Name: amoebozoa: movement and life cycles
Uploaded: 2025-06-05T06:27:20.000Z
Duration: 1 min 27 s
Channel: JoVE

Amöbozoen-Protisten zeichnen sich durch ihre lappenförmigen Pseudopodien aus. Es umfasst Gymnamoeben, Entamoebas sowie plasmodiale und zelluläre Schleimpilze. Gymnamoebas, wie Amöben-Spezies, sind freilebende Protisten, die in Wasser- und Bodenumgebungen leben. Im Gegensatz dazu sind Entamoeben parasitär und bewohnen hauptsächlich die Mundhöhle oder den Darmtrakt von Wirbeltieren und Wirbellosen. Der humanpathogene Entamoeba histolytica ist ein bemerkenswertes Beispiel. Schleimpilze sind bewegliche, pilzähnliche Protisten, die Fruchtkörper produzieren, die Sporen zur Ausbreitung enthalten. Plasmodiale Schleimpilze wie Physarum existieren typischerweise als eine einzelne Masse, die als Plasmodium bekannt ist, in ihrem vegetativen Stadium, das mehrere diploide Kerne enthält. Ein Plasmodium ist beweglich und produziert Sporangien, die haploide Sporen enthalten. Unter günstigen Bedingungen entwickeln sich diese Sporen zu geißeligen Schwarmzellen, die sich zu einem diploiden Plasmodium verschmelzen. Im Gegensatz dazu existieren zelluläre Schleimpilze wie Dictyostelium als einzelne haploide Zellen in ihrem vegetativen Zustand. Wenn sie verhungern, lagern sie sich zusammen, bilden bewegliche Massen und verwandeln sich in Fruchtkörper.

