Study of sponges reveals how nervous system and other cell types evolved to communicate
In the split second between “I’m hungry” and “Ooh, a nice salad” millions of fizzling brain cells, or neurons, meet at junctions called synapses to communicate our desires (cake), our awareness (already had cake) and our memories (what’s in the fridge?). Of course, our synapses are involved in many different types of activity, but feeding might be where it all began. In this freshwater sponge (Spongilla lacustris) – pictured using electron microscopy – scientists find synapse-like structures, even though this primitive animal doesn’t have a nervous system. Zooming inside one of its feeding chambers, we see neuron-like ‘neuroid’ cells (highlighted in purple) reaching out, using chemicals to communicate with digestive cells called choanocytes (blue, green and yellow). While researchers spot similarities with human neurons squirting neurotransmitters into synapses – and making use of similar genes – it’s perhaps not surprising that the first thoughts evolved from where the next meal is coming from.
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