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Metandrocarpa taylori |
THE RACE ROCKS TAXONOMY | |
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| The common name for Metandrocarpa taylori is “colonial sea squirt”. This name comes from the animal’s ability to squeeze (“squirt”) out water if one removes them from their underwater home. Whilst they seem to be quite simple organisms regarding their shape, sea squirts are in fact quite close to humans on an evolutionary scale – they’ve got a spine. Sea squirts belong to the phylum Chordata (as shown in the table above), which includes all animals with a spinal chord, a supporting notochord (backbone), and gill slits at one point in their lives--everything from fish to humans. Tunicates have all these features as larvae. A young tunicate larvae will swim around for some time, find a rock or another hard surface to settle down and make itself stick to this surface with adhesive organs. It then starts changing, rearranges its organs (loses the tail, degrades its nervous system)and becomes a full grown sea squirt. Sea squirts possess both sex organs, but are physiologically unable to self-fertilize. Tunicates actually "wear" tunics. They secrete the leathery sac--called a tunic--that protects the animal. There are two openings in the sac, called "siphons." Cilia on the pharynx move about to create a current and draw water in through the incurrent siphon. The water is then filtered through the mucus-coated pharynx, which traps food particles. Oxygen is drawn from the water as it passes through the gill clefts, and moves out through the excurrent siphon. Divers at Race Rocks will be able to observe different kinds of sea squirts in or near rock niches. They settle down in patches of about 8-9 cm diameter. Sometimes one can also find a patch of sea squirts grown on kelp, which are mostly another species, metandrocarpa dura. Suggestions for further research: 1. How do different factors – current, sea temperature, light – influence the water circulation in the sea squirts? Which influence does this water circulation have on the sea squirt's direct environment? 2. In which depths do sea squirts grow? Does depth influence their growing? How far can the larvae move before the settle down and what influences their choice of location? Sources: http://www.umassd.edu/Public/People/Kamaral/thesis/SeaSquirts.html |
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