A sponge pushed through a cloth can assemble itself again
Separate the cells of a sponge and, left in seawater, they crawl back together and rebuild a sponge, with the cell types sorted into the right layers.
In 1907 Henry Van Peters Wilson squeezed living sponges through fine cloth, so that the tissue came apart into cells and small clusters. The cells settled, moved, stuck, and over days organised into a functional sponge again: an outer layer, inner chambers, the right cells in the right places. Mix two species and, in the classic experiments, they sort rather than fuse into a hybrid. Recognition is on the cell surface. The animal is a society that can adjourn and reconvene.
It is not immortality and not 'you can do this to anything.' Many animals die when you dissociate them, because their cells cannot find the pattern again. A sponge's pattern is simple enough, and its cells adhesive enough, that the pattern is in the parts. Later work used the same trick to study how cells stick. The original observation still has the force it had: take the animal completely apart, and the animal comes back, from no instructions except the ones each cell was already carrying.
Caveats
- Success depends on the species, the health of the cells, and the violence of the separation. It is a real laboratory result, not a promise that any torn sponge on a beach will heal into one.
- The rebuilt sponge is a new organisation of the old cells. It is not proof that the original individual, as a continuous life, was unharmed.
Sources
- 1Wilson H. V.. On some phenomena of coalescence and regeneration in sponges. Journal of Experimental Zoology 5, 1907.