Blue planarian flatworm fact sheet | Field of Mars EEC
What are blue planarian flatworms?
Blue planarian flatworms are native Australian land flatworms. Their scientific name is Caenoplana coerulea. They are also called blue planarians or blue garden flatworms.
They have a long, soft, flat body and usually live in damp places such as leaf litter, soil, rotting logs and well-treed gardens. Unlike earthworms, blue planarian flatworms do not have a segmented body. They glide slowly on mucus and hunt small animals in the leaf litter.
Fast facts – Blue planarian flatworms
Scientific name – Caenoplana coerulea
Scientific group – Blue planarian flatworms are land flatworms in the family Geoplanidae. They belong to the flatworm phylum Platyhelminthes.
Body features – They have a long, soft, flat body, a narrow head, many tiny eyespots, a pale stripe along the back and a mouth on the underside of the body.
Diet – Blue planarian flatworms are carnivores. They eat small soil and leaf litter animals such as slaters, millipedes, earwigs and some snails.
Habitat – Blue planarian flatworms live in damp leaf litter, soil, rotting logs, under rocks and in well-treed gardens. They are often seen after rain.
Life cycle – Blue planarian flatworms hatch from egg capsules as tiny flatworms. They grow into juveniles and then adults.
Special feature – Blue planarian flatworms glide on mucus. Their mucus helps them move, protects their soft body and can help trap prey.
What do blue planarian flatworms look like?
Blue planarian flatworms are usually dark blue, blue-green, navy or almost black on top. A thin pale stripe runs along the middle of the back. The underside is usually a brighter or paler blue, which gives the species its common name.
The head end can look pink, reddish or pale. Blue planarian flatworms also have many tiny eyespots. These eyespots do not see detailed pictures like human eyes, but they help the flatworm detect light and dark.
Where do blue planarian flatworms live?
Blue planarian flatworms live in moist forests, rainforest edges, bushland and well-treed gardens in eastern Australia. They shelter in damp microhabitats under rocks, logs, bark, leaf litter and plant pots.
At Field of Mars Reserve, animals like blue planarian flatworms are most likely to be found in damp, shady places with leaf litter, fallen bark, rotting wood and soil. They are most often noticed after rain, when the ground is damp enough for them to move without drying out.
What do blue planarian flatworms eat?
Blue planarian flatworms are predators. They hunt small invertebrates that live in soil and leaf litter, including slaters, millipedes, earwigs and some land snails.
They use sticky mucus to help catch prey. Their mouth is on the underside of the body, not at the head end. Food enters through this opening, and waste leaves through the same opening.
What is the life cycle of a blue planarian flatworm?
Blue planarian flatworms hatch from small egg capsules. Young flatworms look like tiny versions of the adults. They do not change through a caterpillar or pupa stage like butterflies, beetles and many other insects.
As they grow, young flatworms feed on small invertebrates and stay hidden in damp places. Adult flatworms are hermaphrodites, which means each animal has both male and female reproductive organs.
What adaptations do blue planarian flatworms have to help them survive?
Blue planarian flatworms have several adaptations that help them survive in damp habitats. Their flat body helps them slide into narrow spaces under bark, logs, rocks and leaf litter. Their mucus helps them glide over surfaces and reduces water loss from their soft body.
Their many eyespots help them detect light, so they can avoid bright, dry places. Their dark colour helps them blend in with wet soil, bark and leaf litter. Their sticky mucus can also help trap small prey animals.
Why are blue planarian flatworms important?
Blue planarian flatworms are part of the hidden leaf litter food web. They help control some small invertebrates and are one of many predators living in damp soil and leaf litter.
Their presence can suggest that a habitat has moist, sheltered places for small animals. Leaf litter, fallen bark, rotting logs and soil are important homes for many invertebrates, including slaters, millipedes, beetles, snails, spiders and flatworms.
How can you help blue planarian flatworms?
You can help blue planarian flatworms by protecting damp, shady habitat. Leave leaf litter, fallen bark and rotting logs in bushland where they are safe to remain. These natural materials provide shelter for flatworms and for the small animals they eat.
Avoid unnecessary pesticide use in gardens and outdoor learning areas. If you find a blue planarian flatworm, observe it carefully and leave it where it is. Do not handle, collect, cut or move it. After looking under rocks or logs, gently return the shelter to the way you found it.
Related fact sheets
More invertebrate fact sheets
- Invertebrate fact sheets – explore more animals without backbones that live in bushland, soil, leaf litter and water.
