Multiple choice

In which of the following organisms does the open circulatory system function as a hydrostatic skeleton?

  1. Sponges

  2. Molluscs

  3. Echinodermates

  4. Earthworms

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In molluscs and freshly molted aquatic arthropods, the open circulatory system functions as a hydrostatic skeleton.