The starlet sea anemone (Nematostella vectensis) is a pro regenerator: capable of regrowing a lost body part, or even into 2 new anemones, when cut or injured.

A new study has found that the anemone remodels its whole body to do this – all to preserve its body shape.

The study is published in Developmental Cell.

“Regeneration is about restoring function after tissue loss or damage,” says senior author Aissam Ikmi, a researcher at the European Molecular Biology Laboratory in Heidelberg, Germany.

“Most research studies mainly consider patterns and sizes in regeneration, but our findings show that maintaining shape is also crucial – and it’s something the organism actively controls.”

The researchers started to look into the strange regeneration when co-lead author Stephanie Cheung noticed some odd cell divisions in a starlet sea anemone.

While just the anemone’s foot was injured, there were dividing cells around both the foot and the anemone’s mouth.

This suggests that the regeneration signals were lively across the sea creature’s whole body.

The team used a genetic analysis technique called spatial transcriptomics, alongside imagining the anemone’s cells by tagging them with fluorescent proteins, to investigate.

They found that, when injured, the anemone’s whole body responded, with reshaping occurring at long distances from the wound.

But the response was more dramatic when the injury was bigger.

The team found one group of proteins – enzymes called metalloproteases – appeared throughout the whole body as more tissue was lost.

“Metalloprotease activity has never been shown before in animals like this,” says co-lead author Petrus Steenbergen, also at the European Molecular Biology Laboratory.

What was all this remodelling for? The researchers realised it was restoring the anemone’s key shape. If a body part was removed, the anemone would become a slightly smaller version of its former self, with shape intact and body part restored.

“We were able to witness the body-wide coordination that drives this remodelling,” says Ikmi.

“This proportional response allows the anemone to restore its shape, highlighting how organisms like Nematostella interpret and respond to tissue loss in a way that’s scaled to the damage incurred.”

The researchers are planning to investigate the anemone further.

“The next big question is why maintaining shape is so important,” says Ikmi.

“And how does the organism sense its own shape? How does it know what it currently looks like?”