Bryozoa

"Polyzoa" redirects here. For the tunicate genus, see Polyzoa (tunicate).

Bryozoa
Temporal range: Ordovician– Recent[1][2] Contested Cambrian records (Pywackia, Protomelission[3])
"Bryozoa", from Ernst Haeckel's Kunstformen der Natur, 1904
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Clade: Lophophorata
Phylum: Bryozoa
Ehrenberg, 1831[4]
Classes

See text.

Synonyms[5]

Ectoprocta (Nitsche, 1869) (formerly subphylum of Bryozoa)

Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals)[6] are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about 0.5 millimetres (1⁄64 in) long, they have a special feeding structure called a lophophore, a "crown" of tentacles used for filter feeding. Most marine bryozoans live in tropical waters, but a few are found in oceanic trenches and polar waters. The bryozoans are classified as the marine bryozoans (Stenolaemata), freshwater bryozoans (Phylactolaemata), and mostly-marine bryozoans (Gymnolaemata), a few members of which prefer brackish water. 5,869 living species are known.[7] Originally all of the crown group Bryozoa were colonial, but as an adaptation to a mesopsammal (interstitial spaces in marine sand) life or to deep-sea habitats, secondarily solitary forms have since evolved. Solitary species has been described in four genera; Aethozooides, Aethozoon, Franzenella and Monobryozoon). The latter having a statocyst-like organ with a supposed excretory function.[8][9]

The terms Polyzoa and Bryozoa were introduced in 1830 and 1831, respectively.[10][11] Soon after it was named, another group of animals was discovered whose filtering mechanism looked similar, so it was included in Bryozoa until 1869, when the two groups were noted to be very different internally. The new group was given the name "Entoprocta", while the original Bryozoa were called "Ectoprocta". Disagreements about terminology persisted well into the 20th century, but "Bryozoa" is now the generally accepted term.[12][13]

Colonies take a variety of forms, including fans, bushes and sheets. Single animals, called zooids, live throughout the colony and are not fully independent. These individuals can have unique and diverse functions. All colonies have "autozooids", which are responsible for feeding, excretion, and supplying nutrients to the colony through diverse channels. Some classes have specialist zooids like hatcheries for fertilized eggs, colonial defence structures, and root-like attachment structures. Cheilostomata is the most diverse order of bryozoan, possibly because its members have the widest range of specialist zooids. They have mineralized exoskeletons and form single-layered sheets which encrust over surfaces, and some colonies can creep very slowly by using spiny defensive zooids as legs.

Each zooid consists of a "cystid", which provides the body wall and produces the exoskeleton, and a "polypide", which holds the organs. Zooids have no special excretory organs, and autozooids' polypides are scrapped when they become overloaded with waste products; usually the body wall then grows a replacement polypide. Their gut is U-shaped, with the mouth inside the crown of tentacles and the anus outside it. Zooids of all the freshwater species are simultaneous hermaphrodites. Although those of many marine species function first as males and then as females, their colonies always contain a combination of zooids that are in their male and female stages. All species emit sperm into the water. Some also release ova into the water, while others capture sperm via their tentacles to fertilize their ova internally. In some species the larvae have large yolks, go to feed, and quickly settle on a surface. Others produce larvae that have little yolk but swim and feed for a few days before settling. After settling, all larvae undergo a radical metamorphosis that destroys and rebuilds almost all the internal tissues. Freshwater species also produce statoblasts that lie dormant until conditions are favorable, which enables a colony's lineage to survive even if severe conditions kill the mother colony.

Predators of marine bryozoans include sea slugs (nudibranchs), fish, sea urchins, pycnogonids, crustaceans, mites and starfish. Freshwater bryozoans are preyed on by snails, insects, and fish. In Thailand, many populations of one freshwater species have been wiped out by an introduced species of snail.[14] Membranipora membranacea, a fast-growing invasive bryozoan off the northeast and northwest coasts of the US, has reduced kelp forests so much that it has affected local fish and invertebrate populations.[15] Bryozoans have spread diseases to fish farms and fishermen. Chemicals extracted from a marine bryozoan species have been investigated for treatment of cancer and Alzheimer's disease, but analyses have not been encouraging.[16]

Mineralized skeletons of bryozoans first appear in rocks from the Early Ordovician period,[1] making it the last major phylum to appear in the fossil record. This has led researchers to suspect that bryozoans arose earlier but were initially unmineralized, and may have differed significantly from fossilized and modern forms. In 2021, some research suggested Protomelission, a genus known from the Cambrian period, could be an example of an early bryozoan,[17] but later research suggested that this taxon may instead represent a dasyclad alga.[3] Early fossils are mainly of erect forms, but encrusting forms gradually became dominant. It is uncertain whether the phylum is monophyletic. Bryozoans' evolutionary relationships to other phyla are also unclear, partly because scientists' view of the family tree of animals is mainly influenced by better-known phyla. Both morphological and molecular phylogeny analyses disagree over bryozoans' relationships with entoprocts, about whether bryozoans should be grouped with brachiopods and phoronids in Lophophorata, and whether bryozoans should be considered protostomes or deuterostomes.

