Lampreys seem like one thing out of a horror film, with their sucky mouths chock full of tooth, eel-like our bodies, and parasitic behaviors. These “water vampires” signify a bit of an evolutionary fork in the street between vertebrates and invertebrates, and the scientific debate about simply how intently associated we’re to these carnivorous fish has taken yet one more flip.
Scientists discovered some proof that lampreys have a rudimentary sympathetic nervous system–which is believed to management the fight-or-flight response in vertebrates. The findings are detailed in a examine printed April 17 in the journal Nature and will immediate a rethink of the origins of the sympathetic nervous system.
Lampreys are the closest dwelling organisms scientists have to learning the fish ancestors that vertebrates developed from some 550 million years in the past. They belong to an historic vertebrate lineage referred to as Agnatha–or jawless fish. Some scientists imagine that they signify the earliest group of vertebrates that’s nonetheless dwelling and may give us an evolutionary window into all vertebrate ancestors. Other scientists query the theories due to an absence of lamprey proof in the fossil file.
[Related: Giant prehistoric lamprey likely sucked blood—and ate flesh.]
Scientists beforehand believed that lampreys didn’t have sympathetic neurons. These neurons are half of the sympathetic nervous system, a system of nerves that focus on the inside organs all through the physique together with the intestine, pancreas, and coronary heart. The system works collectively to reply to harmful or aggravating conditions. It additionally helps an organism’s physique keep homeostasis, ensuring that the coronary heart retains pumping, the digestive system retains transferring, and extra.
In this new examine, a group used lampreys to take a look at how developmental adjustments could have promoted the evolution of vertebrate traits like fight-or-flight. They discovered proof of the sorts of stem cells that ultimately kind sympathetic neurons. The presence of these cells in lampreys might revise the timeline of when the sympathetic nervous system started to evolve.
“Over a hundred years of literature has suggested that lamprey lack a sympathetic nervous system,” examine co-author and California Institute of Technology biologist Marianne Bronner stated in an announcement. “Surprisingly, we found that sympathetic neurons do, in fact, exist in lamprey but arise at a much later time in lamprey development than expected.”
Bronner and her group studied neural crest cells. These are a sort of stem cells which are particular to vertebrates and provides rise to the a number of cell sorts discovered all through the physique. Scientists beforehand believed that lampreys lacked the neural crest-derived precursors, or progenitors, that in the end construct the sympathetic nervous system.
According to Bronner, researchers beforehand regarded for proof of a sympathetic nervous system too early in lamprey improvement in contrast to different animals. For instance, the sympathetic nervous system varieties in the first two to three days of improvement in birds.
[Related: You might have more in common with the sea lamprey than you realize.]
Study co-author and Cal Tech evolutionary biologist Brittany Edens checked out the neural crest–derived progenitor cells in lampreys that in the end give rise to sympathetic neurons. She discovered that in lampreys, the neural crest–derived progenitors seem a lot later than different animals. They can seem so long as one month after fertilization. The cells additionally don’t totally mature into neurons till about 4 months of improvement, throughout the fish’s larval stage.
It continues to be not identified whether or not the sympathetic nervous system of lampreys controls fight-or-flight-like behaviors comparable to different vertebrates. According to the group, these findings recommend that the developmental program that controls the formation of sympathetic neurons stays throughout all vertebrates, from lamprey to mammals.