BryozoaFrom Wikipedia, the free encyclopediaJump to navigationJump to search"Polyzoa" redirects here. For the tunicate genus, seePolyzoa (genus).BryozoaTemporal range: Early Ordovician –RecentPreЄЄOSDCPTJKPgN
"Bryozoa", fromErnstHaeckel'sKunstformen der Natur, 1904Scientific classificationKingdom:AnimaliaClade:LophophorataPhylum:BryozoaEhrenberg, 1831ClassesSee text.SynonymsEctoprocta (Nitsche, 1869)(formerly subphylum of Bryzoa)
Bryozoa(also known as thePolyzoa,Ectoproctaor commonly asmoss animals)areaphylumofaquaticinvertebrateanimals. Typically about 0.5 millimetres (0.020 in) long, theyarefilter feedersthat sieve food particles out of the water using a retractablelophophore, a "crown"oftentacleslined withcilia. Mostmarinespecies live in tropical waters, but a few occur inoceanictrenches, and others are found inpolarwaters. Oneclasslives only in a varietyoffreshwaterenvironments, and a few members of a mostly marine class preferbrackish water.Over 4,000 living species are known. Onegenusis solitary and the rest arecolonial.The phylum was originally called "Polyzoa", but this term was superseded by "Bryozoa" in 1831.Another group of animals discovered subsequently, whose filtering mechanism looked similar, wasalso included in "Bryozoa" until 1869, when the two groups were noted to be very different internally.The more recently discovered group was given the nameEntoprocta, while the original "Bryozoa"were called "Ectoprocta". However, "Bryozoa" has remained the more widely used term for the lattergroup.Individuals in bryozoan (ectoproct) colonies are calledzooids, since they are not fully independentanimals. All colonies contain autozooids, which are responsible for feeding andexcretion. Coloniesof someclasseshave various types of non-feeding specialist zooids, some of which are hatcheriesfor fertilized eggs, and some classes also have special zooids for defense of the colony. TheclassCheilostomatahave the largest number of species, possibly because they have the widestrange of specialist zooids. A few species can creep very slowly by using spiny defensive zooids aslegs. Autozooids supply nutrients to non-feeding zooids by channels that vary between classes. Allzooids, including those of the solitary species, consist of acystidthat provides the body wall andproduces theexoskeletonand apolypidethat contains the internal organs and the lophophore orother specialist extensions. Zooids have no special excretory organs, and the polypides ofautozooids are scrapped when the polypides become overloaded by waste products; usually thebody wall then grows a replacement polypide. In autozooids the gut is U-shaped, with the mouthinside the "crown" of tentacles and the anus outside it. Colonies take a variety of forms, includingfans, bushes and sheets. The Cheilostomata producemineralizedexoskeletons and form single-layered sheets which encrust over surfaces.