Related Experiment Video
Updated: Aug 8, 2026
04:32
Fluorescence-Activated Cell Sorting for the Isolation of Scleractinian Cell Populations
Published on: May 31, 2020
Naked corals: skeleton loss in Scleractinia
Mónica Medina1, Allen G Collins, Tori L Takaoka
1Department of Evolutionary Genomics, Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598, USA. mmedina@ucmerced.edu
Summary
Stony corals (Scleractinia) may not form a single natural group, as some are more closely related to soft-bodied corals (Corallimorpharia). This suggests stony corals lost their skeletons, with Corallimorpharia originating during the Cretaceous period.
Area of Science:
- Marine Biology
- Evolutionary Biology
- Paleontology
Background:
- Stony corals (Scleractinia) possess aragonitic skeletons, but the
- naked coral
- hypothesis questions their natural grouping.
- Previous studies showed morphological similarities and molecular data limitations in resolving scleractinian relationships.
- Discrepancies exist between fossil records and molecular estimates of scleractinian origins.
Purpose of the Study:
- To investigate the evolutionary relationships among stony corals and soft-bodied corals (Corallimorpharia).
- To test the
- naked coral
- hypothesis using complete mitochondrial genome data.
- To estimate the origin of scleractinian skeletons and Corallimorpharia.
Main Methods:
- Phylogenetic analysis using complete mitochondrial genome data from various coral lineages.
- Molecular clock dating to estimate divergence times.
- Analysis of fossil records and geological data.
Main Results:
- Mitochondrial genome data strongly support a clade of stony corals being more closely related to Corallimorpharia than to other scleractinians.
- The aragonitic skeleton likely originated between 240 and 288 million years ago (Ma) and was subsequently lost in the ancestry of Corallimorpharia.
- Corallimorpharia originated between 110 and 132 Ma during the Cretaceous, coinciding with high oceanic CO(2) levels.
Conclusions:
- The scleractinian skeleton does not define a monophyletic group, supporting the
- naked coral
- hypothesis.
- Corallimorpharia evolved from skeletonized ancestors, losing their skeletons during the Cretaceous.
- Modern stony corals face threats from increasing anthropogenic CO(2), mirroring past oceanic conditions that impacted skeletal formation.
More Related Videos
Related Concept Videos
01:12Carbon Skeletons
Life on Earth is carbon-based, as all macromolecules that make up living organisms contain carbon atoms. All organic compounds have a carbon backbone. Each carbon atom is tetravalent and can bond with four other atoms, making it an extraordinarily flexible component of biological molecules. Because carbon’s valence electrons are stable, it rarely becomes an ion. As the carbon chain increases in length, structural modifications such as ring structures, double bonds, and branching side chains...
01:21Skeleton and Calcium Homeostasis
Calcium is not only the most abundant mineral in bone but also the most abundant mineral in the human body. Calcium ions are needed for bone mineralization, tooth health, heart rate regulation and strength of contraction, blood coagulation, the contraction of smooth and skeletal muscle cells, and the regulation of nerve impulse conduction. The average calcium level in the blood is about 10 mg/dL. When the body cannot maintain this level, a person will experience hypo or hypercalcemia.
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,...
01:09Spongy Bone
All bones comprise an outer layer of compact bone, and an interior made up of spongy bone tissue, also called cancellous or trabecular bone. In long bones, spongy bone tissue is mainly found in the interior of the epiphyses (broad ends of the bone).
Spongy bone is more porous, and less dense compared to compact bone. It is composed of concentric lamellae that are arranged irregularly to form the trabecular network. In some bones, the spaces between trabeculae contain red marrow, where...
Spongy bone is more porous, and less dense compared to compact bone. It is composed of concentric lamellae that are arranged irregularly to form the trabecular network. In some bones, the spaces between trabeculae contain red marrow, where...
01:24Cells of the Epidermis
The epidermis is made of four or five layers of epithelial cells, depending on its location in the body. From deep to superficial, these layers are the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.
The cells in all these layers except the stratum basale are called keratinocytes, a type of cell that manufactures and stores the protein keratin. The keratinocytes in the stratum corneum are dead and regularly slough away, being replaced by cells from...
The cells in all these layers except the stratum basale are called keratinocytes, a type of cell that manufactures and stores the protein keratin. The keratinocytes in the stratum corneum are dead and regularly slough away, being replaced by cells from...
01:33Whole Body Regeneration
Regeneration is the process of restoring injured or lost tissues, organs, or body parts. While simpler organisms generally show greater ability to regenerate their whole body, few complex animals show similarly exceptional regeneration. For example, planarian flatworms have a unique regenerative potential making them a popular study organism among biologists to understand the mechanisms of whole body regeneration. Other organisms, such as hydra, also show extreme regeneration potential; even...