Other specialized cells, called collar cells, line the inside of the central cavity. The sponge body is full of holes – thousands of cells, each with a tiny pore ( porocytes) that brings seawater in through a small channel, called ostia, into the sponge’s central cavity called the spongocoel. There are also supportive collagen fibers called spongin. This simple skeleton is made up of tiny spicules that form from either calcium carbonate (calcareous) or silica (siliceous) depending upon the species of sponge. Between the two layers is a gelatinous matrix called mesohyl (or mesoglea) where the sponge’s “skeleton” forms. The collar cells (choanocytes) trap food particles, while specialized ameboid cells (ameboctes) digest the particles and transport the nutrients to other cells throughout the sponge. Though sponges were once thought to be completely sessile, scientists now know that some species can move very, very slowly.ĭiet: They are filter feeders, taking in seawater and filtering out the edible matter.īody Traits (Anatomy): Sponges are made up of 2 body layers – an outer layer of epidermal cells and an inner layer of collar cells. Habits: They are sessile – they do not move around but spend their lives anchored to one place. Habitat: They are mostly found attached to the ocean floor in shallow coastal waters, but some species live in freshwater habitats. They are very simple animals with no tissues, organs, or even a brain, but have specialized cells that perform their necessary nutritional, circulatory and reproductive functions. Most are asymmetrical (not regularly shaped), though a few form "radially symmetrical" shapes (which means they can be divided into similar halves if cut at any angle along a central axis, like a pie). There are more than 5,000 species of sponges and they come in all shapes and sizes.
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