diversität der protisten-iv

Diversity of Protists IV

Amoebozoa stellen eine vielf&#228;ltige Gruppe terrestrischer und aquatischer Protisten dar, die lappenf&#246;rmige Pseudopodien zur Fortbewegung und Nahrungsaufnahme nutzen. Dieses Merkmal unterscheidet sie von den Rhizaria, die fadenf&#246;rmige Pseudopodien besitzen. Die Hauptklassifikationen innerhalb der Amoebozoa umfassen Gymnamoeben, Entamoeben sowie die plasmodialen und zellul&#228;ren Schleimpilze. Phylogenetische Belege deuten darauf hin, dass sich die Amoebozoa aus einer Linie entwickelten, die letztlich zu Pilzen und Tieren f&#252;hrte.
Gymnamoeben und Entamoeben
Gymnamoeben sind freilebende Protisten, die in aquatischen und terrestrischen Umgebungen vorkommen. Ihre am&#246;boide Bewegungweise erfolgt mittels Pseudopodien und beruht auf zytoplasmatische Str&#246;me. Dabei bewegt sich das Zytoplasma in einem weniger kontrahierten und fl&#252;ssigeren Bereich an der Vorderseite der Zelle entlang des Weges des geringsten Widerstandes. Dieser Str&#246;mungsprozess wird durch Mikrofilamente unterst&#252;tzt, die sich direkt unterhalb der zytoplasmatischen Membran befinden. Gymnamoeben variieren erheblich in ihrer Gr&#246;&#223;e und reichen von nur 15 Mikrometern im Durchmesser bis &#252;ber 750 Mikrometer &#8211; letztere sind mit blo&#223;em Auge sichtbar.
Im Gegensatz zu freilebenden Gymnamoeben sind Entamoeben parasitische Protisten, die haupts&#228;chlich die Mundh&#246;hle oder den Darmtrakt von Wirbeltieren und Wirbellosen besiedeln. Besonders erw&#228;hnenswert ist Entamoeba histolytica, eine humanpathogene anaerobe Am&#246;bienart, die die am&#246;bische Ruhr verursacht. Diese Erkrankung f&#252;hrt zur Ulzeration des Darmtrakts und ruft blutige Durchf&#228;lle hervor. Die &#220;bertragung dieses Parasiten erfolgt &#252;ber Zysten, die durch f&#228;kale Kontamination von Wasser, Lebensmitteln und Essgeschirr verbreitet werden.
Schleimpilze
Schleimpilze wurden historisch aufgrund &#228;hnlicher Lebenszyklen und der Bildung von Fruchtk&#246;rpern, die Sporen zur Verbreitung enthalten, mit Pilzen klassifiziert. Im Gegensatz zu Pilzen zeigen Schleimpilze jedoch Motilit&#228;t und k&#246;nnen sich rasch &#252;ber feste Oberfl&#228;chen bewegen. Diese Organismen werden in zwei Hauptgruppen unterteilt: plasmodiale Schleimpilze, auch als azellul&#228;re Schleimpilze bekannt, und zellul&#228;re Schleimpilze.
Plasmodiale Schleimpilze existieren in ihrem vegetativen Stadium als amorphe Masse aus Protoplasma, das als Plasmodium bezeichnet wird (nicht zu verwechseln mit dem pathogenen Genus Plasmodium, das Malaria verursacht) und mehrere diploide Zellkerne enth&#228;lt. Dieses Plasmodium ist aktiv motil und breitet sich durch am&#246;boide Bewegung aus. Unter g&#252;nstigen Bedingungen bildet es Sporangien &#8211; Strukturen, die haploide Sporen enthalten. Diese Sporen keimen und entwickeln sich zu begei&#223;elten Schw&#228;rmerzellen, die anschlie&#223;end fusionieren, um ein diploides Plasmodium zu regenerieren. Ein bekanntes und gut untersuchtes Genus ist Physarum.
Zellul&#228;re Schleimpilze hingegen verbleiben im vegetativen Zustand als einzelne haploide Zellen und bilden nur unter bestimmten Umweltbedingungen diploide Strukturen. Die gut untersuchte Art Dictyostelium discoideum durchl&#228;uft einen asexuellen Lebenszyklus, der durch Aggregation, Migration und Fruchtk&#246;rperbildung gekennzeichnet ist. Als Reaktion auf Nahrungsmangel aggregieren einzelne Dictyostelium-Zellen zu einem Pseudoplasmodium, in dem die Zellen ihre Individualit&#228;t verlieren, ohne miteinander zu fusionieren. Der Aggregationsprozess wird durch die Freisetzung von cyclischem Adenosinmonophosphat (cAMP) ausgel&#246;st &#8211; ein Signalmolek&#252;l, das benachbarte Zellen anzieht. Die aggregierte Zellmasse, bekannt als &#8222;Slug&#8220;, zeigt zun&#228;chst Motilit&#228;t, wird dann station&#228;r und richtet sich vertikal aus, woraufhin die Fruchtk&#246;rperbildung eingeleitet wird.
Der Fruchtk&#246;rper besteht aus einem Stiel und einem Kopf. Stielzellen synthetisieren Zellulose, was strukturelle Stabilit&#228;t verleiht, w&#228;hrend sich die Kopfzellen zu Sporen differenzieren. Nach der Verbreitung keimen diese Sporen und entwickeln sich zu neuen am&#246;boiden Zellen, wodurch der Lebenszyklus fortgesetzt wird. Neben der asexuellen Fortpflanzung kann Dictyostelium auch sexuelle Fortpflanzung betreiben, bei der zwei Am&#246;ben zu einer einzigen Riesenam&#246;be fusionieren. Diese Struktur entwickelt eine dicke Zellulosewand und bildet eine Makrozyste, die &#252;ber lange Zeitr&#228;ume hinweg ruhen kann. Schlie&#223;lich erfolgt innerhalb der Makrozyste eine Meiose, bei der haploide Kerne entstehen, die sich in neue Am&#246;ben integrieren, womit der asexuelle Zyklus erneut beginnt.

