SPECIES ID / Invertebrates

Flatworms (Planarians)

• Approximately 200 freshwater species in North America

• Very high numbers usually indicate pollution from organic matter or nutrients


Identification Tips:

• Body is soft, elongated, and flattened top to bottom
• 1-20 mm long
• Slow gliding movements
• Body constricts slightly creating a distinct triangular head region
• No body segments
• One opening on bottom surface serves as mouth and anus
• 2 eyespots on head appear cross-eyed

Life History:

• Primarily predators of soft -bodied invertebrate
• Hermaphroditic
• May reproduce by dividing, or sexually depending on conditions
• Able to completely regenerate from pieces of body
• May live for many years

Very SensitiveSomewhat SensitiveFacultativeSomewhat TolerantVery Tolerant

Primary Information Source:
Voshell, J. Reese. 2002. A Guide to Common Freshwater Invertebrates of North America. McDonald and Woodward Publishing Company. Blacksburg, Virginia.