Osmotrophy

Osmotrophy is a feeding mechanism involving the movement of dissolved organic compounds by osmosis.

[1] Organisms that use osmotrophy include microorganisms like bacteria, many species of protists and most fungi.

Invertebrate animal groups like molluscs, sponges, corals, brachiopods and echinoderms may use osmotrophic feeding as a supplemental food source.

With bigger organisms, the surface-area-per-volume ratio drops and osmotrophy becomes insufficient to meet nutrient demands.

Larger, macroscopic organisms that rely on osmotrophy, compensate with a very flat, thin body.