what are aquatic macroinvertebrates?

Aquatic macroinvertebrates are visible organisms with no backbone that spend all or most of their life in rivers, streams, lakes, and ponds (AKA water bugs!). They are a necessary part of a healthy aquatic ecosystem serving as the primary processors of organic material while also being prey to larger organisms, such as fish and other predatory macroinvertebrates.

Above: Caddisflies in cases attached to a river rock!

habitat

Certain types of macroinvertebrates require different habitat conditions. Rivers and streams, with faster flowing waters, usually have a colder temperatures and higher levels of dissolved oxygen which are ideal for stoneflies, mayflies and caddisflies. Lakes and ponds, with slower or more stagnant waters, usually have warmer temperatures and lower levels of dissolved oxygen which are tolerated by leeches, mosquitoes and midges.

Macroinvertebrates also require adequate shelter and food sources that can be provided in a diverse environment of submerged logs and woody debris, rocks and sandy substrate, riparian vegetation, decomposing leaves and other organic material that falls into the water.

the 5 c's of a healthy river

Cold

 

Clean

Clear

Complex

Connected

Life Cycles

Most aquatic invertebrates will live the majority of their life time in the water and only emerge as terrestrial adults.  There are two types of life cycles that an invertebrate will go through as it grows:

 

Complete Metamorphosis: 4 phases

  1. Eggs

  2. Larvae

  3. Pupae

  4. Adults

Incomplete Metamorphosis: 3 phases

  1. Eggs

  2. Nymphs

  3. Adults

Complete Metamorphosis

Examples of invertebrates that go through complete metamorphosis are caddisflies, midges, and crane flies

Incomplete Metamorphosis

incomplete_morph.png

Examples of invertebrates that go through incomplete metamorphosis are

mayflies, stoneflies, and dragonflies.

Anatomy

Anterior: Refers to the head end of the body/structure.

Lateral: Refers to the side of the body/structure.

Posterior: Refers to the tail end of the body/structure.

Dorsal: Refers to the upper or top part of the body/structure.

Ventral: Refers to the lower or bottom part of the body/structure. 

anatomy.png

Head: Usually capsule-like and contains the feeding apparatus of the organism.  

Thorax: Composed three segments and the location of the legs or leg-like appendages. 

Abdomen: Composed of several segments (often 8-11).

Antennae: A pair of slender movable sensory organs located on the head. 

Mandibles: A pair of appendages near the mouth used to grab, cut and chomp.

Tarsal claws: Claws located at the end of the leg.

Cerci: Appendages located on posterior end of some insects.

BioIndicators

Bioindicators are organisms that effectively indicate the condition of the environment because of their limited tolerance to environmental variability. 

Factors governing aquatic insect distribution:

  • Oxygen availability

  • Temperature

  • Sediment and substrate type

  • Presence of pollutants such as pesticides, acidic materials and heavy metals

We can use the presence of certain macroinvertebrates (stoneflies, mayflies and caddisflies) to help determine the likely health status of a river!

Learn more about macroinvertebrate orders - key characteristics for identification and stress tolerance levels! 

Intolerant 

EphemerellidaeDorsal.jpg
PerlidaeDorsal.jpg
UenoidaeCaseLateral.jpg

Tolerant 

hirudinea_ventral.jpg
oligochaeta.jpg
gastropoda_pouch.jpg

Contact Us

water@montanawatershed.org

(406) 541-9287

PO Box 9201

Missoula, MT 59807

Office closed due to COVID-19

802 E. Front St.

  • Facebook
  • Instagram
  • Twitter
  • LinkedIn

©2020 by Watershed Education Network. Proudly created with Wix.com