Entoprocta

Barentsia laxa 1498941

Pedicellina cernua 001

Dinomischus

Entoprocta, also known as Kamptozoa, is a phylum of mostly marine, sessile, colonial animals, characterized by their unique feeding structure, the lophophore, a crown of ciliated tentacles surrounding the mouth but not the anus. The name "Entoprocta" comes from Greek, meaning "anus inside", which refers to the fact that the anus lies within the ring of tentacles, a distinctive feature differentiating them from the somewhat similar Bryozoa, with which they were once confused. Entoprocts are small, with individual zooids typically measuring less than 5 mm in size, and they are found in a variety of marine environments, from shallow coastal waters to deep sea.

Description

Entoprocts are characterized by their cup-shaped body, from which extends a stalk that attaches to a substrate or to other zooids within a colony. The body, or calyx, houses the internal organs and is crowned by the lophophore. The lophophore functions both in feeding, by creating currents to draw plankton and detritus towards the mouth, and in respiration. Entoprocts exhibit a simple level of organization, lacking a distinct head and specialized sensory organs. Their nervous system is a simple nerve net, and they have a U-shaped gut with the anus located close to the mouth, within the tentacle crown.

Reproduction and Lifecycle

Entoprocts can reproduce both sexually and asexually. Sexual reproduction involves the release of eggs and sperm into the water column, where fertilization occurs. Some species are hermaphroditic, possessing both male and female reproductive organs, while others have separate sexes. Asexually, they can reproduce through budding, where new individuals (zooids) form from the body of an existing one. The lifecycle of entoprocts includes a free-swimming larval stage, which settles onto a substrate and metamorphoses into the adult form.

Ecology

Entoprocts are found in a variety of marine environments, from tidal zones to depths of several hundred meters. They attach to hard substrates such as rocks, shells, or seaweed, and some species can even be found on other marine animals. Their feeding mechanism allows them to capture small particles, including plankton, from the water, playing a role in the aquatic food web. Entoprocts themselves are preyed upon by a variety of marine organisms, including fish and invertebrates.

Taxonomy

The phylum Entoprocta includes several hundred described species, divided among a handful of families. The taxonomy of entoprocts has been a subject of debate, with some researchers proposing that they should be classified within the larger group Lophotrochozoa, which also includes Mollusca, Annelida, and Bryozoa. This classification is based on molecular data and developmental similarities.

Conservation

While entoprocts are not typically the focus of conservation efforts, their presence and abundance can be indicators of environmental health and water quality. As sessile organisms, they are particularly susceptible to changes in their environment, including pollution and habitat destruction.