There are about 6000 species of external anal animals.stayGeological ageThere are many kinds, fromCambrianIt has existed from early times to modern times and belongs to structural organism, with about 15000 fossil species.[1][4]
The bryozoan is small, not segmented, and has a specific cavity.There is a mouth in the front of the insect body, and there is a crown around the mouth, called "Zongdan", on which there are many tentacles.[2][9]
Bryozoans are group animals that live fixedly.Bryozoans areExternal anal phylum(scientific name: Ecoprosta).External anal animalUsed to be associated withInternal anal animalCollectively referred to asBryozoa(scientific name: Bryozoa)BryozoanIt has been specifically applied to external anal animals.[1]
Bryozoan is a kind of animal like moss plants, which looks like plants, but has a complete set of digestive organs, including the mouth, esophagus, stomach, intestine and anus.So put it in the animal kingdom.This organism is often associated with algae.Small, not segmented, specific cavity.A layer of colloid is secreted outside the body to form a group of bones.There is a mouth in the front of the insect body, and there is a crown around the mouth, called "Zongdan", on which there are many tentacles.The digestive tract is U-shaped, and the mouth is close to the anus.No excretory and circulatory organs.Both sea water and fresh water are produced.In geological times, there were many kinds,OrdovicianIt has already appeared, and there is still survival in modern times, such asFeather liverwortAttached to the lakeside rocks or plants;Peony bryozoans attach to shallow sea rocks.
In 2021, the early life research team of Northwest UniversityZhang ZhifeiProfessor team, announced in southern ShaanxiZhenba CountyThe discovery of the earliest known bryozoan (bryozoan) fossils on the earth has pushed the origin of bryozoans forward at least 50 million years, that is, the history of bryozoan origin has been pushed from the Ordovician toCambrianThe early stage of the outbreak.[4-5]
morphological character
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The external anal animal group is a primary insect or individual insect formed by attachment and metamorphosis of the larvae produced by sexual reproduction through asexual budding or germination of some dormant buds.According to the growth mode, it can be divided into two categories: upright type and coated type. Most external anal animals belong to the latter category.These groups lie flat on various substrates, most of which are simple in shape, thin and crusty, most of which are single layers.Double or multi-layer groups have more diverse shapes.The vertical population has a large degree of freedom of growth, and the population shape is complex. The common shapes are block, network, chain, fan, branch, and bush.There is a common phenomenon of similarity in external anal animal groups, that is, the same group type (such as reticular group and branching group) can occur in parallel in different species, genera, even families and orders.The external anal animals have a high adaptability to living environment, and even the same species will have population morphological variation due to different environmental conditions.[7-8]
Bryozoan structure
Growth environment
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Bryozoan
Moss insects mostly live in the sea.yesChrysanthemum dish moss insect、White lichenandLichen flagellatus, marine bryozoans in China are distributed inJiaozhou Bay, Zhejiang shallow sea bottom, mixed with coral.Freshwater bryozoans are found in fresh water bodies of Suzhou, Nanjing and Shenzhen.
Bryozoans like to live in clean water bodies rich in algae and dissolved oxygen. They can adapt to the temperature of various regions and are widely distributed around the world.Freshwater species grow vigorously in spring and autumn (25~28 ℃). There are many dormant buds on the water surface of the last year, and they develop into bryozoans in suitable environments.There are also bryozoans in slightly polluted water.If a large number of bryozoans appear during the biological pretreatment of micro polluted source water, they will be intercepted by the filler and grow on the filler, andVorticella 、Polycystis、Monotychium、Cladocera、CapillariaSuch protozoa with sticky tail stalks gather together, have a certain biological adsorption, and swallow micro organisms and organic impurities in the water, which has a certain positive effect on the purification of water.However, if it propagates in an extremely large amount, it will reduce the water flow speed and cause some adverse effects on the project operation.
Subordinate classification
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The external anal phylum is divided into three classes:
The hard body is calcareous, the worm tube is slender, and the cross section is round and polygonal, with clearance holes, puncture holes, central area (inner zone), and marginal area (outer zone). The boundary between the inner and outer zones is unclear, the inner zone wall is thick, and there are few transverse plates, the outer zone wall is thin, and there are many transverse plates.The wall of the insect tube has a parallel sheet structure around the insect chamber.
