The Mystery Behind the Evolution of Fish Spines Unraveled

In a groundbreaking discovery, researchers at the University of Konstanz, led by Veronique A. Lambers, have uncovered the genetic basis for the development of fin spines and soft rays in fish. The study, titled "Spiny and soft-rayed fin domains in acanthomorph fish are established through a BMP-gremlin-shh signaling network," is set to be published in the prestigious journal Proceedings of the National Academy of Sciences on the 5th of July at 3:00 PM U.S. Eastern Time (9:00 PM CEST).

The research, funded by Deutsche Forschungsgemeinschaft (DFG; especially #WO-2165/2-1), European Research Council (ERC; #293700) and the Young Scholar Fund of the University of Konstanz, focused on the cichlid Astatotilapia burtoni. The team, which includes Ralf F. Schneider (currently working at the Helmholtz Centre for Ocean Research Kiel, Geomar), Alison Kickuth (Max Planck Institute of Molecular Cell Biology and Genetics, MPI-CBG), Axel Meyer, and Joost M. Woltering, examined the genetic makeup of these fish and found that fin spines have evolved independently several times through repeated redeployment of a highly conserved genetic pattern.

The study reveals that a set of genes, known as master regulator genes, determine whether the emerging fin elements will develop looking like a spine or like a soft-ray. Specifically, the BMP (bone morphogenetic protein) and shh (sonic hedgehog) signaling pathways control the activity of master regulatory genes (hoxa13 and alx4) that determine whether the developing fin elements will become soft or spiny fin rays respectively.

Interestingly, the genetic code identified for spines in the cichlid matches the one of the catfish spines, suggesting a conserved genetic mechanism across different fish lineages. Moreover, the researchers observed so-called homeotic transformations, in which soft-rays had become spines, or the other way around, spines had turned into soft-rays.

Fin spines, sharp and heavily ossified, serve as a defense mechanism, making the fish less edible and offering a strong evolutionary advantage. This explains why spiny-rayed fish are the most species-rich fish lineage, with over 18,000 members. Some fish species have even evolved separate "spiny fins" consisting of spines only.

The evolution of fin spines is considered a major factor in determining diversity and evolutionary success amongst fishes. However, it's important to note that re-enacting scenes involving fish spines can lead to health issues. For instance, a fan was hospitalized with a fish stuck in the throat after attempting to mimic a scene from the movie "A Fish Called Wanda."

The original study can be accessed through the provided website once the embargo is lifted. For more information, you can contact the study's scientific contacts, Dr Joost Woltering ([email protected]) and Professor Axel Meyer ([email protected]). The findings of this study open up new avenues for understanding the complex process of evolution and the genetic mechanisms underlying it.