Thursday, October 15, 2009

Life Photo Meme: Hostile

Kingdom: Animalia

Phylum: Cnidaria


Order: Actiniaria

Family: Actiniidae

This is a starburst anemone (Anthopleura sola), which is common in intertidal areas along the west coast. Anemones, like jellies, have stinging cells which they use to capture food and defend themselves. If you've ever touched an anemone, you've felt the sting as a sticky sensation.

In addition to the normal tentacles used to capture food, some anemones have a second set of tentacles which they inflate in the presence of other anemones. These tentacles, called acrorhagi, have larger stinging cells... larger than those found in the feeding tentacles. They will use the acrorhagi to fight with the anemones encroaching on their area.

This is complicated be the fact that some anemones with acrorhage asexually reproduce by splitting down the center. The two new anemones will not fight with each other, but will fight with any anemone that is genetically different. The anemone pictured above is solitary, and will not have any cloned neighbors, as clones from this anemone generally move away quick.

If an anemone gets beat very badly and needs a hasty retreat, they can inflate the bottom part of their body with air, and float away.

1 comment:

Wanderin' Weeta said...

That clears up a question I had. In my marine aquarium, two of my anemones (orange striped green anemone) have split, making four. I've been observing the last pair; they hang around about an inch apart, sometimes less. Another anemone that was close by suddenly disappeared (between two observations a few hours apart) when the pair moved in its direction. I've been wondering what induced it to move, and how it moved so fast. It was high on the wall, and couldn't have crept down to the bottom in the interval between observations.

Now, I've got to watch even more closely; I want to see that inflation trick!