Ctenophores, or comb jellies, are unusual jelly-like animals that ghost by the ocean propelled by tiny hairs referred to as cilia. They’re an enigmatic bunch, with origins that stretch again roughly 540 million years, and nobody is bound precisely after they diverged from the remainder of the tree of life.
Now, researchers have found that these alien-like creatures are even weirder than we thought: Their nervous system is like nothing ever seen earlier than. As an alternative of counting on gaps between nerve cells referred to as synapses for communication, not less than a part of the ctenophore nervous system is fused.
“We’ve not really seen this in another animal earlier than,” research co-author
Maike Kittelmann (opens in new tab), a cell and developmental biologist at Oxford Brookes College within the U.Ok., advised Reside Science. “It signifies that there are different ways in which neurons can join to one another.” Nervous system evolution
The invention raises questions on how all nervous methods advanced and provides gasoline to a long-standing debate about how comb jellies are associated to the remainder of the animal kingdom. Many scientists thought that the nervous system in animals advanced solely as soon as, sooner or later after sponges broke off from the remainder of the animal kingdom, as sponges do not need a nervous system. However some scientists assume ctenophores diverged from different animals early and advanced their very own nervous system individually.
Associated: What is the weirdest sea creature ever found?
Comb jellies do not have brains, however have a weblike system of neurons often called the nerve internet. It is inside this nerve internet that researchers discovered the fused neurons. The unusual fused association might trace that these methods advanced independently, Kittlemann mentioned. Nevertheless it’s nonetheless an open query.
“We don’t actually know for positive,” she mentioned.
The brand new analysis, printed April 20 within the journal
Science (opens in new tab), appears to be like at ctenophores in an early developmental stage, after they’re only a few days previous. At this stage, ctenophores can transfer round freely and even reproduce, however they don’t seem to be full adults. (Relying on species, ctenophores have life spans between a few month and a number of other years.)
The overwhelming majority of nerve cells in animals talk by way of synapses, that are gaps between cells. To “speak,” neurons launch chemical substances referred to as neurotransmitters throughout these gaps. However the brand new research discovered that throughout the ctenophore nerve internet, the cells are fused and their membranes linked in order that the trail from cell physique to cell physique is steady. This construction known as a syncytium.
“There are another animals which present fused neurons however to not that excessive, the place you could have a complete nerve internet,” research co-author
Pawel Burkhardt (opens in new tab), who research the evolutionary origin of neurons and synapses at Norway’s College of Bergen, advised Reside Science. Fused neural networks
The invention raises a complete bevy of recent questions, Burkhardt mentioned, from how this fused community develops to the way it capabilities. The identical cells which might be fused collectively additionally make connections to different nerve cells by way of synapses, and different components of the ctenophore nervous system use synapses, too. It is not clear, Burkhardt mentioned, why comb jellies use two totally different strategies of communication between their nerve cells.
One chance is that the fused nervous system has some benefit for tissue restore and therapeutic,
Leslie Babonis (opens in new tab), an evolutionary biologist at Cornell College who was not concerned within the new research, advised Reside Science. Ctenophores are able to regenerating a completely new animal from a small chunk of flesh.
“Possibly this is likely one of the secrets and techniques to their unbelievable skill for regeneration,” Babonis mentioned.
The analysis staff solely checked out one species of ctenophore —
Mnemiopsis leidyi — in a single developmental stage, in order that they now plan to search out out whether or not different species have fused neural networks and whether or not this fusion persists by the animal’s entire lifespan.
This might assist reply questions concerning the evolution of the nervous system and whether or not it arose as soon as, twice or extra instances. If many ctenophores have distinctive fused nervous methods, this might lend credence to the speculation that ctenophores advanced their nervous system individually from different animals. Nevertheless it’s additionally potential that every one animal nervous methods nonetheless share a standard origin, and ctenophores advanced the fusion later, the researchers mentioned.
Solely a handful of lineages within the animal kingdom have had their nervous methods intently studied,
Leonid Moroz (opens in new tab), a biologist on the Whitney Laboratory for Marine Biosciences on the College of Florida, advised Reside Science. Moroz was not concerned within the present research however led a 2014 research (opens in new tab) of ctenophores, which discovered that the genetic and chemical foundation of the ctenophore neural system is kind of totally different from that seen in different animals.
If the nervous system is a poem, Moroz mentioned, ctenophores use a unique alphabet from the remainder of the animal kingdom to put in writing theirs. He argues that these jellies advanced their nervous system independently, and that different understudied animals could have achieved the identical. Unraveling this variety might result in a deeper understanding of how neurological issues come up.
“We have to perceive syntax, we have to perceive grammar,” Moroz mentioned. “However we can not do it with just one or few species.”