Why does planaria have bilateral symmetry

This suggests that a bilateral body plan may have evolved earlier than previously thought , read more. Some flatworms use the mitochondria in some cells which we all have in their heads to form lenses to focus light onto their light sensitive cells. Read the article on Creature Cast. Planarians can regenerate body parts including growing a new head and brain. When scientists studied the process identified the gene that makes this possible and that the planarians have stem cells to make these new body parts.

Read more. Scientists are investigating how planarians maintain the stem cells that let them regenerate. Learn more. Invasive flatworms can cause major disruptions to ecosystems : read about an invasive flatworm on the Shape of Life website. Researchers at the University of New Hampshire found that flatworms in estuaries can indicate the health of the ecosystem.

Flatworms play a role in many food chains. Read about some of them. Parasitic flatworms can disrupt ecosystems. Some flatworms, planaria, can be used as models for toxicology Platyhelminthes from the Florida Museum of Natural History.

The Marine Flatworm Galleries. Skip to main content. The eye spots are sensitive to light. Planarians move away from the light and are most active in the dark. Second, light and water current can be used demonstrate kinesis change of speed and taxis change of direction.

Planarians are also sensitive to shock. Therefore, planarians can be conditioned with several stimuli and responses. The brain of these free-living flatworms is a bilobed structure with a cortex of nerve cells and a core of nerve fibres including some that decussate to form commissures. Special sensory input from chemoreceptors, photoreceptor cells of primitive eyes, and tactile receptors are integrated to provide motor responses of the entire body, and local reflexes.

Many morphological, electrophysiological, and pharmacological features of planarian neurons, as well as synaptic organization, are reminiscent of the vertebrate brain.