What’s Monitored

Looking at microbiotic organisims - rock photo by Darienne Mc Namara


Macroinvertebrates Group 2: sensitive to pollution

Many different types of caddisfly larvae
(Order Trichoptera) live in Wisconsin's
streams and rivers. Some types build cases, which they carry along with them as protection from predators and their environment.  Others spin nets to catch their prey and live in nooks and crannies of rocks and materials along the stream bottom. They obtain their oxygen through their skin, though some have gills to help obtain oxygen.

Cranefly larvae (Order Diptera) are often found in woody or rotting material and in algae along the bottom of streams. Most usually breathe through openings at the end of their body called spiracles, but in well-oxygenated water can obtain oxygen through their skin.  Most species live in the water for a year, emerging as adults in early spring.Freshwater Mussel and Fingernail Clam






Freshwater mussels and Fingernail clams (Order Pelecypoda), are filter-feeders; This makes them susceptible to pollution. They can be negatively affected by pollutants that are suspended in the water, which are filtered out as they feed.

Dragonfly larva (Order Odonata) can live in streams for less than a year or for up to four years before emerging as adults.  They are generally found in slower-flowing water or in lakes or ponds.  They might also be found buried several centimeters into the bottom sediments.  They breathe by taking water into their bodies at their "tail" end and a process of gas exchange is carried out within a rectal chamber.  They can also use the chamber to aid in movement.  They take water into the chamber and then expel it to give them a sort of jet-propelled movement.

Crayfish can be found in various aquatic habitats. They primarily eat vegetation, but will also eat animal food if plant material is not present.  They require waters with adequate amounts of oxygen, but can withstand waters with less oxygen than others in group 2.  They are included in group 2 because they are sensitive to toxic substances that can accumulate in animals of plants that they may eat.



Damselfly larvae (Order Odonata) are found in both flowing and still waters. They move through the water by moving their abdomen and "tails" (called lamellae) back and forth from side to side. They also use the lamellae to aid in breathing. The lamellae make the surface area of their skin larger, which increases the amount of oxygen they get.

Water Penny larvae (Order Coleoptera), like Group 1 organisms, rely on moving or fairly-well oxygenated waters for survival. However, rather than being dependent upon food sources from the natural environment, such as leaves, their main food source is algae, which they scrape off rocks.  Algal growth can increase when there are more nutrient sources within a stream, and thus these organisms are included in Group 2.

Riffle beetles (Order Coleoptera) are somewhat unique among the biotic index organisms, as both juveniles and adults live in the water, while for most organisms included in the index, only the larvae live in the water.  Like their name suggests, these beetles are often found in stream's riffles (areas of fairly shallow depth and fast-flowing water), but they can also be found in vegetated areas of slower flow.  Larva breathe using gills, while adults use what is called a plastron.

Mayfly larvae
(Order Ephemeroptera)
can be found in numerous types of habitats within streams.  Some, like the flathead mayfly (above left), are found on rocks within fast-flowing riffle areas.  Others, like the burrowing mayfly (above right), are found buried within the substrates.  Still other, like the swimming mayfly (above middle) are Mayfly Larvaefound in less swiftly-moving waters, but which still have adequate dissolved concentrations.  They eat detritus or algae within the water and obtain their oxygen through gills found along the sides of their abdomens.












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