This account of how different sea anemone colonies battle for space in tide-pools while the tide is out is amazing — real red-in-tooth-and-claw stuff. They even differentiate into distinct castes: "warriors, scouts, reproductives."
When the tide is out, the polyps are contracted and quiet. As the tide covers the colonies, "scouts" move out into the border to look for empty space to occupy. Larger, well-armed "warriors" inflate their stinging arms and swing them around. Towards the center of the colony, poorly armed "reproductive" anemones stay out of the fray and conduct the clone's business of breeding.
When anemones from opposing colonies come in contact, they usually fight. But after about 20 or 30 minutes of battle the clones settle down to a truce until the next high tide.
It's not just polyps along the border between two clones that clash. Polyps three or four rows away from the front will reach over their comrades to engage in fights, Grosberg said.
Differentiation into warriors seems to depend on a combination of signals from enemy stings and the genetics of the colony. Different colonies react differently to similar signals, explaining why different clones are organized into so many different kinds of armies. But borders between colonies can remain stable for years, even though the two colonies organize their armies in different ways.
(Thanks, Nick!)
