New Insight into Repeating Body Parts Formation

Study shows shared cell populations can give rise to serially homologous structures like fins and gill arches

Apr. 2, 2026 at 6:36am

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A new study from researchers at the Marine Biological Laboratory and University of Chicago has provided important insight into how the paired fins of fishes evolved. The research shows that two different cell populations in the embryo can give rise to the same repeating structures, like the paired fins and gill arches, suggesting a developmental basis for serial homology that doesn't require one body part transforming into another over evolutionary time.

Why it matters

This finding offers a new way of thinking about serial homology, a common phenomenon in biology where structures like vertebrae or fingers show variations on a common theme. Understanding the developmental origins of these repeating body parts could shed light on how complex anatomical features evolve.

The details

The study, published in the Proceedings of the National Academy of Sciences, focused on the little skate (Leucoraja erinacea). Researcher Andrew Gillis had previously found many common genes and pathways controlling the development of the gill and fin skeletons in the skate, indicating they had common evolutionary trajectories. However, the fact that the gill arches and paired fins derive from different embryonic germ layers had been a lingering question. In a surprising 2020 study, Gillis's former postdoctoral fellow Victoria Sleight mapped the germ layers of the early skate embryo and found an overlap in the cell populations that make gills and fins. The current paper experimentally tested this finding, with first author Michael Wen transplanting neural crest cells that normally form the gill arch skeleton into a developing fin, and mesoderm cells into a developing jaw. The cells incorporated normally into the new structures, showing the cells making these body parts are equivalent and interchangeable.

  • The study was published in the Proceedings of the National Academy of Sciences in April 2026.
  • Gillis has been investigating the evolution of paired fins for nearly 20 years, since he was a PhD student with Neil Shubin at the University of Chicago.

The players

Andrew Gillis

An associate scientist at the Marine Biological Laboratory who has been studying the evolution of paired fins for nearly two decades.

Michael Wen

A University of Chicago PhD student who was the first author on the current study, carrying out the cell transplantation experiments under the co-advisement of Gillis and Victoria Prince.

Victoria Sleight

Gillis's former postdoctoral fellow who mapped the germ layers of the early skate embryo in a 2020 study, finding an overlap in the cell populations that make gills and fins.

Neil Shubin

The University of Chicago professor who was Gillis's PhD advisor when he first began investigating the evolution of paired fins.

Victoria Prince

A co-advisor to Michael Wen on the current study, along with Andrew Gillis.

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What they’re saying

“What this means is the cells making these two body parts are equivalent and interchangeable. We propose that is why the structures that form from these cells are serially homologous.”

— Andrew Gillis, Associate Scientist, Marine Biological Laboratory

“The similar response of the cells to the environment may be encoded in the genome. How similar the genomic landscapes are between cells may provide another layer to our explanation of serial homology and is something we are now investigating.”

— Michael Wen, PhD Student, University of Chicago

What’s next

Gillis's lab has moved on to other developmental investigations, but the researchers say they've made important discoveries around the question of how paired fins evolved.

The takeaway

This study provides a new developmental perspective on serial homology, showing that shared competence of different cell populations can give rise to repeating anatomical structures like fins and gill arches. This insight could help explain the evolution of other complex body parts that exhibit variations on a common theme.