- Leopard slug fact sheet – compare blue planarian flatworms with slugs, another soft-bodied animal that moves using mucus.
- Common rough slater fact sheet – learn about a damp leaf litter animal that blue planarian flatworms may hunt.
- Termite fact sheet – learn about another invertebrate that lives in soil, wood and leaf litter habitats.
- Beetle fact sheet – discover more insects that live in leaf litter, under bark and in rotting wood.
Habitats and ecosystems
- Leaf litter habitats fact sheet
- Eucalypt forest fact sheet – explains the local bushland context.
- Field of Mars Reserve fact sheet – explains the local reserve and habitat diversity.
Attributions
References
Australian Museum. Planarian Worms. [online] Available at: https://australian.museum/blog-archive/at-the-museum/planarian-worms/
James Cook University. Caenoplana coerulea (Blue garden flatworm). [online] Available at: https://www.jcu.edu.au/discover-nature-at-jcu/animals/miscellaneous-fauna/caenoplana-coerulea
NatureMapr. Caenoplana coerulea (Blue Planarian, Blue Garden Flatworm). [online] Available at: https://canberra.naturemapr.org/species/2053
Luis-Negrete, L.H., Brusa, F. and Winsor, L. The blue land planarian Caenoplana coerulea, an invader in Argentina. [online] Available at: https://www.scielo.org.mx/scielo.php?pid=S1870-34532011000100026&script=sci_arttext
Terrace, T.E. and Baker, G.H. The Blue Land Planarian, Caenoplana coerulea Moseley (Tricladida: Geoplanidae), a predator of Ommatoiulus moreleti (Lucas) (Diplopoda: Julidae). [online] Available at: https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1440-6055.1994.tb01250.x
Royal Horticultural Society. Non-native flatworms: what gardeners should know. [online] Available at: https://www.rhs.org.uk/biodiversity/non-native-flatworms
Image attributions
A blue planarian flatworm – Field of Mars EEC (original illustration).
Blue planarian flatworms are long, flat and smooth – “File:Caenoplana coerulea Victoria 2.jpg” by Nicole Kearney. CC BY 4.0. Available at: https://commons.wikimedia.org/wiki/File:Caenoplana_coerulea_Victoria_2.jpg
The head end of a blue planarian flatworm can be pinkish or reddish – “File:Blue garden flatworm (8254115530).jpg” by John Tann. CC BY 2.0. Available at: https://commons.wikimedia.org/wiki/File:Blue_garden_flatworm_(8254115530).jpg
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Blue planarian flatworms live in damp, shady places with leaf litter, fallen bark and rotting wood – Field of Mars EEC (original image).
Millipedes are one type of small invertebrate found in damp leaf litter habitats – “File:Heterocladosoma bifalcatum, Red Legged Millipede, Sydney.jpg” by Stu’s Images. CC BY-SA 4.0. Available at: https://commons.wikimedia.org/wiki/File:Heterocladosoma_bifalcatum,_Red_Legged_Millipede,_Sydney.jpg
Slaters live in damp places and may be eaten by blue planarian flatworms – “File:Porcellio scaber DC1b.jpg” by Macleay Grass Man. CC BY 2.0. Available at: https://commons.wikimedia.org/wiki/File:Porcellio_scaber_DC1b.jpg
A related land flatworm egg cocoon with newly hatched young flatworms – “File:Obama nungara Justine et al PeerJ 2020 fig-10-full.png” by Jean-Lou Justine, Leigh Winsor, Delphine Gey, Pierre Gros and Jessica Thévenot. Creative Commons Attribution-Share Alike 4.0 International. Available at: https://commons.wikimedia.org/wiki/File:Obama_nungara_Justine_et_al_PeerJ_2020_fig-10-full.png
A flat body and mucus help blue planarian flatworms move through damp shelters – “File:Caenoplana coerulea blue underneath.JPG” by Poyt448 / Peter Woodard. Public domain. Available at: https://commons.wikimedia.org/wiki/File:Caenoplana_coerulea_blue_underneath.JPG
Blue planarian flatworms are part of the leaf litter food web – “File:Caenoplana coerulea Victoria 3.jpg” by Nicole Kearney. CC BY 4.0. Available at: https://commons.wikimedia.org/wiki/File:Caenoplana_coerulea_Victoria_3.jpg
Leave blue planarian flatworms where you find them – “File:Blue garden flatworm (8253041759).jpg” by John Tann. CC BY 2.0. Available at: https://commons.wikimedia.org/wiki/File:Blue_garden_flatworm_(8253041759).jpg
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