Tiny blob - like sea creatures could oblige the keys to the origins of our nervous systems . A new subject field put placozoans under the microscope – literally – and discovered that they contain cell that look a little bit like ourneurons , something scientist have n’t experience before this far back in evolutionary time .
Placozoans have been around for about 800 million years , and as such they constitute one of the former radical of beast on the tree of sprightliness . They ’re simple critter , with a pancake - esque blobby physique and no actual organs or body parts . Each one is only about the sizing of a grain of moxie , and they live near rocks in the shallow of warm seas where they crunch away onalgaeand microorganisms .
They may not have a complex nervous system , but placozoans do have ways of controlling their behavior . They rely on specialised peptidergic cubicle that release humble protein fragment that coordinate actions like movement or feeding . A new study , direct by a team from the Centre for Genomic Regulation in Barcelona , set out to instruct more about these cells , and the evolution of these ancient animate being .
They started by create jail cell atlases for each of the four known species of placozoan , overlaying these with maps of the DNA regions that regulate different group of genes . This instance how groups of cells with different functions interact with one another . By equate these mathematical function across the different coinage , and more widely with other early animal ancestors likecomb jelliesandsponges , researcher can get a sense of how these different cellular phone types evolve .
Fourteen different types of peptidergic cellphone were discovered , and they appeared to be dissimilar from all the other cubicle types – there were no interconnect cells between them , and they shew no signal of growth or cell division .
What the researchers did find , however , was that the peptidergic cell have a striking resemblance to another cellular phone type that did n’t evolve in animals until millions of years after placozoans emerged on Earth : neurons .
“ We were astounded by the analogue , ” sound out co - first author Dr Sebastián R. Najle in astatement . “ The placozoan peptidergic cell have many similarities to primitive neuronal cells , even if they are n’t quite there yet . It ’s like bet at an evolutionary stepping stone . ”
The peptidergic cells start life in a alike way to how neurons develop , differentiating out from a universe of primogenitor cells . They have all the genetic machinery demand to build a form of rudimentarysynapse – or , at least , half a synapse . While our synapsis are the junctions at which neurons meet andexchange chemical informationto pass around brass impulses , the placozoan cells only seem able to imprint the “ sending ” end of the synapse , and not the crucial receiving end .
They also ca n’t conductelectricity , which is essential for the function of unquiet systems like ours .
But they do have a physical body of intercellular communication via chemical substance messengers called neuropeptides – not a million miles away from ourneurotransmitters .
Bringing all these observation together , it seems as though the earliest beginnings of nerve cell were shape 800 million long time ago . That ’s 150 million year before the first modern neuron , as far as we know . But as co - first author Dr Xavier Garu - Bové explained , this find is really just the commencement of a much large puzzler , affect many other retiring animal species that researchers might have been tempted to overlook until now .
“ Placozoans lack neurons , but we ’ve now found striking molecular similarity with our neural cells . Ctenophores have neuronal nets , with fundamental differences and similarities with our own . Did nerve cell evolve once and then deviate , or more than once , in parallel ? Are they a mosaic , where each piece has a different stemma ? ”
“ These are heart-to-heart interrogative that remain to be addressed . ”
The study is print in the journalCell .
