This would allow researchers to insert different genes into planarians and study what those genes do. Regeneration is replacing the tissue that was lost."Īt Stanford University, Hall is working to make a green fluorescent planarian - one that would be genetically engineered with a protein to glow green under a certain type of light. "It's too short of a process to have tissue replacement. "Healing is more like closing the wound and cleaning debris," Hall says. But our limbs don't grow right back if they are cut off, the way that planarians regenerate. When we suffer a severe injury, the best we can hope for is that our wounds will heal. Hall and researchers around the world are hard at work trying to understand how most of a group of flatworms called planarians can use powerful stem cells to regenerate their entire bodies, an ability humans can only dream of. "The head will just go off and do its own thing," says Hall, a doctoral student of bioengineering at Stanford University.īut within three weeks, the other pieces, as well as the head, will each have grown into a complete flatworm - identical to the one Hall sliced up - dark brown and about a half-inch long. Three of the flatworm's four pieces have started to wriggle away from each other its head is moving in circles under Hall's microscope. Tiny hairlike cilia on the underside, a thin layer of secreted mucus, and subtle muscular contractions account for their gliding movement.Nelson Hall wants you to know that the googly-eyed flatworm he just sliced into four pieces is going to be OK. During feeding, a muscular, tubelike pharynx extends out from the mouth and sucks food into the animal. There are often 2 primitive eyespots on the top surface of the head they sometimes appear “cross-eyed.” The mouth is located about midway down the underside of the body this is the only opening to the digestive tract.
Often there are 2 earlike flaps on either side of the head. Their simple nervous system is concentrated at the head end. Their bodies are bilaterally symmetrical: They have a left and right side, and what amounts to a back, a belly, and a head (that is, they are not radially symmetrical like starfish and sea anemones). In Missouri, most are tan, brown, black, or gray (but they can be brightly colored elsewhere, and species that live in caves usually look pink). There are many species, but all have some traits in common. Turbellarians, or planarians, have primitive body plans.
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