What does the limnetic ecotype of sticklebacks primarily do in their habitat?

• A. Feeds near the bottom.
• B. Feeds in open water and has different jaw shapes and body proportions.
• C. Lives in saltwater environments.
• D. Has armor identical to benthic forms.

Answer: (B)

Limnetic sticklebacks are specialized for life in the open water of a lake. They feed on plankton and small organisms suspended in midwater, not near the bottom. To do this well, they develop traits that make cruising and catching prey efficient in open water, such as longer jaws and a more streamlined body that reduces drag while swimming. This open-water feeding role and its associated morphology distinguish them from benthic forms, which live and feed near the bottom.