Endoprocta

The phylum Endoprocta is a group of more than 100 species that closely resemble moss animals or members of the phylum Bryozoa. With the exception of the genus Urnatella all endoprocts are marine-dwelling species. Like bryozoans they are sessile, found attached to a wide range of submerged objects such as rocks, shells, sponges, corals, and other objects. These tiny animals—the largest measures just 0.2 in (5 mm) in length—may either live a solitary or colonial existence. All members of the phylum are filter feeders that extract plankton and other food particles from the water.

Body form is rather consistent with most species consisting of a stalk and an oval calyx surrounded by tentacles. Solitary species are usually positioned on a short stalk while colonial species may have a large number of individual animals all arising from a single, spreading stalk. The top of the animal is dominated by a ring of short tentacles which are produced directly from the body wall and which may be withdrawn when the animal is not feeding. The mouth is set to one side of the ring, the anus on the opposite side. As with other small, filter-feeding organisms, a mass of tiny cilia line the inner side of the tentacles. When they beat, they create a downward current drawing water and food particles towards the animal, in between the tentacles and towards the mouth. From here, additional cilia continue the downward movement of food items towards the stomach.

Asexual reproduction is common in both solitary and colonial species. Many endoprocts also produce male and female gametes. Fertilization is internal. Fertilized eggs develop into free-living larvae, which, can both swim and glide along the bottom. After a short period, the larva settles, attaches itself firmly to some substrate and undergoes metamorphosis.