.12
In trout, these scales are deposited in a series of annual rings, reflecting growth patterns that typically occur more rapidly during the spring and summer months. Additionally, the lateral line nervous system—which functions as a pressure receptor and direction finder—consists of sensory cells embedded beneath these scales along the midline of the fish's body, connecting to the surface through pores in the scales.23