Aquatic Invertebrates

Sphiga mussels are similar to zebra mussels but less dominant due to their reliance on specific habitat types. Sphiga mussels generally prefer deeper water than zebra mussels.
Zebra mussel larvae are planktonic, meaning they drift in the water column and cannot swim against the current.
Planktonic organisms are moved by currents, including wind-driven currents across the water surface.
Zooplankton can swim but are still considered planktonic because their movement is largely determined by currents.
The opposite of planktonic is 'nectonic,' referring to organisms that actively swim.
Zebra mussels use byssal threads to attach to hard substrates.
The lack of complexity compared to Unionid mussels gives them an adaptive advantage.
Zebra mussels can coat and kill native Unionid mussels by outcompeting them for food.

Zebra mussels are filter feeders and highly prolific.
A single zebra mussel can filter approximately one liter of water per day.
They were first detected in Lake St. Clair in 1988, likely introduced through ballast water exchange.
Zebra mussels filter both phytoplankton and zooplankton from the water.
Introduction of zebra mussels in Lake Erie led to a 600% increase in water clarity within a few years.
Increased water clarity indicates a decrease in the amount of algae and other material in the water system.

Primary productivity is the base of the food/energy pyramid in an ecosystem.
The amount of primary productivity directly influences the amount of life the system can support.
A 600% increase in water clarity results in a massive decrease in primary productivity.
This decrease impacts the entire food web, reducing the number of fish and other organisms the lake can support, indicating they are "playing in a lower league".

Gastropods, such as snails, can be both terrestrial and aquatic.
Gastropods feed on epiphytic and epilithic algae.
Epiphytic algae grow on plants, while epilithic algae grow on rocks.
They may also feed on nematodes within the algae.
The nearshore areas are productive as they are the first to warm up during the day.
Macrophytes are large plants that can be floating, submergent, or emergent.
Aquatic snails move using a large muscular foot and cilia, which creates a sliding motion.
Snails scrape substrate and consume vegetative material, including decomposing organic matter.
Some snails use muscular contractions (peristalsis) to move as well.
Snails use a radula, a scraper, to remove material from plants and rocks.
Most snails are hermaphroditic and can fertilize their own eggs, leading to limited genetic exchange (essentially cloning).
Fertilized eggs are laid after approximately fourteen days through a genital pore similar to a cloaca.
Eggs can hatch within the shell in a brood pouch, appearing as live birth.
Snail eggs are sometimes laid in helical clusters, resembling frog eggs.

Snails act as intermediate hosts for various parasites, serving as vectors to terminal hosts.
Parasitic worms can be transferred from snails to fish, then to birds (e.g., great blue heron, belted kingfisher).
Disturbing this balance by removing snails could have unpredictable consequences due to complex interlinkages.
Snails are being studied as indicators of heavy metal sequestration due to their feeding habits and substrate dwelling.
Nematomorphs (horsehair worms) are parasitic roundworms that use gastropods as intermediate hosts and arthropods as terminal hosts.
Parasitic infections can have significant impacts on hosts, depending on the severity and location of the infection, e.g., a three-meter kidney worm in a mustelid.

When identifying worms, determine if they are segmented.
Unsegmented worms are either flat (planaria) or round (nematodes).
Segmented worms have regular indentations along their body, indicating internal complexity.

Leeches are segmented worms with a suction cup at both ends.
The presence of suction cups is a key identification characteristic.
Some leeches have jaws within the anterior sucker for chewing through skin (ectoparasitic, hematophagous).
Hematophagous means they eat blood.
Leeches with a large opening in the anterior sucker are free-living detritivores.
Many leeches in Ontario are non-parasitic and free-living, feeding on small invertebrates or detritus.
Free-living leeches package decomposing organic matter, making it accessible to other organisms in the food web.
Ectoparasitic leeches secrete hirudin, an enzyme that dissolves blood clots and dulls pain.
A leech can live on a single blood meal for up to 200 days.
Do not pull a leech off; instead, use heat or salt to make it detach and avoid the reintroduction of gut bacteria.
Leeches are generally hermaphroditic but typically exchange materials during coupling.
They have a clitellum, which secretes a cocoon for the exchange of reproductive materials.
Leeches are used as live bait for angling in Ontario, a unique practice in Canada.
Leeches can indicate organic contaminants like PCBs in the water.
PCBs bioaccumulate and biomagnify up the food web.
Leeches were historically used in medicine to remove excess blood based on the theory of humors.
They are still used in modern medicine to draw blood into reattached tissues to promote healing.

The more correct common term is bristle worms, referencing to the bundles of hairs.
Oligochaetes are commonly known as earthworms.
Bristle worms have bundles of hairs (chaetae) on each body segment.
Each body segment has four bundles of hair: two dorsal and two ventral.
Each body segments is a "meat doughnut with hair".
Oligochaetes can be both terrestrial and aquatic.
Fully aquatic varieties resemble terrestrial forms and exchange gases similarly.
Tubicid worms in aquatic environments extend from the substrate to increase gas exchange when dissolved oxygen levels drop.
Oligochaetes are scavengers, feeding on detritus in the substrate.
They are primary consumers, upcycling organic material back into the food web.
Oligochaetes are hermaphroditic, possessing both male and female reproductive organs.
The clitellum secretes a sticky fluid for gamete exchange during copulation.
Gametes are secreted into that fluid, creating a safe passageway for chemical combination.
Finding many oligochaetes in a kick and sweep sample indicates low dissolved oxygen and disturbance.
A large presence of oligochaetes often indicates the presence of disturbances like sand and silt from upstream development or parking lot drainage.
Leeches move to the surface in low oxygen conditions due to atmospheric pressure changes, which was formerly used in weather forecasting.
Saturated terrestrial zones cause terretrial lugworms to surface and suffer asphyxiation and predation.