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Els ceratis (Ceratium) són un gènere de la família de les ceratícies.
Es caracteritza per les llargues prolongacions que presenten les plaques de la teca.
Ceratium ist eine Gattung der Dinoflagellaten aus der Ordnung Gonyaulacales. Die großen Einzeller leben in Salz- und Süßgewässern.
Die Zellen sind groß. Die Spitze des Episoms ist stark erhöht oder sogar zu einem Apikalhorn ausgebildet, das Hyposom weist zwei oder mehr Antapikalhörner auf. Das Cingulum liegt mehr oder weniger in der Mitte.[1]
Ceratium-Arten weisen gelb-braune Chloroplasten auf[1]. Bei meeresbewohnenden Arten kommt Anisogamie mit zygotischem Kernphasenwechsel vor. Vegetativ vermehren sie sich durch eine schräge Längsteilung, bei der die Panzerung schräg zum Sulcus gesprengt und durch die Zellen anschließend wieder ergänzt wird.[2]
Ceratium sind ausschließlich aquatisch vorkommende Organismen, die im Süß- und Salzwasser vorkommen. In großen Mengen können sie Auslöser einer sogenannten Roten Tide werden, bei der sie das Wasser braun färben. Einige Arten sind zur Biolumineszenz fähig[2].[1]
Ceratium ist eine Gattung der Dinoflagellaten aus der Ordnung Gonyaulacales. Die großen Einzeller leben in Salz- und Süßgewässern.
The genus Ceratium is restricted to a small number (about 7) of freshwater dinoflagellate species. Previously the genus contained also a large number of marine dinoflagellate species. However, these marine species have now been assigned to a new genus called Tripos.[1] Ceratium dinoflagellates are characterized by their armored plates, two flagella, and horns.[2] They are found worldwide and are of concern due to their blooms.
The genus was originally published in 1793 by Shrank, F. von Paula.[3] The taxonomy of Ceratium varies among several sources. One source states the taxonomy as: Kingdom Chromista, Phylum Miozoa, Class Dinophyceae, Order Gonyaulacales, and Family Ceratiaceae.[3] Another source lists the taxonomy as Kingdom Protozoa, Phylum Dinoflagellata, Class Dinophyceae, Order Gonyaulacales, and Family Ceratiaceae.[4] The taxonomic information listed on the right includes Kingdom Chromalveolate. Thus, sources disagree on the higher levels of classification, but agree on lower levels.
C. furcoides was originally named C. hirundinella var. furcoides Levander 1894, but is now C. furcoides (Levander) Langhans 1925. It - and C. hirundinella - are invasives in several river basins in South America.[5]
Ceratium species belong to the group of dinoflagellates known as dinophysiales, meaning they contain armored plates.[2] They contain a pellicle, which is a shell, that is made from the cell membrane and vesicles; vesicles are composed of cross-linked cellulose, forming the plates.[2] The pellicle divides into two structures known as the epicone and hypocone that lie above and below the transverse groove, the cingulum, respectively.[2] Two rows of plates surround the epicone and hypocone in a particular pattern that may be inherited by offspring.[2] These patterns may be used to identify groups of dinoflagellates or even species of Ceratium.[2]
The plates contain expanded horns, which is a characteristic feature of Ceratium species.[2] Species tend to have different shaped horns depending whether they are freshwater or marine species.[6] Their morphology depends on the temperature and salinity of the surrounding environment.[7] Species can be identified based on the shape of their horns. For instance, the species Ceratium tripos has horns that are U-shaped.[7]
Species of Ceratium contain two flagella of different lengths that are orientated in the transverse and longitudinal positions.[8] The transverse flagellum is structurally complex and wraps around the cingulum.[2] The movement of the flagellum is described as "wave-like" and allows the organism to spin as it swims.[2] The longitudinal flagellum extends from a groove known as the sulcus, and this flagellum is simpler in structure than the transverse flagellum.[2] The movement of this flagellum pulls the organism forward, but ultimately its movement is controlled by the viscosity of the water.[2]
Species of Ceratium have other structures called chromatophores, which contain red, brown, and yellow pigments used for photosynthesis.[9]
The average size of a Ceratium dinoflagellate is between 20–200 µm in length, which classifies it as belonging to the microplankton size category.[10]
Ceratiums have zygotic meiosis in their alternation of generation.
