Elliptio complanata – a familiar mollusc

Georgian Bay Forever is working with Dr. Kevin McCann of the University of Guelph, and the Canadian Centre for DNA Barcoding to catalogue all the aquatic organisms in Georgian Bay. This will help with measuring the impact of environmental stressors like climate change and human activity such as shoreline development as well as aiding in future conservation efforts, ecosystem monitoring, forensics, and tracking invasives. All the specimens collected and identified will also contribute to the International Barcode of Life , a multi-nation effort to catalogue the world's biodiversity. Here is one example from Georgian Bay's Aquatic Species Library.


    Kingdom: Animalia
    Phylum: Mollusca
    Class: Bivalvia
    Order: Unionoida
    Family: Unionidae
    Subfamily: Ambleminae
    Genus: Elliptio
    Species: Elliptio complanata

Identification - Linnaean Taxonomy
A branch of science, taxonomy, allocates living creatures into different categories or classifications in order to provide a way for humans to more easily understand living things. Classifications are characterized by shared features. Carl Linneas categorized living things into a system called Linnaean Taxonomy, and a way of naming them called binomial nomenclature, which gives an organism a genus and species name. For example:
1. Rock Bass – common name, and commonly found in Georgian Bay
Linneas categorized living things into a system called Linnaean Taxonomy, and a way of naming them called binomial nomenclature, which gives an organism a genus and species name. For example:
1. Rock Bass – common name, and commonly found in Georgian Bay
Genus – Amblophites
Species – rupestris
Scientific name – Ambloplites rupestris
2. Shadow Bass – common name, found in Southern US like Louisiana
Genus – Ambloplites
Species – ariommus
Scientific name – Ambloplites ariommus

The Linnaean classification system, specified in Carl Linnaeus’s Systema Naturae (1735) divided living things through a process of narrowing categorization. This methodology evolved into the narrow classification system that is used today, and noted below.

From broadest – (1) Kingdom (2) Phylum or Division (3) Class (4) Order(5) Family(6) Genus(7) Species– to specific

Life starts as a parasite on a host fish

Eastern elliptio or  	Elliptio complanata
Elliptio complanata are medium to large sized freshwater mussels of the family Unionidae. Most Unionidae mussels in their larvae stage need to attach themselves to a host fish to in order for the larvae to survive and metamorphasize into juveniles . The larva that are released from mature Unionidae mussels are called glochidia.

Some mussels simply release glochidia into the water where by happenstance they can contact with the appropriate fish host as it swims by.
Other mussels of this family have a more intricate process such as acting as a kind of lure to attract host fish to them or sending out glochidia in tiny structures that trick host fish into thinking they are food.

One the glochidia get attached to the the gills or the fins of the right fish host , they must embed themselves enough that the host's fish tissue grows over the glochidia. Metamorphosis into microscopic juveniles takes place over days or weeks, depending on species and temperature. Finally, a new mussel bed is created if the juveniles fatefully manage to drop off into a suitable habitat.

Valves or Shells

You'll find most Elliptio species sticking up with some of their shell bodies burrowed into the substrate. The interior of the shell has a kind of mother-of-pearl silvery or purplish look. Bivalve molluscs such as the Elliptio have their bodies enclosed by 2 shells joined together by a kind of a hinge ligament. The shell of a bivalve is composed of calcium carbonate.

Molluscs and rocks

What do they eat?

Unionoids sift phytoplankton and zooplankton, as well as suspended bacteria, fungal spores, and dissolved organic matter. There is no certainly into which of these filtered items are actually processed as energy. In some cases of high populations, water clarity may be influenced but is dependent on many factors some of which include: water temperature, current velocity, and particle size and concentration.

In general, freshwater mussels are a food source for fish, mammals and birds. Empty mussel shells can be used for fish to lay eggs, a refuge for crayfish and insect larvae. They are sensitive to pollution and habitat changes. Because they are filter feeders and accumulate toxins, they serve as early indicators of environmental degradation and are not recommended for human consumption as they may be filled with concentrated toxins.

Thank you for supporting the Georgian Bay Aquatic Species Library

For more information about the DNA barcoding project for Georgian Bay. Please visit here.

We can't stop now! Please donate to Georgian Bay Forever to ensure projects like these continue. Georgian Bay Forever is a charity that funds and supports scientific research, restoration projects and education that protect and enhance the waters of Georgian Bay, as part of the Great Lakes. Our vision is that Georgian Bay waters are healthy and thriving for future generations. Learn more about how you can support out work.

Sources and acknowledgements

Thank you to the sources for information in this post.

Note - We try to bring together information to help understand this species. We do use sources to provide information and visuals. We do our best to attribute properly and try very hard to get it right. If we have made an inadvertent mistake around recognizing someone’s work or misinterpreting the work, please let us know via email at communications and I will correct.

  • https://fwspubs.org/doi/pdf/10.3996/102012-JFWM-094.
  • https://en.wikipedia.org/wiki/Elliptio.
  • https://en.wikipedia.org/wiki/Bivalvia.
  • http://molluskconservation.org/MUSSELS/Reproduction.html .
  • https://www.ontarionature.org/protect/PDFs/Mussels_W08.pdf .