February 29, 2024

Evolution of Vertebrate Armor: How Fish Evolved Their Protective Bony Scales

A recent research study discovered that a specific type of stem cell, the trunk neural crest cell, is responsible for the development of bony protective scales (scutes) in fish. Now, using sturgeon fish, a new research study discovers that a particular population of stem cells, called trunk neural crest cells, are responsible for the development of bony scutes in fish. After a 2017 study from the University of Cambridge showed that trunk neural crest cells offer increase to dentine-based dermal armor in a type of fish called the little skate, Stundl and his colleagues hypothesized that the exact same population of cells might also offer increase to bone-based armor in vertebrates broadly.
Genetic signatures associated with osteoblast differentiation were found in the fluorescent cells in the fishs developing scutes, supplying strong evidence that the trunk neural crest cells do in fact provide increase to bone-forming cells. Combined with the 2017 findings about neural crest cells function in forming dentine-based armor, the work shows that trunk neural crest cells are certainly responsible for offering increase to the bony dermal armor that enabled the evolutionary success of vertebrate fish.

Dorsal scutes of sterlet sturgeon. A current study discovered that a particular type of stem cell, the trunk neural crest cell, is accountable for the advancement of bony protective scales (scutes) in fish. This breakthrough reveals how our soft-bodied evolutionary forefathers developed protective armor, leading the way for the advancement of a wide range of vertebrate species. Credit: Courtesy of J. Stundl
A Caltech study determined trunk neural crest cells as the origin of protective bony scales in fish, shedding light on the evolution of vertebrate armor.
About 350 million years ago, your evolutionary forefathers– and the forefathers of all contemporary vertebrates– were merely soft-bodied animals living in the oceans. In order to evolve and survive to become what we are today, these animals needed to get some security and advantage over the oceans predators, which were then dominated by shellfishes.
The advancement of dermal armor, like the sharp spines discovered on an armored catfish or the bony diamond-shaped scales, called scutes, covering a sturgeon, was an effective strategy. Thousands of species of fish utilized differing patterns of dermal armor, made up of bone and/or a compound called dentine, an important component of modern human teeth. Protective coatings like these helped vertebrates survive and progress even more into new animals and ultimately humans.
However where did this armor come from? How did our ancient underwater forefathers progress to grow this protective coat?

Now, using sturgeon fish, a brand-new study discovers that a particular population of stem cells, called trunk neural crest cells, are accountable for the advancement of bony scutes in fish. The work was carried out by Jan Stundl, now 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 study was published just recently in the journal Proceedings of the National Academy of Sciences (PNAS).
Jan Stundl holds a sturgeon fish in the lab. Credit: Courtesy of J. Stundl
Both cranial and trunk neural crest cells move from their starting points throughout the animals developing body, providing rise to the cells that make up the jaws, heart, and other essential structures. After a 2017 study from the University of Cambridge revealed that trunk neural crest cells provide rise to dentine-based dermal armor in a type of fish called the little skate, Stundl and his associates hypothesized that the very same population of cells may also give increase to bone-based armor in vertebrates broadly.
A restoration of a single sturgeon scute, close up. Bone-forming cells are marked in magenta. Credit: Courtesy of J. Stundl
To study this, Stundl and the team turned to the sturgeon fish, specifically the sterlet sturgeon (Acipenser ruthenus). Modern sturgeons, best known for their production of the worlds most expensive caviar, still have a lot of the very same characteristics as their ancestors from millions of years ago. This makes them prime candidates for evolutionary research studies.
Using sturgeon embryos grown at the Research Institute of Fish Culture and Hydrobiology in the Czech Republic, Stundl and his team used fluorescent color to track how the fishs trunk neural crest cells migrated throughout its developing body. Sturgeons start to establish their bony scutes after a number of weeks, so the scientists kept the growing fish in a dark lab in order to not interrupt the fluorescent color with light.
Hereditary signatures associated with osteoblast differentiation were discovered in the fluorescent cells in the fishs developing scutes, offering strong proof that the trunk neural crest cells do in fact provide increase to bone-forming cells. Combined with the 2017 findings about neural crest cells role in forming dentine-based armor, the work reveals that trunk neural crest cells are certainly accountable for providing increase to the bony dermal armor that made it possible for the evolutionary success of vertebrate fish.
” Working with non-model organisms is tricky; the tools that exist in standard lab organisms like mouse or zebrafish either do not work or need to be considerably adapted,” says Stundl. “Despite these challenges, information from non-model organisms like sturgeon allows us to answer fundamental evolutionary developmental biology questions in a rigorous way.”
” By studying lots of animals on the Tree of Life, we can presume what evolutionary occasions have actually occurred,” states Bronner. “This is especially effective if we can approach evolutionary questions from a developmental biology perspective, given that lots of modifications that led to varied cell types took place by means of small modifications in embryonic advancement. We were very fortunate to receive financing from Caltechs Center for Evolutionary Sciences, which helped us make research studies of this sort possible.”
Caltechs Center for Evolutionary Science (CES) is an Institute-wide, multi-division organization that recognizes and supports the examination of evolutionary modification in the natural world by means of both anthropogenic and biotic forces.
” Evolution is a central style that goes through all of biology; it combines our discipline,” says Joe Parker, Assistant Professor of Biology and Biological Engineering, Chen Scholar, and co-director of the CES. “Caltech is an amazing location with so lots of groups pursuing evolutionary issues in different contexts, consisting of at the user interface of evolution and development biology– as this study so perfectly shows.”
The paper is titled “Ancient vertebrate dermal armor developed from trunk neural crest” by Jan Stundl, Megan L. Martik, Donglei Chen, Desingu Ayyappa Raja, Roman Franěk, Anna Pospisilova, Martin Pšenička, Brian D. Metscher, Ingo Braasch, Tatjana Haitina, Robert Cerny, Per E. Ahlberg and Marianne E. Bronner, 17 July 2023, Proceedings of the National Academy of Sciences.DOI: 10.1073/ pnas.2221120120.
In addition to Bronner and Stundl, Caltech co-authors are previous postdoctoral scholar Megan Martik, now at the University of California Berkeley, and postdoctoral scholar Desingu Ayyappa Raja. Additional co-authors are Donglei Chen, Tatjana Haitina, and Per Ahlberg of Uppsala University in Uppsala, Sweden; Roman Franěk and Martin Pšenička of the University of South Bohemia in the Czech Republic; Anna Pospisilova and Robert Cerny of Charles University in Prague, Czech Republic; Brian Metscher of the University of Vienna in Austria; and Ingo Braasch of Michigan State University. Funding was provided by the European Unions Horizon 2020 research study and innovation program; the National Institutes of Health; a Wallenberg Scholarship from the Knut & & Alice Wallenberg Foundation; the Helen Hay Whitney Foundation; the Ministry of Education, Youth and Sports of the Czech Republic; the Czech Science Foundation; and the National Science Foundation.
Bronner and Parker are affiliated professor with the Tianqiao and Chrissy Chen Institute for Neuroscience at Caltech.