Researchers discover enlarged areas of the spinal cord in fish, previously found only in four-limbed vertebrates

Zebrafish at the Laboratory of Fish Biology in Nagoya University Researchers discovered that zebrafish have enlarged areas of the spinal cord, previously believed to exist only in four-limbed vertebrates.
 Photo Credit: Naoyuki Yamamoto

Four-limbed vertebrates, known as tetrapods, have two enlarged areas in their spinal cords. The two enlargements have a correlation with the forelimbs and hind limbs, respectively. These enlargements are thought to be caused by the complex muscular system and the rich sensory networks supplying nerves to the limbs.

Meanwhile, it was long thought that fish had no enlarged areas in their spinal cords due to the absence of limbs. However, a recent study by scientists from Nagoya University in Japan has revealed that zebrafish, in fact, have enlarged areas in their spinal cords, although these areas are not visible to the naked eye.

"We thought that fish also have spinal enlargements because they have paired pectoral and pelvic fins, which correspond to forelimbs and hind limbs in tetrapods, respectively," said  Naoyuki Yamamoto, a professor at Nagoya University's Graduate School of Bioagricultural Sciences and the lead author of the study.