According tomedia New Atlas, the arches of fish and pairs of fins have a similar bone structure — so much so that it was once thought that fins evolved from arches. Although this theory was later rejected, a new study suggests that it may be right.
First, “pairing” simply means having a matching set of fins, such as the pectoral fins located at the front of the fish. A bow is a curved bone or cartilage, each of which supports an actual crust. As early as the end of the 19th century, German anatomist Karl Gegenbaur speculated that pairs of fins evolved from arches, which appeared earlier in the fossil record than fins.
In the years that followed, this theory was widely questioned. In fish embryos, the two body parts are developed from two different groups of cells — fins from the mid-embryo cells and arches from nerve cells, the scientists said.
However, a new study suggests that Gegenbaur may have always been right. Dr Andrew Gillis, from the University of Cambridge, and Dr Victoria Sleight, now from the University of Aberdeen, led the study.
The scientists first injected fluorescent dye traces into the nerve crucible and mid-embryo cells of the mackerel embryo, and then tracked which bone regions those cells contributed over the next few weeks. It was found that the paired fins were formed entirely by the embryo cells, and the cartilage jaw and the first arch were formed entirely by nerve cells, but the remaining fish arches were formed by a mixture of two cell types.
“It has long been thought that the similarities between fish’s gills and fin skeletons are just coincidences, ” Gillis said. “We found that these structures developed from a common pool of cells, suggesting that this is not the case — the gills and fins have a deeper, more substantial evolutionary relationship, which is reflected in their embryonic development.”
The study was described in a recent paper published in the journal eLife.