Which sensory appendages around the mouth show a distinct color difference between the upper and lower jaws?
Answer
The barbels
The barbels on the upper jaw are typically dark, matching the upper body coloration, while the lower jaw barbels are usually lighter or whitish.

Related Questions
What is the scientific name for the flathead catfish?How is the mouth configuration of the flathead catfish best described?What specific characteristic distinguishes the dorsal fin of the flathead catfish?How does the tail fin of the flathead catfish typically compare to that of the blue catfish?What coloration pattern is generally absent on healthy, adult flathead catfish?Which sensory appendages around the mouth show a distinct color difference between the upper and lower jaws?What feature is cited as the most reliable, non-size-dependent identifier for young flathead catfish compared to young channel catfish?What is the typical range of coloration for the belly (ventral surface) of a flathead catfish?What is the documented potential maximum weight that large flathead specimens can approach or exceed?What is contained within the pectoral fins that requires careful handling?