In lakes with dragonfly larvae as predators, what is the effect of pelvic spines on predation?

• A. Pelvic spines may actually make sticklebacks easier to catch
• B. Pelvic spines make them safer from predation
• C. Pelvic spines have no effect
• D. Pelvic spines always prevent predation

Answer: (D)

Pelvic spines serve as a defense by making capture and handling more difficult for predators. Dragonfly larvae attack by extending their mouthparts to grasp prey and pull it into their jaws. Those spines protruding from the fish hinder the larva’s grip and complicate swallowing, reducing the likelihood of a successful attack. In lakes where dragonfly larvae are common, this defensive trait thus tends to prevent predation, giving spined sticklebacks a survival advantage. The other options conflict with how these predators capture prey, which is why this feature is seen as an effective deterrent in this predator-prey setup.