Aquatic Insects

Why should we study aquatic insects

• Vectors of disease

• Food for higher trophic levels

• Indicators of water pollution

Aquatic insect diseases

• Zika

• West Nile

• Malaria

• Yellow Fever

• River Blindness

Taxa key to indicators of water pollution

• Ephemeroptera

• Plecoptera

• Trichoptera

Primary aquatic

Originated there

Secondary aquatic

Moved to freshwater later

Adult

Imago : Usually winged stage, sexually mature

Subimago

Dun : Subadult, winged form but not sexually mature

• ONLY IN EPHEMEROPTER

Larva

Larvae : Immature stage

• Usually for holometabolous

Nymphs

Usually used for

• Mayflies

• Stoneflies

• Dragonflies

Naiad

Used for immature forms of

• Dragonflies/Damselflies

• Mayflies

• Stoneflie

Example of insect that is only aquatic when larval/nymph

Ephemeroptera (Mayflies)

Example of insect that is aquatic in both larval and adult stage

Dytiscidae (Coleoptera) - Predaceous diving beetle

Example of insect that only aquatic in its adult stage

Dryopidae (Coleoptera) - Long toes beetle

• Larvae live in soil nearby

Semi Aquatic insects

• Live along the shore, moist habitats

• Live on top of water (I.e. Gerridae)

Lentic

Still water

• Ponds

• Lakes

• Vernal Pools

Lotic

Flowing water

• Stream

Problems for aquatic insects

1. Getting oxygen

2. Staying put, moving around water

3. Osmotic regulation

4. Changes in water chemistry

Aeropneustic insects

• Use Atmospheric O2

  • Advantage : Allow them to live with low O2 levels

  • Disadvantage : Limits how long they can be underwater

Hydropneustic Insects

• Used Dissolved O2

  • Advantage: Can stay under water indefinitely

  • Disadvantage: Can only live in water with higher O2 levels

Adaptation for oxygen uptake for aquatic insects

• Reduce spiracles and move posterior

• Surrounded with hydrophobic hairs

Examples of insects that carry oxygen with an air bubble

• Dytiscidae (Coleoptera)

• Blastomatatidae (Hemiptera)

Plastron

hydrophobic hairs that repel water

Hydropneustic adaptations

Gills of some form, O2 diffuses across tissu

Benefits and costs of gills

• Never have to come to the surface to breath

• Limits insects to areas with high levels of DO

Adaptations for moving in water

• Swimming legs - i.e Gyrinidae

• Grasping legs - i.e Dryopidae

Adaptation for staying still in water

• Ventral suction cup - i.e Diptera (Black fly larva) , Trichoptera (Caddisfly)

• Streamlined body shape - i.e Pisciform Mayfly

• Hide in boundary layer - i.e flat headed mayfly

Collectors example

Ephemeroptera : Isonychiidae

Grazers example

Ephemerellidae (Ephermeroptera)

Example of shredder

Plecopter, Corydalidae (Megaloptera)

Threats to aquatic insects

• Toxins in water

• Excess nutrients (lowers O2)

• Silt build up

• Dams

• Increase stream temps

• Channeling a stream

Silt build up

• Caused by erosion and construction projects

• Covers rocks, kills algae and smothers insects, creates mud habitat

Dams

• Changes rive to lake habitat

• Can change water temperature in the steam 

Channeling stream

• Increases water velocity

• Removes pools and riffles

• Remove floodplain, causes flooding