Diversität der Protisten-IV

Amoebozoa stellen eine vielf&#228;ltige Gruppe terrestrischer und aquatischer Protisten dar, die lappenf&#246;rmige Pseudopodien zur Fortbewegung und ...

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amoebozoa: movement and life cycles

Amoebozoa are a diverse group of terrestrial and aquatic protists. They move and feed with lobe-shaped pseudopodia. This feature sets them apart from Rhizaria, which have threadlike pseudopodia. The group includes gymnamoebas, entamoebas, and the plasmodial and cellular slime molds. Phylogenetic evidence also shows that Amoebozoa split from a lineage that later gave rise to fungi and animals.

Gymnamoebas are free-living protists that live in water and soil. They move by amoeboid movement, which depends on pseudopodia and cytoplasmic streaming. In this process, the cytoplasm flows into a less contracted, more fluid region at the front of the cell. Microfilaments just under the cell membrane support this movement. Gymnamoebas also vary widely in size, from about 15 micrometers across to more than 750 micrometers, which can be seen with the naked eye.

Entamoebas are parasitic protists that usually live in the mouth or intestinal tract of vertebrates and invertebrates. Entamoeba histolytica is an anaerobic species and a human pathogen. It causes amebic dysentery, which can ulcerate the intestinal tract and lead to bloody diarrhea. The parasite spreads through cysts that contaminate water, food, and eating utensils.

Slime molds were once grouped with fungi because both can form fruiting bodies that contain spores. Unlike fungi, however, slime molds can move quickly across solid surfaces. They are divided into plasmodial slime molds, also called acellular slime molds, and cellular slime molds. These two groups have different life cycles, but both use spore formation for dispersal.

Plasmodial slime molds live as a plasmodium in the vegetative stage. A plasmodium is an amorphous mass of protoplasm with many diploid nuclei, and it moves by amoeboid movement. When conditions are favorable, it forms sporangia that contain haploid spores. These spores germinate into flagellated swarm cells, which then fuse to form a new diploid plasmodium. Physarum is a well-known genus in this group.

Cellular slime molds stay as individual haploid cells during the vegetative stage. Under certain environmental conditions, they form diploid structures. Dictyostelium discoideum is the best-studied species in this group. Its asexual life cycle includes aggregation, migration, and fruiting body formation, and it can also undergo sexual reproduction. During starvation, cells release cAMP, or cyclic adenosine monophosphate, which attracts nearby cells and triggers aggregation into a pseudoplasmodium. The cells do not fuse, but they lose their individuality and form a moving slug.

The slug later becomes stationary and stands upright before fruiting body formation begins. The fruiting body has a stalk and a head. Stalk cells make cellulose for support, while head cells become spores. After dispersal, the spores germinate into new amoeboid cells. Dictyostelium can also reproduce sexually when two amoebae fuse to form a giant amoeba. This structure develops a thick cellulose wall and becomes a macrocyst that can stay dormant for a long time. Meiosis then occurs inside the macrocyst, producing haploid nuclei that give rise to new amoebae and restart the asexual cycle.

Amoebozoa: Movement and Life Cycles

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diversity of protists iii

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diversity of protists iv

Amoebozoa are a diverse group of terrestrial and aquatic protists. They move and feed with lobe-shaped pseudopodia. This feature sets them apart from Rhizaria, which have threadlike pseudopodia. The group includes gymnamoebas, entamoebas, and the plasmodial and cellular slime molds. Phylogenetic evidence also shows that Amoebozoa split from a lineage that later gave rise to fungi and animals. Gymnamoebas are free-living protists that live in water and soil. They move by amoeboid movement,...

key terms and concepts

Learn how Amoebozoa move with pseudopodia and how gymnamoebas, entamoebas, and slime molds grow, spread, and reproduce in different life cycles.

Amoebozoa: Movement and Life Cycles | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Amoebozoa: Movement and Life Cycles

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