Name: rhizaria: pseudopods, tests, and skeletons
Uploaded: 2025-06-12T06:30:33.000Z
Duration: 1 min 27 s
Channel: JoVE

Rhizaria reprezentują zróżnicowaną grupę protistów, którzy posiadają nitkowate pseudopodia. Istnieją trzy główne podgrupy - Chlorarachniophyta, Foraminifera i Radiolaria. Chlorarachniophyta to fototroficzne protisty występujące zarówno w środowisku słodkowodnym, jak i morskim. Mają chloroplasty z czterema błonami z powodu endosymbiontów glonów, które zostały nabyte podczas wtórnej endosymbiozy. Otwornice to stricte morskie protisty, które budują struktury przypominające muszle zwane testami, złożone z węglanu wapnia i materiału organicznego. Większość otwornic rozciąga się na zewnątrz od swoich testów, aby żywić się rozkładającą się materią organiczną, bakteriami lub innymi małymi protistami na dnie oceanu. Niektóre otwornice są planktoniczne i żywią endosymbiotyczne glony jako składniki odżywcze. Radiolarianie to morskie planktonowe chemoorganotrofy. Posiadają testy złożone z krzemionki. Promieniowce zamieszkują górne 100 m oceanu, gdzie pozostają zawieszone przez kropelki lipidów, duże cytoplazmatyczne wakuole i igiełkowate pseudopodia. Żywią się bakteriami i materią organiczną. W przeciwieństwie do tego, niektóre inne gatunki nawiązują symbiotyczne, ale nie endosymbiotyczne relacje z glonami.

różnorodność protistów – iii

Diversity of Protists III

Rhizaria to zr&#243;&#380;nicowana grupa jednokom&#243;rkowych protist&#243;w, charakteryzuj&#261;ca si&#281; nitkowatymi wypustkami cytoplazmatycznymi znanymi jako pseudopodia. Struktury te wspomagaj&#261; zar&#243;wno poruszanie si&#281;, jak i pobieranie pokarmu, nadaj&#261;c Rhizaria wygl&#261;d ameboidalny. Ich morfologia ameboidalna by&#322;a niegdy&#347; przyczyn&#261; trudno&#347;ci taksonomicznych, lecz filogenetyka molekularna wyja&#347;ni&#322;a ich pozycj&#281; ewolucyjn&#261; i podkre&#347;li&#322;a wsp&#243;lne wykorzystanie pseudopodi&#243;w pomimo rozbie&#380;nych linii rozwojowych.
Klad ten obejmuje zr&#243;&#380;nicowane linie ewolucyjne, takie jak Chlorarachniophyta, Radiolaria i Foraminifera, z kt&#243;rych ka&#380;da przystosowa&#322;a si&#281; do odmiennych nisz ekologicznych i wykazuje r&#243;&#380;norodne strategie metaboliczne.
Chlorarachniophyta
Chlorarachniophyta to jednokom&#243;rkowe, fototroficzne protisty wyst&#281;puj&#261;ce zar&#243;wno w &#347;rodowiskach morskich, jak i s&#322;odkowodnych. Stanowi&#261; przyk&#322;ad wt&#243;rnej endosymbiozy, w kt&#243;rej niezdolny do fotosyntezy eukariotyczny gospodarz poch&#322;on&#261;&#322; fotosyntetyzuj&#261;cego eukarionta algalnego. W przeciwie&#324;stwie do plastyd&#243;w pierwotnych, kt&#243;re zwykle posiadaj&#261; dwie b&#322;ony, chloroplasty chlorarachniofit&#243;w s&#261; otoczone czterema b&#322;onami i zawieraj&#261; nukleomorf &#8211; szcz&#261;tkowe j&#261;dro kom&#243;rkowe pochodz&#261;ce od poch&#322;oni&#281;tej algi. Nukleomorf ten reprezentuje rzadkie stadium po&#347;rednie w integracji plastyd&#243;w, zachowuj&#261;c genomowe i strukturalne &#347;lady zdarzenia endosymbiotycznego.
Architektura genetyczna chlorarachniofit&#243;w jest wyj&#261;tkowo z&#322;o&#380;ona. Wyst&#281;puje co najmniej pi&#281;&#263; genom&#243;w: (1) genom j&#261;drowy gospodarza, (2) genom mitochondrialny gospodarza, (3) genom nukleomorfu, (4) genom mitochondrialny algi oraz (5) genom plastydowy. W toku ewolucji wiele gen&#243;w endosymbionta zosta&#322;o przeniesionych do j&#261;dra gospodarza, co skutkuje redukcj&#261; genomu nukleomorfu i chloroplastu. Taka integracja genomowa odzwierciedla ewolucyjn&#261; optymalizacj&#281;, w ramach kt&#243;rej funkcje nadmiarowe s&#261; eliminowane lub przekierowywane.
Otwornice
Otwornice to morskie, ameboidalne protisty buduj&#261;ce z&#322;o&#380;one pancerzyki, cz&#281;sto zbudowane z w&#281;glanu wapnia. Pancerzyki te nie stanowi&#261; cz&#281;&#347;ci &#380;ywej kom&#243;rki, lecz zapewniaj&#261; ochron&#281; strukturaln&#261; i wspomagaj&#261; od&#380;ywianie przy pomocy pseudopodi&#243;w. Bentoniczne otwornice zamieszkuj&#261; dno oceaniczne, od&#380;ywiaj&#261;c si&#281; cz&#261;stkami materii organicznej i wchodz&#261;c w symbiozy zwi&#261;zane z wymian&#261; sk&#322;adnik&#243;w od&#380;ywczych z algami. Gatunki planktoniczne zawieraj&#261; fototroficzne endosymbionty i wyst&#281;puj&#261; w g&#243;rnych warstwach oceanicznych, gdzie dost&#281;pne jest &#347;wiat&#322;o s&#322;oneczne.
Zdolno&#347;&#263; pancerzyk&#243;w otwornic do fosylizacji czyni je niezast&#261;pionymi w biostratygrafii i geologii naftowej. Ich rozk&#322;ad w warstwach geologicznych umo&#380;liwia okre&#347;lenie wzgl&#281;dnego wieku osad&#243;w oraz ocen&#281; potencja&#322;u z&#322;&#243;&#380; ropy naftowej.
Promienice
Promienice to g&#322;&#243;wnie planktoniczne, morskie protisty zamieszkuj&#261;ce powierzchniowe wody oceaniczne. Ich symetryczne szkielety krzemionkowe s&#261; wysoce zdobione i pozostaj&#261; po &#347;mierci organizmu, przyczyniaj&#261;c si&#281; do powstawania krzemionkowego mu&#322;u dennego. Promienice od&#380;ywiaj&#261; si&#281; materi&#261; organiczn&#261; i bakteriami, a niekiedy tworz&#261; symbiotyczne relacje z algami. W przeciwie&#324;stwie do otwornic, promienice nie anga&#380;uj&#261; si&#281; w endosymbioz&#281;. Ich wyporno&#347;&#263; jest utrzymywana dzi&#281;ki inkluzjom lipidowym, wakuolom oraz sztywnym pseudopodiom, kt&#243;re przeciwdzia&#322;aj&#261; opadaniu pod wp&#322;ywem grawitacji.

