Wednesday, October 29, 2014

Crayfish or isopod?

Hi Sea Fans!

I had the opportunity to walk around the rock pools a while ago with some kids.  What fun!  When last did you go searching the rock pools for interesting little creatures?  I haven't been in a while because I've been so busy, but the memories of that visit made me want to make more of an effort to get out there.  We found all sorts of things: starfish/sea stars, anemones, mussel shells, crab moults (the outer skeleton that the crab sheds and then it develops a new outer skeleton by hardening the soft layer underneath), barnacles and even an octopus - what a treat! 

One thing that had us confused was something that looked like a baby crayfish.  The kids got so excited.  At closer inspection, we found that it was in fact an isopod.  Isopods are also crustaceans like the crab, crayfish and shrimp, and are found in virtually all marine habitats from the intertidal to the deepest oceans.  The tail-fan of the isopod is what made us think the little creature was a baby crayfish.  (Have a look at the tail-fan of the giant marine isopod below.)
Giant marine isopod that is often displayed in aquariums. (Photo:
Over 270 species occur in southern Africa.  Now isn't that amazing.  Some marine biologists study animals just to be able to classify them so that we can know which animal is which.  Sometimes there is only a very small difference between two animals, but then they are put into different categories (family, phylum, sub-phylum etc).  Fascinating stuff!

For those of you who would like to treat yourselves and see even more animals at the rock pools, find out when the next New Moon or Full Moon is.  Spring tides, which are extra high high tides and extra low low tides, occur shortly after the New Moon and Full Moon.  This is when you can see even more animals because more of the rocks will be exposed at the low tide.  Check out the following link for a cartoon explanation of spring and neap tides:

In other words, when the sun, earth and moon all line up, all the water bodies on earth (including lakes) are pulled away from the earth so that they bulge more than normal, causing the higher high tides and lower low tides that we call Spring Tides or Springs.

Enjoy discovering your rock pools Sea Fans and chat to you soon.

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