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Severed pieces of planarian behave like a whole animal
- Planarian is a free-living flatworm known for its soft, broad, leaf-shaped ciliated body and a three-branched digestive tract.[3]
- Planarian is well-known for its regeneration capabilities.
- The behaviors of freshwater planarians have been extensively studied for many years.
- Planarian behavior has been used to study the animal’s development, regeneration, molecular evolution, memory, and many more.
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- The nervous system of the planarian is one of the simplest of bilaterally symmetric animals.
- Bilateral symmetry is an animal with body shapes that are mirror images along a midline, such as a butterfly.[1]
- Planarian has an anterior brain connected to ventral nerve cords interconnected by multiple commissures.
- Commissures are nerve tissues that connect the hemispheres of the brain and the two sides of the spinal cord.[2]
- Researchers found that when an intact planarian is stimulated by mechanical means and electromagnetic radiation, the head turns, the tail contracts, and the trunk elongates.
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- When the planarian was cut into three pieces, the front of the headless middle part behaved like the head and started to turn instead of elongating.
- Additionally, the end of the head and midbody sometimes contracts instead of elongating.
- Each of the body pieces seems to behave like a whole animal.
- The results suggest that the planarian nervous system can quickly reorganize to fix functional problems complementing the slower regeneration processes.
- The reorganization allows the planarian to survive while regenerating the other tissues.
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Sources:
Le, D., Sabry, Z., Chandra, A., Kristan, W. B., 3rd, Collins, E. S., & Kristan, W. B., Jr (2021). Planarian fragments behave as whole animals. Current biology : CB, 31(22), 5111–5117.e4. https://doi.org/10.1016/j.cub.2021.09.056
