関連する実験動画
Updated: May 24, 2026

09:15
Processing Embryo, Eggshell, and Fungal Culture for Scanning Electron Microscopy
Published on: August 16, 2019
コメント on "化石化した核と発芽構造は,エディアカランの"動物胚"をエンキスティング原生体として識別する"
Shuhai Xiao1, Andrew H Knoll, James D Schiffbauer
1Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA. xiao@vt.edu
まとめ
ドウシャントウの微生物化石が再調査され,初期の動物として分類されることに異議を唱える. この研究は,内部構造が核ではなく,異なる生物を代表する可能性があることを示唆し,メソミケトゾーア比較に疑問を投げかけている.
科学分野:
- パレオントロジー・パレオントロジー
- 進化生物学の進化生物学について
- 微生物学 微生物学とは
背景:
- ドゥシャントゥオ群には,謎のネオプロテロゾイク期の微生物化石が含まれています.
- 以前の研究では,これらの微生物化石が初期の動物胚 (ホロゾーア) を代表することを示唆していた.
- 2011年の研究では,内部構造を推定した結果,メソミケトゾーアとの親和が示唆された.
研究 の 目的:
- ドウシャントウの微生物化石の解釈を再評価する.
- これらの化石に関するメソミケトゾーア仮説を批判的に評価する.
- 微生物化石内の内部構造の性質を調査する.
主な方法:
- ドウシャントウの微生物化石標本の顕微鏡分析.
- 既知の微生物とメタゾーン生物との比較分析.
- 化石の保存とサイズ制限の検討.
主要な成果:
- 内部構造は小さすぎるし,保存状態が悪いため,核として明確に識別できません.
- 証拠は,研究された標本の中で少なくとも2つの異なる集団の存在を示唆しています.
- いくつかの標本では,メソミケトゾーア類との親和に矛盾する擬似パレンキマト組織を示している.
結論:
- ドウシャントウの微生物化石をメソミケトゾーアとして解釈することは疑わしい.
- サイズと保存に関する問題は,内部構造の識別を制限します.
- ドウシャントウの微生物化石は,以前提案されたものより複雑で多様な集合体を表している可能性が高い.
関連する概念動画
Diversity 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,...
Eukaryotic 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...
Diversity 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...
Overview 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...
The Tree of Life - Bacteria, Archaea, Eukaryotes
The “tree of life” describes the evolution of life and the evolutionary relationships between organisms. The root of the tree is the common ancestor to all life on Earth. All other species radiate from this point, much like the branches of a tree. The numerous tips of these branches on the tree of life represent every living, or extant, species. Extinct species, which are species that no longer exist, can be found towards the center of the tree. Currently, these organisms, both extant and...
Diversity of Protists I
Excavata is a diverse group of protists that includes both chemoorganotrophic and phototrophic species, with some thriving in anaerobic environments. Among the key groups within Excavata are diplomonads and parabasalids, which are flagellated protists that lack mitochondria and chloroplasts. These microorganisms typically inhabit anoxic environments, such as the intestines of animals, where they exist either symbiotically or as parasites, relying on fermentation for energy production. Some...

