Life of the aquatic earthworm: split benthicalities
The aquatic earthworm is a fascinating benthic macroinvertebrate that reproduces asexually and sexually. Today we will explore the mystery behind the aquatic earthworm and its life as a benthic dweller. How does the aquatic earthworm reproduce asexually and sexually? To explore this question and more, we’ll start at the very beginning-- when the fertilized cocoons of aquatic earthworms are first laid.
Let’s begin by exploring asexual reproduction of aquatic earthworms. This occurs by transverse fission, a fancy term for describing the process by which the body of the benthic is split into two across it’s width. This fragmentation can occur along several parts of the body and regenerations will take place to form new aquatic earthworms. Another way asexual reproduction takes place is through budding, which occurs when new aquatic earthworms bud out of their parent’s body.
Early to mid-summer are the times when asexually reproduction is most rapidly occurring as the worms are optimizing on the mild temperature conditions and abundance of food supplies.
Sexual reproduction follows in the late summer and early fall. Aquatic Earthworms are hermaphroditic, meaning that they have the sexual parts of both male and female. Therefore cross-fertilization occurs between mating pairs in which both become fertilized. The worms will then deposit the fertilized cocoon in the debris of the stream or creek. Embryos do not experience a larval stage and transition directly into their juvenile phase throughout the span of 1 to several months depending on environmental conditions. If conditions are severe than development into a juvenile will be halted until spring whereas optimal conditions will lead to shorter development waiting times and less seasonal reproduction happening.
Because aquatic earthworms are soft-bodied organisms they are easy prey for many organisms that include fish, crustaceans, tadpoles, turtles, ducks and leeches. Alternatively, they feed on any small plant or small organic matter in streams and creeks.
Fun Fact: aquatic earthworms are scavengers, breaking down organic pollutants and making the water cleaner!
Fun Fact: most aquatic earthworms avoid bright light because they have photoreceptors all along their body surface.
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.
Wiki Commons. Retrieved from: https://northeastparkscience.wordpress.com/2010/07/19/the-way-of-the-earthworm/
Phylum Annelida. (2018). Slide Player. Retrieved from: https://slideplayer.com/slide/5260918/
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.