Bryozoan
Cryptostomata bryozoa
The hard body is calcareous, and the population is fan shaped, funnel shaped, branch shaped, etc. It is usually composed of many parallel branches connected by transverse branches to form a grid. There are two rows of insect chambers on the two branches, and the middle of the insect chamber is separated by a middle ridge.The insect chamber is rectangular, square or hexagonal, with clear inner and outer bands, narrow inner band, wide outer band, and puncture holes.It is dark brown under a single polarizer, and the wall has a parallel sheet structure.Bryozoans are distinguished from corals by their small population, slender insect tubes, and no outward contraction of their insect tubes, while their tube walls are in a pyramid like parallel sheet structure at the thickened part, with interstitial holes and pricking holes to distinguish coral algae and corals.The vast majority of bryozoans live in shallow sea, and a few live in fresh water.The era is from Ordovician to modern.[2]
Research progress
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Although the size of the bryozoan is small, about 0.5mm, they live in groups. A large number of bryozoans will form bryozoan groups in various shapes, such as branches, networks, sheets, and hemispheres.In their infancy, they often live a "tourist life", and then settle down to start a benthic or epiphytic life.Both modern and ancient bryozoans can be fixed on the hard rocky seabed, rolling pebbles or dead animal shells in various terrains.
The ancestors of the marine bryozoans can be traced back to the early Ordovician period about 500 million years ago.And a bryozoan fossil of early Ordovician Temadouk period was preserved in the Chinese Academy of SciencesNanjing Institute of Geology and Palaeontology(hereinafter referred to as Nangusuo).
Early Ordovician Temadouk bryozoan fossils
Early Ordovician Temadouk bryozoan fossils were discovered by researchers from the Nangu Institute in 2007 in the Fenxiang Formation in the Huanghuachang and Liujiachang areas of Yichang, Hubei Province.It is not only the oldest known bryozoan fossil in the world at that time, but also the skeleton organism that formed the earliest bryozoan reef in the worldEumetazoanBioherms.
Looking for bryozoans in earlier strata of the Early Ordovician (such as the Nanjinguan Formation) is not groundless.The fossil record shows that there are abundant bryozoans in Ordovician.In particular, the evolutionary radiation of Leptolabia bryozoans is an important component and embodiment of the Phanerozoic Paleozoic Ordovician biological radiation.In the early Ordovician Temadouk period, the bryozoans had a certain diversity, including three orders, namely, Metastomea, Cryptostomea and Estoniana, as well as three genera and six species, and their morphology was relatively complex.This indicates that there is a relatively long evolutionary period of bryozoa before the division of township groups.
However, this "earliest" record was not kept for a long time. Soon, through the continuous efforts of the Nangu Institute's bryozoan research group, an earlier bryozoan was found in the Nanjinguan Formation (the underlying stratum of the Fenxiang Formation) in the Liujiachang area of Songzi.
The earliest initiator of bryozoan research
In addition to the early Ordovician Temadouk bryozoan fossils, Nangu Institute has another indissoluble relationship with bryozoan fossils:Yang JingzhiHe is the first pioneer in the study of bryozoan fossils in China.
Big energy of small body
Modern research shows that the earliest bryozoan fossils were found in the early Ordovician strata.Among bryozoans, Ctenophora does not have calcium carbonate skeleton like other marine bryozoans, but has organic matter.Moreover, this group is regarded as a relatively primitive group, and other bryoids may derive from groups similar to Ctenophora.They have continued to modern times since the emergence of the Ordovician, but there are few changes and few fossils.
In the Paleozoic, bryozoans had three important evolutionary periods.
The first is the Ordovician, the first prosperous period of bryozoans.In this period, except for Ctenophora, the bryozoans appeared Metastomea, Vesicular Porea, Cryptostomea, Cyclostomea, etc.Among them, the diversity and biomass of the bryozoans of Metastomea and Cryptostomea are absolutely superior.
The Devonian to Carboniferous was the second prosperous period of bryozoans, and the above orders still existed, but Cryptostomata was particularly prosperous, and the order Panera bryozoans also gradually increased.
But in the third evolution period——permianThe bryozoan has undergone significant changes, which occurred at the end of the PermianMass extinctionThe former dominant groups, namely, Metastomata, Cryptostomata and Panera, have gradually disappeared, while the tracheostomia and labiostomia have begun to diversify and become the dominant group of bryozoans.In addition to the tracheostomiales and labiostomiales with calcium carbonate skeletons, bryozoans also include freshwater crustaceans and ctenophora bryozoans without mineralized skeletons.
The evolution of the morphology and diversity of bryozoans is one of the important reasons for researchers' interest. Another important reason is that bryozoans are a phylum with mineralized bones that did not appear in the Cambrian biological radiation."Therefore, the study of bryozoan paleontology is of great significance for scholars to understand the origin of metazoa.
In addition, bryozoans had considerable biodiversity in the Paleozoic and Cenozoic, which is of great significance for modern people to understand the coordinated evolution of biology and environment in the process of geological history.
In addition, bryozoans have a relatively fast evolution rate in individual geological periods, which can play an important role in stratigraphic correlation.