Ceratium dinoflagellates may reproduce sexually (two parent cells) or asexually (one parent cell) .[4] In asexual reproduction, the pellicle (shell) pulls apart and exposes the naked cell.[2] The cell then increases in size and divides, creating 4–8 daughter cells, each with two flagella.[2] The nuclear membrane is present throughout the process and the centrioles are not present, unlike many other eukaryotic organisms.[2] The nuclear membrane only divides when the waist of the organism constricts.[2]
In sexual reproduction, the cells of two organisms couple close to their sulci (longitudinal groove).[2] Meiosis occurs, which allows the chromosomes given by the haploid parents to pair.[2] Then diploid offspring, known as "swarmers", are released.[2]
Species of Ceratium are mixotrophic, meaning they are both photosynthetic and heterotrophic, consuming other plankton.[4]
Ceratium dinoflagellates have a unique adaptation that allows them to store compounds in a vacuole that they can use for growth when nutrients become unavailable.[11]
They are also known to move actively in the water column to receive maximum sunlight and nutrients for growth.[10] Another adaptation that helps growth includes the ability to extend appendages during the day which contain chloroplasts to absorb light for photosynthesis. At night, these organisms retract these appendages and move to deeper layers of the water column.[12]
Species of Ceratium are found across high and low latitudes,[6] but are commonly found in temperate latitudes.[13] Marine species found in warmer tropical seas in lower latitudes tend to have more branched horns than marine species found in the cold waters of higher latitudes.[6] The warm water of the tropics is less viscous, so marine species of Ceratium contain more branched horns in order to remain suspended in the water column.[6] The main function for the horns is to maintain buoyancy.
As lakes and ponds stratify in the summer due to a decrease in mixing, freshwater species of Ceratium tend to dominate the water column.[6]
Ceratium sp. are generally considered harmless and produce non-toxic chemicals.[14] Under certain conditions that promote rapid growth of the population, Ceratium sp. blooms known as Red Tides can deplete the resources and nutrients of the surrounding environment.[14] These blooms also deplete the dissolved oxygen in the water, which is known to cause fish kills.[15]
These dinoflagellates play important roles at the base of the food web. They are sources of nutrients for larger organisms and also prey on smaller organisms[14] such as diatoms.[2]
Worldwide, especially in higher latitudes, the frequency of red tides has increased, which may be due to human impacts on the coasts in terms of pollution.[2] As a result, dead fish from the oxygen-depleted water wash up on beaches, much to the dismay of people at resorts and hotels.[2]
The migration of these species has been impacted by global warming. Because the surface temperature of the ocean rises, these organisms move to deeper layers of the water column as they are temperature sensitive.[16] Due to this behavior, species of Ceratium are used as biological indicators because the deeper they are found in the water column, the greater the impact from global warming.[16]
The genus Ceratium is restricted to a small number (about 7) of freshwater dinoflagellate species. Previously the genus contained also a large number of marine dinoflagellate species. However, these marine species have now been assigned to a new genus called Tripos. Ceratium dinoflagellates are characterized by their armored plates, two flagella, and horns. They are found worldwide and are of concern due to their blooms.
Ceratium es un género de protistas dinoflagelados de la clase Dinophyceae, orden Gonyaulacales, familia Ceratiaceae, con dos flagelos heterocontos en el sulcus y el cíngulo. Las placas de la teca presentan prolongaciones largas. Sus células son asimétricas, comprimidas dorsiventralmente; placas gruesas y bien visibles, a menudo reticuladas, con procesos o cuernos, uno anterior y 2 o 3 posteriores; en la parte media ventral se localiza una placa gruesa y desarrollada, cromatóforos discoideos y numerosos.Las especies de este género junto con Peridinium, son las más comunes en la costa peruana; pocas son de agua dulce.
Datos: Q287907
Multimedia:
Especies: Ceratium (Chromista)
Ceratium é un xénero de protistas dinoflaxelados[1] da orde Gonyaulacales[2], que presenta dous flaxelos heterocontos no sulco e no cíngulo. As placas da teca presentan prolongacións moi longas. As súas células son asimétricas, comprimidas dorsiventralmente, con placas grosas e ben visibles, a miúdo reticuladas, con procesos ou cornos, un anterior e 2 ou 3 posteriores; na parte media ventral localízase unha placa grosa e desenvolvida. Con cromatóforos discoideos e numerosos amarelos, marróns ou verdes[3]. Presenta cloroplastos e son de cor amarelo-marrón.[4] Son especies acuáticas xeralmente de augas salgadas, e unhas poucas de auga doce. Algunhas especies poden proliferar en grandes cantidades orixinando mareas vermellas, aínda que non son tóxicos, e outras son bioluminescentes.[4][5]
Ceratium é un xénero de protistas dinoflaxelados da orde Gonyaulacales, que presenta dous flaxelos heterocontos no sulco e no cíngulo. As placas da teca presentan prolongacións moi longas. As súas células son asimétricas, comprimidas dorsiventralmente, con placas grosas e ben visibles, a miúdo reticuladas, con procesos ou cornos, un anterior e 2 ou 3 posteriores; na parte media ventral localízase unha placa grosa e desenvolvida. Con cromatóforos discoideos e numerosos amarelos, marróns ou verdes. Presenta cloroplastos e son de cor amarelo-marrón. Son especies acuáticas xeralmente de augas salgadas, e unhas poucas de auga doce. Algunhas especies poden proliferar en grandes cantidades orixinando mareas vermellas, aínda que non son tóxicos, e outras son bioluminescentes.
Ceratium is een geslacht van eencelligen uit de familie van de Ceratiaceae.
