Is cyst formation in early eukaryotes a requirement for their preservation in the fossil record?

↓ Direkt till sidans innehåll
↓ Direkt till sidans sekundära innehåll (sidomenyn)

Sökning: WFRF:(Agić Heda 1989 ) > Is cyst formation i...

Agić, Heda,1989-Uppsala universitet,Paleobiologi (författare)

Is cyst formation in early eukaryotes a requirement for their preservation in the fossil record?

Artikel/kapitelEngelska2015

Förlag, utgivningsår, omfång ...

2015
electronicrdacarrier

Nummerbeteckningar

LIBRIS-ID:oai:DiVA.org:uu-256437
https://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-256437URI

Kompletterande språkuppgifter

Språk:engelska
Sammanfattning på:engelska

Ingår i deldatabas

SwePubSwePub

Klassifikation

Ämneskategori:ref swepub-contenttype
Ämneskategori:kon swepub-publicationtype

Anmärkningar

Most of the Archaean-Proterozoic fossil record consists of non-biomineralizing microorganisms or their signatures. Body fossils of bacteria and early eukaryotes are preserved in siliciclastics, shales and carbonates, and are usually studied by preparation of thin sections or extraction from the rock matrix via acid maceration.The first eukaryotic organic-walled microfossils (OWM) appear at least by 1.8 Ga and undergo morphological diversification and evolutionary radiation in the Mesoproterozoic. There are no preserved eukaryotic-grade microfossils except OWM until the onset of biomineralization much later in the Neoproterozoic, evident in the record of testate amoebae (VSM) and microfossils with scaly elements.OWM are a less conspicuous component of the fos-sil record than taxa with skeletal or shelly elements. Organic matter decays quickly upon death of the organism, due to autolytic enzymes or degradation via het-erotrophy. However, species producing vegetative cells, resting cysts, zygotes, or spores, show considerable resistance to autolysis. Case studies on extractable carbonaceous OWM indicate they are preserved due to complex refractory molecules in the structure of their sturdy vesicle walls. Living analogues across protistan clades utilise such sporopollenin-like compounds for the cyst wall construction during reproductive phase. Algaenan-containing trilaminar sheath structure (TLS) is secreted during aplanospore formation in extant chlorophyte alga Haematococcus. TLS has also been documented in Leiosphaeridia acritarchs from the Cambrian Lükati Formation in Estonia. Leiosphaeridia is a long ranging morphotype, dating as far back as 1.8 Ga. Presence of TLS in these fossils suggests their function as reproductive cyst. Dictyosphaera-Shuiyousphaeridium plexus from the Mesoproterozoic Ruyang Group, China, also exhibits cyst-like morphology and unique elements of wall reinforcement: internally secreted organic platelets.In addition to these early OWM, many Meso-Neoproterozoic taxa such as Tappania, Trachyhystrychosphaera and Kildinella contain cyst-like characters: 1) reproductive openings, 2) ornamentation, 3) occa-sionally preserved internal bodies and 4) acetolysis-resistant vesicle walls – properties observed among extant encysting protists.Ornamented (process-bearing) microfossils in par-ticular bear strong similarities with zygotes of living unicellular algae. Property of acetolysis-resistant vesicle is a result of sporopollenin-like macromolecules in the wall, synthesized most commonly by the autotrophic eukaryotes. Presence of such recalcitrant organic walls requires significant metabolic investment by the microorganism, which suggests a protective and/or reproductive function. This also allows for easier, and more detailed preservation in the rock record.One of the concerns arising from the studies on the early eukaryotic fossils is the bias towards encysting organisms. The eventual search for the fossil record on other planetary bodies could face the same challenges as the Precambrian palaeobiology: fossilisation and eventual detection might be problematic for any unicellular eukaryotic-grade organisms if they have not evolved reproduction via encystment, or cyst formation as means of coping with adverse environmental conditions.

Ämnesord och genrebeteckningar

NATURVETENSKAP Geovetenskap och miljövetenskap Geologi hsv//swe
NATURAL SCIENCES Earth and Related Environmental Sciences Geology hsv//eng
Proterozoic
early eukaryotes
fossilization
taphonomy

Biuppslag (personer, institutioner, konferenser, titlar ...)

Moczydłowska, MałgorzataUppsala universitet,Paleobiologi,ORIGINS AND EARLY DIVERSIFICATION OF PHOTOSYNTHETIC MICROBIOTA(Swepub:uu)malgvida (författare)
Uppsala universitetPaleobiologi (creator_code:org_t)

Sammanhörande titlar

Ingår i:Abstracts of the Astrobiology Science Conference 2015: Habitability, Habitable Worlds and Life

Internetlänk

http://www.hou.usra.edu/meetings/abscicon2015/pdf/7578.pdfhttp://www.hou.usra.edu/meetings/abscicon2015/pdf/7578.pdf
https://uu.diva-portal.org/smash/get/diva2:825359/FULLTEXT01.pdffulltext:postprint
https://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-256437

Till lärosätets databas

Hitta mer i SwePub

Av författaren/redakt...: Agić, Heda, 1989 ...; Moczydłowska, Ma ...

Om ämnet

NATURVETENSKAP: NATURVETENSKAP; och Geovetenskap och ...; och Geologi

Artiklar i publikationen: Abstracts of the ...

Av lärosätet: Uppsala universitet

Sök utanför SwePub

Sök vidare i:: Google; Google Book Search; Google Scholar

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

LIBRIS.kb.se