Basics of Aquatic Macroinvertebrate Identification

Wetland Ecology and Management

Definition (PA Code, Chapter 93): ◦ Spend a “living portion of their life cycle” in an

aquatic environment◦ Can be seen without the aid of a microscope◦ Animals without a backbone

Examples: crayfish, snails, insect larvae

What are aquatic macroinvertebrates?

http://www.dec.ny.gov/animals/35772.html

Like plants, macroinvertebrates can serve as indicators of water quality.

Sensitive to a variety of chemical and physical stressors:◦ Nutrient loading◦ Unstable hydrology◦ Habitat destruction

Why study macroinvertebrates in wetlands?

Minnesota Pollution Control Agency staff evaluating invertebrate samples

http://www.pca.state.mn.us/

Macroinvertebrate community data can be used to:◦ Monitor the condition of a

wetland◦ Determine the

effectiveness of wetland mitigation

◦ Make decisions regarding permit issuance

How is macroinvertebrate data used by wetland managers?

Aquatic macroinvertebrates fall mainly into 3 different phyla:

◦ Phylum Mollusca

◦ Phylum Annelida

◦ Phylum Arthropoda

Aquatic Macroinvertebrate Phyla

Scientific Classification:

KingdomPhylumClassOrder

Family Genus Species

Clams and snails

Phylum Mollusca

Helisoma sp.

http://spinner.cofc.edu

Physa sp.

Stagnicola elodes

LR

Aquatic earthworms and leeches◦ Aquatic earthworms are very similar to terrestrial

earthworms – eat mud and small bits of organic bottom as they move through substrate.

Phylum Annelida

Class Malacostraca: Crayfish and Amphipods

Characteristics:◦ Large diversity in this class◦ 20-segmented body◦ Two pairs of antennae◦ Two pairs of maxillae

Phylum Arthropoda

http://www.dec.ny.gov/animals/35772.html; http://iz.carnegiemnh.org/crayfish/

Class: Insecta 3 distinct body regions

◦ Head◦ Thorax◦ Abdomen

2 pairs of wings 3 pairs of jointed legs

Phylum Arthropoda

http://www.snh.org.uk/

1 pair of antennae Compound eyes Mouthparts consisting of:

◦ 1 pair of mandibles◦ 1 pair of maxillae◦ 1 labrum◦ 1 labium

How can we identify insects?

http://bugs.bio.usyd.edu.au/

The insect body plan

Merritt and Cummins 1996

10 most common aquatic insect orders

Aquatic Insect OrdersOrder ExampleCollembola SpringtailsEphemeroptera MayfliesOdonata Dragonflies and DamselfliesPlecoptera StonefliesHemiptera True bugsMegaloptera AlderfliesTrichoptera CaddisfliesLepidoptera Butterflies and MothsColeoptera BeetlesDiptera Mosquitoes, Blackflies, Chironomids

Common name: Mayflies Nymph characteristics:

◦ Possess 2-3 tails at end of abdomen◦ Gills arise from side of abdomen

Order Ephemeroptera

http://www.dec.ny.gov/animals/7470.html

Adult characteristics:◦ VERY short-lived

Do not feed – just reproduce, then die

◦ Occur in large swarms

Swarms are so large that they can be detected on radar!

Order Ephemeroptera

Common name: Stoneflies Larval characteristics:

◦ Each leg ends in 2 claws◦ Possess 2 cerci at the end of abdomen◦ Antennae typically 4-6 times the width of the

head

Order Plecoptera

http://www.dec.ny.gov/animals/7450.html

Common name: Caddisflies Larval characteristics:

◦ Often possess 2 prolegs with hooks at tip of abdomen

◦ Can free-living or build complex casings◦ Often have thread-like gills on abdomen

Order Trichoptera

http://www.dec.ny.gov/animals/35772.html

Order TrichopteraTube Case makers

Common name: Dragonflies, Damselflies Larval characteristics:

◦ Damselflies: Delicate looking 3 caudal leaf or paddle-shaped gills at tip of

abdomen◦ Dragon flies:

Stout body, gills located inside abdomen tip

Order Odonata

http://www.dec.ny.gov/animals/35772.html

Larvae have a HUGE, hinged lower jaw that can be extended to capture prey as large as fish!

Order Odonata

Adult characteristics:◦ Dragonflies:

Wings are held out to the side when at rest Rear wings have a broader base than front pair

◦ Damselflies: Wings are held above the body when at rest Wing pairs of similar shape and size

Order Odonata

http://www.ucmp.berkeley.edu/arthropoda/uniramia/odonatoida.html

Common name: True bugs Characteristics:

◦ Mouthparts are modified into a beak called a rostrum◦ May be found with air bubble in the water◦ 1st pair of wings are modified into leathery coverings

for hindwings (hemelytra)

Order Hemiptera

http://www.dec.ny.gov/animals/35772.html

Interesting facts:

Watch out in the water! Also known as toe-biters, these bugs will take a stab at unsuspecting humans swimming in ponds or lakes.

Rostrum operates by piercing the prey, ejecting digestive enzymes into the prey, and then sucking out the digested remains.◦ Allows the bugs to feed on large prey, including snakes

and small turtles.

Order Hemiptera

Common names: Mosquitoes, Blackflies, Craneflies, Chironomids

Larval characteristics:◦ HUGE diversity, difficult to id any farther than

family◦ Lack jointed legs on the thorax◦ Often have tubercules – small, fleshy appendages

Order Diptera

http://www.dec.ny.gov/animals/35772.html

Many different “metrics” are used to describe macroinvertebrate communities.

Most common metric:◦ Taxa richness: # of taxa in a community◦ Prediction: As water quality ↓, taxa richness ↓

Related metric: ◦ EPT richness: # of Ephemeroptera, Plecoptera,

and Trichoptera taxa in a community◦ Thought to be more pollution sensitive

How to classify macroinvertebrates

Functional feeding groups◦ Measures functioning rather than structure of the

community

◦ Types of groups: Scrapers - remove attached algae Shredders – utilize large pieces of organic matter Collectors – utilize small particles of organic matter,

either by filtering or gathering them. Predators – capture prey

Other metrics

MetricPredicted response to

increasing perturbation% scrapers Decrease% collectors Variable% predators Variable% shredders Decrease% omnivores/scavengers Increase

Functional feeding groups

http://www.epa.gov

Habitat and Behavior measures Tolerance/Intolerance measures

Additional metrics

“Crawdad Dance”

Sweeping

Sampling methods