Where would you expect to find the simplest body
plans?

Most sponge body plans are slight variations on a simple tube-within-a-tube design. which of the following is a key limitation of sponge body plans? sponges lack the specialized cell types needed to produce more complex body plans. the reliance on osmosis/diffusion requires a design that maximizes the surface area to volume ratio of the sponge. choanocytes must be protected from the hostile exterior environment. spongin cannot support heavy bodies.

Hydrosphere is the correct answer