Monday, March 12, 2018

Decorator colours

The plumose anemone in my tank has a brown column and  beige tentacles, a common combination. Often, though, they are white on white; a white column, and whiter tentacles. I had never seen one with a green head before.

Plumose anemone, Metridium senile in the tidepool under the glacial erratic. With green tentacles.

I browsed images on Google; I found a few white "Mets" with pale green tentacles, always in photos taken during a dive. This one is in a few inches of water. And that was the colour as my eyes saw it; I used the flash, because the anemone was in shade, but those tentacles were a definite blue-green.

Another. This one has white tentacles, but the base is a pale blue.

This one matches the one in my tank. Some of the red blotches around it are tubeworm "flowers".

Another "normal" M. senile.

Deep under the rock, starfish wait out the dry spell. The flat, spread out anemone seems to be a burrowing anemone, with its mouth exposed. Must have just eaten something. Maybe one of those little fish?

More vivid colours. A deep pink tubeworm, still fishing while the water lasts. The pink-tipped green anemones below have shut down for now.

Even the hermit crabs are wearing party colours. I spotted this one with those bright blue pincers, like the one I brought home last week.

Three hermits, a dead kelp crab,and limpets. The deep red  critters at bottom right are not fish; they're shreds of seaweed.

Kelp crabs are usually a dull olive green, sometimes greenish brown. I don't know if this one was joining the explosion of colour in his lifetime, or if there's some sort of blue-green algae that took over his carapace and legs after he died.

This photo was taken aiming straight down into a foot-deep rounded hole. There are many of these near the bottom of the intertidal zone; circular holes, smooth-walled, looking like someone at some time removed a bowling ball from the rock. What causes this? I don't know.

I am always on the lookout for nice whelk shells for my hermits at home. Here, around this erratic, there are many whelks, all healthy and shiny, but no empty shells. And almost every hermit crab I saw was wearing a smashed and broken shell. What happened to the fresh shells?

I feel sorry for these hermits; the ones I brought home were quick to switch into intact shells; they do know the difference. I almost feel like collecting some decent shells from my tank and spreading them around this tide pool. Or would the tide immediately haul them off and slam them against the rocks until they were full of holes?

Questions, questions.


  1. For most animals, the availability of food is what limits their population. Interestingly, it is the symbiotic relationship with a snail, and the distribution of empty shells by the surf that probably controls hermit population.

  2. Yes, it hadn't occurred to me before; I took suitable empty shells to be plentiful. Seems not, at least not here. And a hermit in a broken shell, with his rear end hanging out is so vulnerable!

  3. Your tank must give you hours of pleasure. How large is it? - Margy

    1. It's a mid-size small aquarium, only 10 gallons. But since my beasties are almost all tiny, it's adequate.


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