Fab four Phyla part two: Cnidarians

A large christmas anemone with its tentacles partially exposed to air.

Cnidarians are named after the venomous cells that distinguish them, called cnidocytes.  Cnidocytes release their poison through an organelle within the cell called a cnidocyst or nematocyst.  These stings vary greatly in severity with some being easily strong enough to kill a person while others would hardly be noticed.  Cnidarians include animals like anenomes and sea jellies with both having jelly like bodies, a hollow gut, tentacles and stinging cells. Fortunately, the cnidarians found around here are not dangerous.  We occasionally have a Lion's Mane jelly wash up on shore which could give you a nasty sting, but nothing fatal.

Burrowing anemones

A burrowing anemone colored green by a symbiotic algae

While tidepooling, anenomes are the most common cnidarian encountered though often times people won't recognize them; anemones, being 90% water, look like formless blobs when the tide goes out.  The best place to see an anemone with all its tentacles out is in a tide pool or hanging off the side of a dock.  Anemones are always great fun to introduce to a group.  We encourage people to "shake hands" with an anemone by touching its tentacles.  The anemones here aren't powerful enough to give a painful sting but you can definitely feel the effects of the harpoon like nematocysts firing into your finger.  The nematocysts are like a spring loaded trap; they are set off by anything brushing against them.   Our anemone's nematocysts are weak enough that it only feels as if the tentacles have a strong adhesive on them which is a lot of fun to show to the groups.  The truly bold can give the anemones a kiss; because the skin on your lips is thinner and more sensitive than on your fingers you will actually feel a little bit of a sting.

Orange colonial anemones about the size of a fingernail

One of the reasons we don't have the extraordinarily poisonous animals often found in more tropical waters is food.  Places like the Caribbean with its vast expanses of sand, warm water and beautiful reefs are more like deserts.  Colder water nearer to the poles is able to hold much more dissolved oxygen which allows it to support more life.  During the summer months, when the days are nearly endless, phytoplankton (plankton that uses photosynthesis) flourish, providing a source of food for practically everything else in the ocean.  Because food is so abundant here, animals are not as concerned with protecting themselves or hunting with expensive (in terms of resources) toxins.  They would rather put their energy towards reproduction and growth.  Where prey is scarcer animals need to spend more resources to protect themselves and to ensure that if they inject something with their poison they will get a return on that expenditure.  They can't afford to let an animal escape since something might not come along later.  In Alaskan waters, there is so much food to go around that many animals can afford to wait, they know they'll  have a shot at something sooner or later.