Sponges are not herbivores. In fact, they are not classified as herbivores, carnivores, or omnivores because they do not have a digestive system like animals do. Instead, sponges are filter feeders. They obtain their food by filtering tiny particles, such as bacteria and plankton, from the water that flows through their bodies.
Sponges have specialized cells called choanocytes, or collar cells, which have flagella that create water currents. These currents bring water into the sponge’s body through small pores called ostia. The choanocytes then trap and ingest the food particles from the water. After digestion, the nutrients are distributed throughout the sponge’s body.
So, while sponges do consume organic matter, they do so in a way that is quite different from how herbivores eat plants. This unique feeding method places them in a category of their own when it comes to how they obtain their nutrients.