How The Pufferfish Got Its Spines

An international team of biologists has found that homologs of genes involved in hair and feather formation in other vertebrates are responsible for pufferfish spine development.

AsianScientist (Aug. 21, 2019) – Scientists in Japan and the US have identified the molecular pathways that regulate spine development in pufferfish. They published their work in the journal iScience.

Pufferfish are known for their strange and extreme skin ornaments, but how they came to possess the spiky skin structures known as spines has largely remained a mystery. As it turns out, the biological mechanism is pretty similar to how other vertebrates get their hair or feathers—and might have allowed the pufferfish to fill unique ecological niches, said Assistant Professor Gareth Fraser at the University of Florida, US, corresponding author of the paper.

“Pufferfish are some of the strangest fish in the ocean, particularly because they have a reduced skeleton, beak-like dentition and they form spines instead of scales—not everywhere, but just in certain patches around the body,” said Fraser.

The team first followed the development of pufferfish spines in embryos. While they had initially hypothesized that the spines formed from scales—that the pufferfish lost its scale component but retained the spine—they found that the spines are developmentally unique from scales. They also reported that the development of pufferfish spines relies on the same network of genes that are commonly expressed in the feathers and hairs of other vertebrate animals.

“It just blows me away that regardless of how evolutionarily different skin structures in animals are, they still use the same collection of genes during development,” Fraser quipped.

The researchers then decided to look at what would happen if they manipulated those genes. Using CRISPR-Cas9 and other gene editing techniques, they blocked specific genes that are classic markers of skin appendage development. Doing so allowed them to reduce the number of spines on pufferfish, as well as loosen the restriction on where the spines appear.

Normally, the spines are localized to specific areas on the pufferfish. Fraser noted that this localization is to enhance protection.

“When pufferfish inflate by ingesting water or in some cases air, their skin becomes stretched, especially around the abdomen, and is more susceptible to damage, such as being torn,” he said. “Spines reinforce the puffed-up abdomen. In extreme cases, some pufferfish have lost all other spines on their body and retain only the abdominal spines.”

Fraser added that shifts in spine coverage and morphology may allow pufferfish to take advantage of new ecological niches that are available to them. As the climate changes and environments become different, pufferfish may use these evolving traits to tolerate and adapt to change, he said.

Through their sequencing efforts, the researchers hope to ultimately identify the differences in the genome that allow for diversity in spine coverage and morphology, as well as gain a deeper understanding of the transition from scales to spines.

The article can be found at: Shono et al. (2019) Evolution and Developmental Diversity of Skin Spines in Pufferfishes.


Source: Cell Press; Photo: Gareth Fraser/iScience.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Asian Scientist Magazine is an award-winning science and technology magazine that highlights R&D news stories from Asia to a global audience. The magazine is published by Singapore-headquartered Wildtype Media Group.

Related Stories from Asian Scientist