Sunday, October 5, 2014

Planeria

Water quality testing of Cedar Creek, in Allen County, is always an interesting and enjoyable activity. This past Saturday we found an abundant variety of aquatic invertebrates while testing the chemical and biological properties of the creek at Metea County Park. Among the various mayfly, dragonfly, caddisfly, and damselfly nymphs we found several little non-parasitic flat worms known as Planaria (Planaria dorotocephala).  Planaria are solid bodied flat worms that have the unique ability to regenerate a complete worm if cut into smaller pieces.  A planaria that is cut longitudinally down the center line will generate two complete individuals.  When cut transversely each segment will regenerate a new individual. Planaria are very near the bottom of the food chain and feed on very small organisms or dead animal matter.  They move by means of cilia (small hairs) and a slime layer on their bottom surface and are not easy to photograph as they slime across a petri dish.

The eye-spots (ocelli) are light sensing organs which help the planaria to move away from light.
Being somewhat intolerant of pollution planaria are good indicators of water quality and are normally found in oxygenated rapidly moving streams.
Photos by J. Ormiston