About 350 million years ago, your evolutionary ancestors—and the ancestors of all modern vertebrates—were soft-bodied animals that lived in the oceans. In order to survive and evolve to become what we are today, these animals had to gain protection and advantage over predators in the oceans, which were once dominated by crustaceans.
The evolution of dermal armor, such as the sharp spines found in armored catfish or the bony diamond-shaped scales, called scutes, that cover a sturgeon, was a successful strategy. Thousands of fish species use different patterns of dermal armor, which is made up of bone and/or a substance called dentine, an important part of modern human teeth. Protective coats like these helped vertebrates survive and evolve into new animals and eventually humans.
But where did this weapon come from? How did our ancient underwater ancestors evolve to grow this protective coat?
Now, using sturgeon fish, a new study has found that a specific population of stem cells, called trunk neural crest cells, is responsible for developing the fish’s bony scutes. The work was conducted by Jan Stundl, currently a Marie Sklodowska-Curie postdoctoral scholar in the laboratory of Marianne Bronner, the Edward B. Lewis Professor of Biology and director of the Beckman Institute at Caltech. A paper describing the research appears in the journal Proceedings of the National Academy of Sciences on July 17.
Bronner’s laboratory has long been interested in the study of neural crest cells. Found in all vertebrates including fish, chickens, and ourselves, these cells become specialized based on whether they originate in the head (cranial) or spinal cord (trunk) regions. Cranial and trunk neural crest cells migrate from their starting points throughout the developing animal’s body, giving rise to the cells that make up the jaws, heart, and other important structures.
After a 2017 study from the University of Cambridge showed that trunk neural crest cells produce dentine-based dermal armor in a type of fish called the little skate, Stundl and his colleagues hypothesized that the same that population of cells can also create bone. -based armor in vertebrates is widespread.
To study this, Stundl and the team turned to sturgeon fish, specifically the sterlet sturgeon (Acipenser ruthenus). Modern sturgeons, best known for producing the world’s most expensive caviar, share many of the same characteristics as their ancestors from millions of years ago. This makes them prime candidates for evolutionary studies.
Using sturgeon embryos grown at the Research Institute of Fish Culture and Hydrobiology in the Czech Republic, Stundl and his team used a fluorescent dye to track how the fish’s stem neural crest cells migrate throughout its body. The sturgeons begin to develop their bony scutes after a few weeks, so the researchers kept the growing fish in a dark lab so as not to interfere with the fluorescent dye in the light.
The team found fluorescently labeled trunk neural crest cells in the exact locations where sturgeon bones form. They then used another technique to stimulate the fish’s osteoblasts, a type of cell that forms bone. Genetic signatures associated with osteoblast differentiation were found in fluorescent cells in developing fish scutes, providing strong evidence that neural crest cells in the stem do indeed generate in the cells that form bone.
Combined with 2017 findings about the role of neural crest cells in the formation of dentine-based armor, the work shows that trunk neural crest cells are actually responsible for producing the bony dermal armor that has enabled evolutionary success in vertebrates. that fish.
“Working in non-model organisms is difficult; the tools available in standard lab organisms such as mouse or zebrafish do not work or have to be adjusted a lot,” said Stundl. “Despite these challenges, information from non-model organisms like the sturgeon allows us to answer fundamental questions in evolutionary biology in a rigorous way.”
“By studying many animals in the tree of life, we can determine which evolutionary events are occurring,” Bronner said. “It is especially powerful if we can approach questions of evolution from a developmental biology perspective, because many changes that lead to different cell types occur through small changes or in the development of the embryo.”
The paper is titled “Ancient vertebrate dermal armor evolved from trunk neural crest.”
Jan Stundl et al, Ancient vertebrate dermal armor evolved from the trunk neural crest, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2221120120
Provided by the California Institute of Technology
Citation: How fish evolved their bony, scaly armor (2023, July 17) retrieved on 17 July 2023 from https://phys.org/news/2023-07-fish-evolved-bony-scaly-armor .html
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