How do Flatworms survive with no blood?

February 21, 1999
From: Emily

How do organisms like the flatworm survive without blood?

jamison@pdq.net

Dear Emily,
This is a Sea Slug Site not a Flatworm site so not only am I not an expert on Flatworms. I'm afraid I would also fast run out of time if I tried to answer questions about everything.

However here's a quick answer. Flatworms don't have a separate respiratory (breathing) or circulatory (blood) system. To move all the things that our circulatory system does through their bodies (oxygen, waste gases, food and waste molecules etc) they have to rely on molecules diffusing through the body from cell to cell and through the skin. That is the reason they are so flat - their cells can't be far from the outside world from which they get their oxygen and to where they need to send their waste gases. Have a look at Wolfgang Seifarth's Flatworm Site, for more information.

Sea Slugs, like all molluscs, have a quite well developed circulatory ssytem.
Best wishes,
Bill Rudman.

Rudman, W.B., 1999 (Feb 21). Comment on How do Flatworms survive with no blood? by Emily. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/595

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