関連する実験動画
Updated: May 26, 2026
09:15
Processing Embryo, Eggshell, and Fungal Culture for Scanning Electron Microscopy
Published on: August 16, 2019
化石化した核と発芽構造は,エディアカランの"動物胚"をプロティストを包み込むものとして識別する
Therese Huldtgren1, John A Cunningham, Chongyu Yin
1Department of Palaeozoology, Swedish Museum of Natural History, Stockholm, Sweden.
Science (New York, N.Y.)
|December 24, 2011
まとめ
以前は初期の動物胚と考えられていたエディアカランの化石は,非メタゾアンの発達パターンを表しています. これらの球状化石は,動物胚ではなく,非メタゾーン型ホロゾーンとして再分類されています.
科学分野:
- パレオントロジー・パレオントロジー
- 発達生物学 発達生物学とは
- 進化生物学の進化生物学について
背景:
- エディアカラン・ドゥシャントゥー形成の球状化石は,通常,初期のメタゾアンの胚として解釈されます.
- この解釈は,メタゾアンのシナポモルフィー,組織の分化,および関連する成体または若年形態の欠如によって異議を唱える.
研究 の 目的:
- ドウシャントウの球状化石の系統遺伝と発達状態を再評価する.
- これらの化石が初期の動物胚か,または別の進化の系統を表しているかどうかを判断する.
主な方法:
- シンクロトロンベースのX線トモグラフィック顕微鏡を用いて,化石の形態学と発達特徴を分析した.
- 比較的な発達分析は,現存するホロゾーン生物と実施した.
主要な成果:
- 化石は,多細胞メタゾーン胚と一致しない発達パターンを示しています.
- 発芽段階が特定され,メタゾア類の特徴的な分裂後の胚学を排除した.
- 特徴は,コアノフラゲレットやメソミケトゾーアなどの非メタゾーアホロゾーアと比べられる.
結論:
- ドウシャントウの球状化石は動物でも胚でもありません.
- それらは,全群ホロゾアまたは潜在的により遠い親類であるユカリオット内の進化的グレードを表しています.
- これらの化石におけるパリントミク分裂は,おそらく分散のためのプロパグールの生産に役立った.
関連する概念動画
01:27Diversity of Protists II
Alveolates are a group of organisms recognized by the presence of alveoli, which are cytoplasmic sacs located beneath the cell membrane. While their function remains uncertain, alveoli may help regulate water balance by controlling how much water enters and leaves the cell. In dinoflagellates, these structures may serve as armor plates. There are three major types of alveolates: ciliates, which move using cilia; dinoflagellates, which use flagella for movement; and apicomplexans, which are...
01:27Diversity of Protists III
Rhizaria are a diverse group of unicellular protists characterized by their threadlike cytoplasmic extensions known as pseudopodia. These structures aid in both locomotion and feeding, giving Rhizaria an amoeboid appearance. Their amoeboid morphology once led to taxonomic confusion, but molecular phylogenetics has clarified their evolutionary placement and emphasized their shared use of pseudopodia despite divergent lineages.This clade comprises diverse lineages such as Chlorarachniophyta,...
01:24Eukaryotic Evolution
The endosymbiont theory is the most widely accepted theory of eukaryotic evolution; however, its progression is still somewhat debated. According to the nucleus-first hypothesis, the ancestral prokaryote first evolved a membrane to enclose DNA and form the nucleus. Conversely, the mitochondria-first hypothesis suggests that the nucleus was formed after endosymbiosis of mitochondria.
Contrary to the endosymbiont theory, the eukaryote-first hypothesis proposes that the simpler prokaryotic and...
Contrary to the endosymbiont theory, the eukaryote-first hypothesis proposes that the simpler prokaryotic and...
01:27Overview of Protists
Protists are diverse eukaryotic microorganisms that lack the specialized tissues of plants and animals and the chitinous cell walls of fungi. Their early divergence within Eukarya resulted in structural, functional, and ecological diversity. They are classified into supergroups such as Archaeplastida, Excavata, Amoebozoa, Rhizaria, Alveolata, and Stramenopiles, determined through genetic analysis and structural similarities.Structural and Functional AdaptationsProtists have various adaptations...
02:33Seed Structure and Early Development of the Sporophyte
Seed structures are composed of a protective seed coat surrounding a plant embryo, and a food store for the developing embryo. The embryo contains the precursor tissues for leaves, stem, and roots. The endosperm and cotyledons—seed leaves—act as the food reserves for the growing embryo.
02:56The Fossil Record
The fossil record documents only a small fraction of all organisms that have ever inhabited Earth. Fossilization is a rare process, and most organisms never become fossils. Moreover, the fossil record only exhibits fossils that have been discovered. Nevertheless, sedimentary rock fossils of long-lived, abundant, hard-bodied organisms dominate the fossil record. These fossils offer valuable information, such as an organism's physical form, behavior, and age. Studying the fossil record helps...