  1. ^ a b Taylor, P.D.; Berning, B.; Wilson, M.A. (November 2013). "Reinterpretation of the Cambrian 'bryozoan' Pywackia as an octocoral". Journal of Paleontology. 87 (6): 984–990. Bibcode:2013JPal...87..984T. doi:10.1666/13-029. S2CID 129113026. Archived from the original on 7 June 2019. Retrieved 20 April 2018.
  2. ^ Ma, Junye; Taylor, Paul D.; Xia, Fengsheng; Zhan, Renbin (September 2015). "The oldest known bryozoan: Prophyllodictya (Cryptostomata) from the lower Tremadocian (Lower Ordovician) of Liujiachang, south-western Hubei, central China". Palaeontology. 58 (5): 925–934. Bibcode:2015Palgy..58..925M. doi:10.1111/pala.12189. S2CID 130040324.
  3. ^ a b Yang, Jie; Lan, Tian; Zhang, Xi-guang; Smith, Martin R. (8 March 2023). "Protomelission is an early dasyclad alga and not a Cambrian bryozoan". Nature. 615 (7952): 468–471. Bibcode:2023Natur.615..468Y. doi:10.1038/s41586-023-05775-5. PMID 36890226. S2CID 257425218.
  4. ^ Ernst, A. (2007). "A cystoporate bryozoan species from the Zechstein (Late Permian)". Paläontologische Zeitschrift. 81 (2): 113–117. Bibcode:2007PalZ...81..113E. doi:10.1007/BF02988385. S2CID 129637643.
  5. ^ Cite error: The named reference FuchsObstSundberg2009ComprMolPhyloOfBryozoa was invoked but never defined (see the help page).
  6. ^ Brusca, Richard C. (1980) [1973]. "21: The Lophophorate Phyla". Common intertidal invertebrates of the Gulf of California (revised & expanded, 2nd ed.). Tucson, AZ: University of Arizona Press. ISBN 9780816506828. OCLC 1029265317.
  7. ^ Bock, P.; Gordon, D.P. (August 2013). "Phylum Bryozoa Ehrenberg, 1831". Zootaxa. 3703 (1): 67–74. doi:10.11646/zootaxa.3703.1.14.
  8. ^ Schwaha, Thomas F.; Ostrovsky, Andrew N.; Wanninger, Andreas (June 2020). "Key novelties in the evolution of the aquatic colonial phylum Bryozoa: evidence from soft body morphology". Biological Reviews of the Cambridge Philosophical Society. 95 (3): 696–729. doi:10.1111/brv.12583. PMC 7317743. PMID 32032476.
  9. ^ Schwaha, Thomas; Bernhard, Joan M.; Edgcomb, Virginia P.; Todaro, M. Antonio (1 August 2019). "Aethozooides uraniae, a new deep-sea genus and species of solitary bryozoan from the Mediterranean Sea, with a revision of the Aethozoidae". Marine Biodiversity. 49 (4): 1843–1856. Bibcode:2019MarBd..49.1843S. doi:10.1007/s12526-019-00948-w. hdl:11380/1174838.
  10. ^ Thompson, John V. (1830). "Memoir V: On Polyzoa, a new animal discovered as an inhabitant of some Zoophites". Zoological researches and illustrations; or Natural history of nondescript or imperfectly known animals. Cork, IE: King and Ridings. pp. 89–102.
  11. ^ Ehrenberg, Christian G. (1831). "Pars zoologica. Animalia evertebrata exclusis insectis [Invertebrata other than Insecta]". Symbolae physicae, seu lcones et descriptiones corporum naturalium novorum aut minus cognitorum (in Latin). Berolini Ex officina Academica. pp. 1–126.
  12. ^ Stebbing, T.R.R. (1911). "The terms Polyzoa and Bryozoa". Proceedings of the Linnean Society of London. Session 123 (Symposium): 61–72.
  13. ^ Muir-Wood, H.M. (1955). A history of the classification of the phylum Brachiopoda. London: British Museum (Natural History). p. 13.
  14. ^ Cite error: The named reference predation_golden was invoked but never defined (see the help page).
  15. ^ Lauer, Antje (2016). "Watersipora subtorquata and the Possible Role of Its Associated Microbes: An Attempt to Explain the Extraordinary Invasion Success of This Marine Bryozoan Species". The Mechanistic Benefits of Microbial Symbionts. Advances in Environmental Microbiology. Vol. 2. Cham: Springer International Publishing. pp. 239–268. doi:10.1007/978-3-319-28068-4_9. ISBN 978-3-319-28066-0. Occasionally, the impact of an invertebrate invader can be substantial; such has been documented for Membranipora membranacea, a fast-growing invasive bryozoan species which has reduced kelp forests off the northeast and northwest coasts of the USA to an extent that it has affected local fish and invertebrate populations
  16. ^ "Introduction to the Bryozoa". Berkeley, CA: University of California Museum of Paleontology. Archived from the original on 8 December 2019. Retrieved 8 December 2019.
  17. ^ Zhang, Zhiliang; Zhang, Zhifei; Ma, J.; Taylor, P. D.; Strotz, L. C.; Jacquet, S. M.; Skovsted, C. B.; Chen, F.; Han, J.; Brock, G. A. (2021). "Fossil evidence unveils an early Cambrian origin for Bryozoa". Nature. 599 (7884): 251–255. Bibcode:2021Natur.599..251Z. doi:10.1038/s41586-021-04033-w. PMC 8580826. PMID 34707285. S2CID 240073948.