Which morphological trait is most strongly associated with diet specialization in sticklebacks?

Which morphological trait is most strongly associated with diet specialization in sticklebacks?

• A. Jaw length
• B. Gill raker number and morphology
• C. Eye size
• D. Dorsal fin height

Answer: (B)

Gill raker number and morphology is the trait most tightly linked to what a stickleback eats. Gill rakers are the bony or cartilaginous projections along the inner gill arches that act like a sieve as water and prey pass through. The spacing, size, and stiffness of these rakers determine which prey sizes can be captured and retained while filtering out water. Populations that specialize on tiny prey like zooplankton tend to evolve more numerous and finer gill rakers to efficiently trap small particles. In contrast, populations feeding on larger prey or requiring quick handling often have fewer or coarser gill rakers, which suits their diet better. While jaw length, eye size, and dorsal fin height can influence feeding or locomotion in various ways, the gill raker system shows the strongest and most direct association with diet specialization.

Gill raker number and morphology is the trait most tightly linked to what a stickleback eats. Gill rakers are the bony or cartilaginous projections along the inner gill arches that act like a sieve as water and prey pass through. The spacing, size, and stiffness of these rakers determine which prey sizes can be captured and retained while filtering out water. Populations that specialize on tiny prey like zooplankton tend to evolve more numerous and finer gill rakers to efficiently trap small particles. In contrast, populations feeding on larger prey or requiring quick handling often have fewer or coarser gill rakers, which suits their diet better. While jaw length, eye size, and dorsal fin height can influence feeding or locomotion in various ways, the gill raker system shows the strongest and most direct association with diet specialization.