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Ocean organism settles down, digests its proto-brain and loses its individuality

Last week, Science published a research report from Stanford scientists on the discovery of a single gene in a primitive marine organism that determines whether that organism recognizes wayward cells as being part of themselves or foreign. What’s interesting scientifically is that this is a very primitive immune system, and if we understand exactly how it works and how it evolved, we might learn something about how our own immune system recognizes foreign cells. It could eventually lead to new understanding about how to repel disease-causing organisms or how to successfully transplant organs.

That finding is impressive, but I also found myself fascinated by the strange organism they were studying: Botryllus schlosseri. This ocean-dwelling creature has two life stages. In the larval stage it swims about freely and has a primitive brain and notochord (like a proto-spinal cord). But eventually it attaches itself to a rock with other Botryllus organisms, dissolves its proto-brain, and buds off identical individuals to share life under a sheltering tunic. Domestic Botryllus bliss.

It gets stranger. These individual Botryllus organisms share a common circulatory system that pumps fluid through their colony. This circulating fluid carries cells from one individual to another. When two adjacent related colonies touch, they can fuse and form a joint circulatory system, allowing cells from one colony to implant themselves in the other. Circulating stem cells can then potentially replicate themselves throughout the fused colonies, replacing the cells of the recipient Botryllus until they are clones of the donor.

Luckily, they haven't become advanced enough to engage in psychotherapy. No life cycle is long enough to work out those issues.

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