Moss animals

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Moss animals
Moss animals, from Ernst Haeckel, art forms of nature

Moss animals, from Ernst Haeckel, art forms of nature

without rank: Multicellular animals (Metazoa)
without rank: Tissue animals (Eumetazoa)
without rank: Bilateria
without rank: Primordial mouths (protostomia)
Over trunk : Lophotrochozoa (Lophotrochozoa)
Trunk : Moss animals
Scientific name
Ehrenberg , 1831

Moss animals (Ectoprocta ( size : with outer anus )), also called Bryozoa or Polyzoa , are multicellular animals that live in water. Due to their microscopic size, individual animals are difficult to make out, but larger colonies can easily be recognized as a flat structure, for example on stranded seaweed .

Moss animals belong to the Lophotrochozoa , a large group of the primordial mouths (Protostomia). Their exact relationship to other Lophotrochozoa strains is currently unclear. Neither the often assumed relationship to the cupworms (Entoprocta), nor to the horseshoe worms (Phoronida) and arm pods (Brachiopoda) could be confirmed by molecular genetic test methods. In older textbooks they are often found combined with the Phoronida and Brachiopoda to form the Tentaculata tribe .


Anatomy of a bogus

Moss animals usually form colonies (zoarium) from several individual animals ( zooids ). The individual zooid consists of a soft body and a protective shell, the extra-zooidal skeleton ( zooecium ) surrounding it. The soft body consists of the polypid (= front body; freely moving parts) and the cystid (= rear body; into which the polypid can be completely drawn in by means of the retracting muscles). The polypid is formed from the cystid. The digestive system is divided into the mouth, midgut, rectum and anus. The anus is not terminal, but comes to lie outside of the tentacle ring (called lophophor) through the U-shaped intestine near the mouth. The mouth is surrounded by tentacles that sit on a circular or two-part lophophor. The intestinal canals of the individual animals are not connected to one another as in the cnidarian colonies .

There is a division of labor within the colonies. Severely regressed animals form stems, tendrils or root threads. Other individual animals form sex cells, still others become ammenties or avicularia or vibracularia , which are similar to bird's heads and which prevent foreign organisms from settling on the colony. In the specialized animals of the colony, both the tentacle crown and usually the intestine have receded.

Reproduction and development

Fossil bog animals

The animals can reproduce sexually or asexually.

Sexual reproduction

Sexual reproduction gives rise to two different types of larvae : The planktotrophic larva known as the cyphonaut is the "primitive" form. It feeds on food particles in the plankton for weeks or even months . The lecitothrophic larva attaches itself to the ventral surface after a few hours. Through metamorphosis occurs ancestrula , the first 1-6 zooids a new colony. This is then followed by asexual reproduction, through which the colony continues to grow.

Asexual reproduction

Asexual reproduction occurs through buds , similar to that of a plant, which in freshwater species are called statoblasts . This can create large colonies. The zooids resulting from asexual reproduction within a colony are consequently clones , genetically identical offspring of the original larva.


Today about 5,600 recent and 16,000 fossil species of bog animals have been described in fresh and salt water. The class of freshwater molluscs (Phylactolaemata) includes all limnic species.

In geology , due to their widespread use since the Ordovician ( Cyclostomata and Ctenostomata ), they are of great importance as reference fossils and for stratigraphic determinations.

Economical meaning

Over 125 species cause damage and maintenance costs to ships, port facilities and water management systems (partly also in fresh water) due to strong growth.

On the other hand, bryozoa produce chemical agents that are the subject of medical research with regard to their effects, including the possible anti-cancer drug bryostatin 1 .

Web links

Commons : Moostierchen  - Collection of images, videos and audio files


  • Hayward, PJ, & Ryland, JS, 1999: Cheilostomatous Bryozoa. Part 2. Hippothoidea - Celleporoidea. Synopses of the British Fauna (New Series), 14: 1-416, (Barnes, RSK, & Crothers, JH, editors). Field Studies Council, Shrewsbury.