Life Underwater Series: Life of the Roundworm

Date: May 30, 2019 Author: EcoSpark Categories: Latest

Life of the Roundworm: the BMI cannibal

The roundworm is a fascinating benthic macroinvertebrate with a diverse and complex life that can last anywhere from two days to over a year. Today we will explore the role of roundworms in their aquatic environments. What does the roundworm prey upon to feed its energy needs?  And how do they survive in a variety of environmental conditions? To explore these questions, we’ll start at the very beginning-- when roundworm eggs are first laid.

After the male roundworm has deposited his sperm into the female, fertilization occurs in the body of the female. A thick, double-layered shell will form around each fertilized egg and these will be deposited in the aquatic environment where development will take place.

Roundworms consume invertebrates (including other roundworms), vertebrates or even plants. Roundworms that do so are parasitic and are not free-living. Free-living roundworms will feed on phytoplankton, such as diatoms, algae, bacteria and fungi. Roundworms are predatory carnivores and may have teeth for feeding, or a long spear-like structure, which is used for stabbing prey and sucking their insides. One of the most fascinating characteristics about roundworms is their ability to suspend all bodily processes, essentially living in a suspended state when food and oxygen supplies are low or unavailable. While in this ‘suspended state’, they may survive extreme climatic conditions that include droughts, deep freezes and high winds. Once conditions are favorable once again they will return to their normal functioning state.  As it grows, a roundworm will shed and replace its outer layer approximately four times.

Fun Fact: All freshwater roundworms will secrete a sticky mucous from the tip of their hind end which will allow them to anchor down to various substrates.

Fun Fact: Some species of roundworm can lay up to 200,000 eggs in a day.

Interested in learning more about benthic macroinvertebrates and how they can be used to measure the health of rivers and streams? Be sure to follow EcoSpark’s social media to stay updated on our Changing Currents program and our other citizen science and environmental education programs.


Sommer Laboratory. (2018). Worms hijack Development to foster cannibalism, study finds. Retrieved from:

Carina is an Environmental Education Assistant with the Changing Currents Program at EcoSpark. She is passionate about aquatic ecosystems and educating young minds on the connections between land and water. She recently graduated with a degree in Environmental Studies from York University and a diploma in Ecosystem Management Technology from Sir Sandford’s Fleming College, School of Environmental and Natural Resource Sciences.