Biology of free-living flatworms

Macrostomum Nervous System
Free-living flatworms, also known as turbellarians (or, unscientifically, "planarians"), are often tiny animals and only about 1 mm long and 100 µm thick, e.g. Macrostomum lignano, Isodiametra pulchra, Aphanostoma. Other acoel flatworms, e.g. Convolutriloba longifissura and Neochildia fusca, grow to a size of a couple of millimeters and are easily spotted due to their intense pigementation. Polyclad flatworms reach lengths of a few centimeters, e.g. Prosthiostomum siphunculus, Pseudostylochus intermedius, Notoplana humilis or the vividly coloured pinkish Thysanozoon brocchi. Moderately huge are some triclads in lake Baikal, which will grow half a meter in length and which feed on fish.
Free-living flatworms are creatures of the sea, creek, river, lake and soil, all around the globe.

Many turbellarians of the smaller variety live in the interstitial space, that is, between grains of sand on a beach.
Surprisingly, many sampling excursions go to nice holiday ressorts, where unsuspecting vacationists can be scared away by taking sand samples, preferably in white biohazard suits.

One of the most striking features of flatworms is their regeneration capacity, which is relying on their totipotent stem cell system.

Read more about embryonic development, postembryonic development, regeneration, stem cells, the nervous system and chromosomes of Macrostomum lignano and other flatworms at my flatworm lab site.

Contact me at:

Bernhard Egger
Department of Ultrastructural Research and Evolutionary Biology
Institute of Zoology
University of Innsbruck
Technikerstr. 25
6020 Innsbruck


Tel.: ++43 512 507 6192
Fax: ++43 512 507 2930

And remember next time you're sunbathing on the beach: there's worms beneath you. Lots of worms.
Polyclad and Macrostomum 12-cell stage
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