Lecture 18: Aquatic Entomology

Immatures always in water

- Ephemeroptera: Mayflies
- Odonata: Dragonflies and Damselflies
- Plecoptera: Stoneflies
- Trichopterans

Immatures may be in water

- Diptera: Mosquitos develop in water
- Hemiptera: Some
- Coleopterans
- Neuroptera
- Megaloptera

Some of these groups are Hemimetabolous and Holometabolous

This is because the larvae and adults are in different environments. They are separated from adults, allowing for less resource competition

Challenges living in water?

- Respiration is important for living cells, organisms that live in water have to get air somehow.
- In air = 200K ppm of oxygen, in air its 15ppm
- Lotic water
- Lentic water

Lotic water

water is flowing, could be slowly flowing, but still moving

Lentic Water

Water is still, ponds or lakes

Gas exchange by diffusion

- Depends on diffusion
- Oxygen diffuses from high to low concentration
- Fast in air, slow in water
- Happens slower when it has to get through cuticles (spiracles)
- Insects deal with gas exchange in different ways

Closed Tracheal System -- Gills

Either internal or external gills. Four types of gills

Four types of gills

- Thoracic (stonefly naiads)
- Abdominal (ephemeropteran/Neuropterans)
- Caudal (Damselfly)
- Anal (Odonata)

Closed Tracheal System -- Cutaneous Respiration

- Respire through cuticle
- No spiracles or gills (rare)
- Hemoglobins in hemolymph that has high affinity for oxygen
- Hemolymph for moving nutrients not gas exchange

EX: Close Cutaneous Respiration Chironomidae

- Non-biting midges
- As immatures they are aquatic and have bright red color from the hemoglobin in their hemolymph
- Hemoglobin gets oxygen to the cells that need it
- Indicative of healthy water systems

Pest Management

Oil is used to cover spiracles of pest insect inmates that respirate like this

Open tracheal systems: Suspension in water meniscus

- Modified spiracles or tracheal systems that allows them to spend time in or on the water
- Some insects suspend themselves in water meniscus --> thriving
- Water caudal breathing tubes that break through water tension, allowing spiracles to be in air
- Scleratized siphons with a spiracle at the end of it to allow them to break through the water surface tension to get oxygen

Giant Water Bugs

Get spiracles through meniscus to get oxygen

Compressible Gills

- Predacious diving beetles
- Swim under water with a big air bubble attached to their posterior
- Bubble has oxygen they need to be able to dive for a while
- They keep the bubble there because they have a cavity at the posterior end of abdomen that compresses

Incompressible Gills

- Create plastron
- Seen in water boatmen
- Hairs over their body trap a layer of air against their spiracles while they are underwater
- Hydrophobic hairs are plastron

Aquatic Environments - Lotic

- Lots of boulders and large rocks
- As water flows there is a high volume of food
- Higher oxygen level, as it flows gathers more oxygen
- Since it moves swiftly, insects have to be good swimmers or have the ability to hang onto something so they aren't swept downstream

Lotic Water Adaptations

- Insects generally dorsoventrally flattened, immature water pennies are dorsoventrally
- Allows water to flow over t while it holds onto a rock
- Some immatures have portable larval cases
- Many of these insects have a sucker on their body to help them hold on (suction cup)
- Immatures also have hooks or webbing that perform the same purposes as a sucker (EX: blackly have hooks)

Portable Larval Cases

- Protects them from being washed downstream
- Trichopterans (Cattisfly larvae)
- Immatures use silk and substrate to build little cases that act as shelters. Made from stones and stick-wide variety of cases

Aquatic Environments - Lentic

- Insects that live in still water are usually on the surface of the water
- There is poor food volume in lentic water (insects hunt for their food)
-There's lots of insect predators in these systems, there's also poor oxygen supply
- Insects need to have diverse mechanisms of gas exchange to be able to thrive in lentic water

Lentic Water Adaptations

- Insects are semi aquatic-neustic
- They come and go to the water, easier to do if they're on the surface
- Lots of tarsi with hydrophobic hairs that allow them to be on the top of the water
- Predators: adaptation for raptorial forelegs (giant water bugs)
- Might have good vision, but have modified compound eyes that allow them to see above and below ground below the water at the same time
- Water striders, hydrophobic hairs allow them to stay on top of water

Environmental Monitoring

- Aquatic insect communities are good for monitoring the environment because they're sensitive to water quality
- Healthy water environment will have a high diversity and relative abundance of aquatic insects
- Not many insects in the ocean