Fish developed their spines through the process of evolution, which involved the development of vertebrae in their backbones around 500 million years ago, making them the first vertebrates to develop such a feature.

In a groundbreaking study, researchers from the University of Konstanz have revealed how fin spines arise during the embryonic development of fish. The findings, published in the Proceedings of the National Academy of Sciences (PNAS), provide insights into the genetic mechanisms behind the formation of fin spines, a feature that offers a significant evolutionary advantage for many species.

The study, titled "Spiny and soft-rayed fin domains in acanthomorph fish are established through a BMP-gremlin-shh signaling network," focuses on the cichlid Astatotilapia burtoni, a model species for the spiny-rayed fish. The research team, led by Dr Joost Woltering and Professor Axel Meyer, discovered that the BMP (bone morphogenetic protein) and shh (sonic hedgehog) signaling pathways are crucially involved in the formation of the fin pattern of fish during development.

The researchers found that these master regulator genes determine whether emerging fin elements will develop as spines or soft-rays. Modulation of the BMP signaling resulted in changes in the activation of master regulatory genes and homeotic transformations, where soft-rays became spines or vice versa.

The study also shed light on the genetic code that determines the location of spines in the cichlid fins. Interestingly, this genetic code is also active in fins that do not have spines, suggesting a deeply conserved patterning system that may have been redeployed during evolution.

The findings suggest that fin spines have evolved independently several times through repeated redeployment of a highly conserved genetic pattern. The team's future research will focus on the genes downstream of the identified spine and soft-ray control genes to understand how they alter fin morphology through controlling ossification and cellular growth pathways.

The study was funded by the Deutsche Forschungsgemeinschaft (DFG; especially #WO-2165/2-1), European Research Council (ERC; #293700) and Young Scholar Fund of the University of Konstanz. The embargo on the study will lift on the 5th of July 2021 at 3:00 PM U.S. Eastern Time (9:00 PM CEST).

A photo of the cichlid fish Astatotilapia burtoni, the model organism used in the study, can be downloaded from this link: https://cms.uni-konstanz.de/fileadmin/pi/fileserver/2021/how_fish.jpg. For media inquiries, please contact the University of Konstanz Communications and Marketing at + 49 7531 88-3603 or [email protected].

In addition to Dr Woltering and Professor Meyer, the research team includes Armin N. Brand and researchers who have worked with the zebrafish (Danio rerio). The original study is published in PNAS with the DOI: 10.1073/pnas.2101783118.

Fish developed their spines through the process of evolution, which involved the development of vertebrae in their backbones around 500 million years ago, making them the first vertebrates to develop such a feature.