Ceratium is een geslacht van eencelligen uit de familie van de Ceratiaceae.
Ceratium é um género de protistas dinoflagelados[1] da ordem Gonyaulacales[2], que apresenta dois flagelos heterocontos no sulco e no cíngulo. As placas da teca apresentam longas extensões. As suas células são assimétricas, comprimidas dorsiventralmente, com placas grossas e bem visíveis, amiúde reticuladas, com processos ou cornos, um anterior e 2 ou 3 posteriores; na parte media ventral existe uma placa grossa e bem desenvolvida. Com cromatóforos discóides e numerosos amarelos, castanhos ou verdes[3]. Apresentam cloroplastos e são de cor amarela acastanhada.[4] São espécies aquáticas geralmente de águas salgadas, e outras de água doce. Algumas espécies podem proliferar em grandes quantidades originando marés vermelhas, não tóxicos, e outras bioluminescentes.[4][5]
Ceratium é um género de protistas dinoflagelados da ordem Gonyaulacales, que apresenta dois flagelos heterocontos no sulco e no cíngulo. As placas da teca apresentam longas extensões. As suas células são assimétricas, comprimidas dorsiventralmente, com placas grossas e bem visíveis, amiúde reticuladas, com processos ou cornos, um anterior e 2 ou 3 posteriores; na parte media ventral existe uma placa grossa e bem desenvolvida. Com cromatóforos discóides e numerosos amarelos, castanhos ou verdes. Apresentam cloroplastos e são de cor amarela acastanhada. São espécies aquáticas geralmente de águas salgadas, e outras de água doce. Algumas espécies podem proliferar em grandes quantidades originando marés vermelhas, não tóxicos, e outras bioluminescentes.
ケラチウム Ceratium は渦鞭毛藻類の1属。和名はツノオビムシ、あるいはツノモである。紡錘形の細胞体から前方に1本、後方に1-3本の角状突起を持つ。ほとんどは海産のプランクトンだが、淡水産の種もある。
単細胞の藻類で、鞭毛で遊泳する[1]。一部には連結した集団を作るものがある。細胞の表面にはセルロースの丈夫な鎧板がある。これは細胞中央を一周する横溝を隔てて上殻と下殻に分かれ、上殻は4枚の頂板と6枚の前帯板、下殻は6枚の後帯板と1枚の後挿間板と1枚の底板からなる。細胞本体はやや扁平でそこから角状の突起がでるのが大きな特徴である。上殻の先端からは上向きに前角が出る。これは本体とはっきり区別できるのが普通だが、なだらかに続いて区別が曖昧な例や、またこれを完全に欠く例もある。後殻からは後端部左右に2本の後角があるが、このうち1本が退化的なものや欠くもの、またもう1本が出るものなどがある。
海洋に種が多く、淡水産の種はごく少数にとどまる。
和名は幾つも提案されているが、多分に出入りがある。
これらの様子から、古くはウズオビムシを使ったことがあるが、近年はこの系統の名としてはツノオビムシを使うことが多いこと、別にツノモという名もそれなりに普及していることが分かる。また種名についてはかなり混乱しているように見える。本稿では混乱を避ける意もあり、揺れがない学名カナ読みを選んである。
この類では角の形に違いが多く、これによって分類が進められている。以下の亜属にわけられる[2]。
アーキーケラチウム亜属 Archaeceratium は上殻が平らに広がり、前角がない。海産で、フウセンツノオビムシ C. gravidium など。
ケラチウム亜属 Ceratium は、前角と２本の後角があり、それぞれの出た方向に真っ直ぐに伸びる。淡水産のマミズツノオビムシ C, hirundinella など。
アンフィケラチウム亜属 Amphyceratium は、3本の角を持つが、前角と左後角が特に長く発達し、全体として細長い棒状になっている。ユミツノオビムシ C. fuscus など。
ユーケラチウム亜属 Euceratium は2本の後ろ角が大きく曲がって前に伸び、そのために全体が碇の形になったもの。ツノオビムシ C. tripos など。
C. hirundinella・ケラチウム亜属
C. fusus・アンフィケラチウム亜属
ユーケラチウム亜属の1種
淡水では上記のように日本ではC. hirundinella とC. cornutum の2種が古くから知られる。ただし岡田他(1965)では、この両種共に普通種であると記しているのに対して、水野(1964)ではC. cornutum について、教科書などに取り上げられてはいるものの、実際には珍種である旨を記している。滋賀県の理科教材研究会編(2005)でも普通には前者しか見られないと記しており、この点では一致している。前者は角の長さや形など、形態的に変異が多いことも知られている。
海洋には遙かに多くの種があり、中でもツノオビムシ C. tripos は日本近海ではもっとも普通に見出される[3]。
ケラチウム Ceratium は渦鞭毛藻類の1属。和名はツノオビムシ、あるいはツノモである。紡錘形の細胞体から前方に1本、後方に1-3本の角状突起を持つ。ほとんどは海産のプランクトンだが、淡水産の種もある。