Różnorodność protistów – III

Rhizaria to zr&#243;&#380;nicowana grupa jednokom&#243;rkowych protist&#243;w, charakteryzuj&#261;ca si&#281; nitkowatymi wypustkami cytoplazmatycznymi ...

Education

JoVE Core

Microbiology

Mikrobiologia

Unit

Jednostka

Microbial Diversity

Różnorodność mikrobiologiczna

KEY TERMS AND CONCEPTS

KLUCZOWE TERMINY I POJĘCIA

rhizaria: pseudopods, tests, and skeletons

Rhizaria are unicellular protists with threadlike pseudopodia, which are thin cytoplasmic extensions used for movement and feeding. Their amoeboid shape once caused taxonomic confusion, but molecular phylogenetics has since shown where they fit on the evolutionary tree. This group includes Chlorarachniophyta, Radiolaria, and Foraminifera, and each lineage has adapted to a different ecological niche and metabolic strategy.

Chlorarachniophyta are unicellular phototrophic protists found in marine and freshwater environments. They are a clear example of secondary endosymbiosis, where a non-photosynthetic eukaryotic host engulfed a photosynthetic algal eukaryote. Their chloroplasts have four membranes, unlike the two membranes seen in primary plastids, and they also keep a nucleomorph, which is the vestigial nucleus of the engulfed alga.

Chlorarachniophytes also have unusually complex genetics. At least five genomes are present: the host nuclear genome, the host mitochondrial genome, the nucleomorph genome, the algal mitochondrial genome, and the plastid genome. Over time, many genes moved from the endosymbiont to the host nucleus. This left the nucleomorph and chloroplast reduced and shows how cells can streamline after endosymbiosis.

Foraminifera are marine amoeboid protists that build tests, which are protective shells often made of calcium carbonate. The test is not part of the living cell, but it supports the cell and helps with feeding through pseudopodia. Benthic foraminiferans live on the ocean floor and feed on particulate organic matter, and some also form nutrient-exchange symbioses with algae.

Other foraminiferans are planktonic and live in the upper ocean where sunlight is available. These species can host phototrophic endosymbionts. Their tests fossilize well, which makes foraminifera useful in biostratigraphy and petroleum geology. Scientists use their fossils to compare the relative age of sediment layers and to help judge where oil deposits may be found.

Radiolaria are mostly planktonic marine protists found in surface waters. They have ornate, symmetrical skeletons made of silica, and these structures remain after death to form siliceous ooze on the seafloor. Radiolarians feed on organic detritus and bacteria, and some live with algae in symbiosis. Unlike foraminifera, they do not use endosymbiosis. Their buoyancy comes from lipid inclusions, vacuoles, and stiff pseudopodia that help keep them from sinking.

Rhizaria: Pseudopods, Tests, and Skeletons

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diversity of protists ii

Alveolates: Ciliates, Dinoflagellates, Apicomplexans

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diversity of protists iii

Rhizaria are unicellular protists with threadlike pseudopodia, which are thin cytoplasmic extensions used for movement and feeding. Their amoeboid shape once caused taxonomic confusion, but molecular phylogenetics has since shown where they fit on the evolutionary tree. This group includes Chlorarachniophyta, Radiolaria, and Foraminifera, and each lineage has adapted to a different ecological niche and metabolic strategy. Chlorarachniophyta are unicellular phototrophic protists found in marine...

diversity of protists iv

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,...

key terms and concepts

Explore Rhizaria in high school biology, including pseudopodia, chlorarachniophytes, foraminifera, and radiolarians with their unique structures and roles.

Rhizaria: Pseudopods, Tests, and Skeletons | 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

Rhizaria: Pseudopods, Tests, and Skeletons

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