Aquatic Insect Orders

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Aquatic Insect Orders
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Aquatic Insects

• Insects are largely terrestrial.
• But there have been numerous colonizations of the
  freshwater aquatic environment.
• Far fewer colonizations of marine aquatic
  environment.

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Aquatic Insects

• Some lineages have almost exclusively aquatic
  naiads.
• Ephemeroptera
• Odonata
• Plecoptera (the only aquatic Polyneoptera)
• All of these have terrestrial adults.

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Habitats for aquatic insects

• Lotic flowing water
• Influenced strongly by velocity of flow
• Particle size
• Substrate type
• Inputs from outside and local nutrient supplies
• Lentic standing water
• Often strong zonation
• Limnetic zone- penetrated by light
• Profundal zone- deeper zone w/o much light

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Oxygen Supplies

• Air 200,000 ppm (20)
• Lotic environments (15 ppm)
• Depends on O2 production/consumption by plants
• Affected by turbulence and water quality
• Lentic environments
• Oxygen levels vary with temperature, salinity,
  and depth
• Turbulence affects nutrient and oxygen
  distribution
• Anoxic
• No oxygen present

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How do aquatic insects obtain oxygen?

• Atmospheric oxygen
• Keep part of body out of water
• Carry oxygen into water
• Aqueous oxygen
• Specialized tracheal systems

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Tracheal System
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Closed Tracheal System

• Gills- lamellar extensions of tracheal system
• Found in many insect orders
• Gills may be in many places
• Base of legs
• Abdomen
• End of abdomen
• How is this analogous to insect ears?

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Open tracheal system in flies

• Respiratory siphons near abdomen or thorax
• Different location in mosquito pupa than larva

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Open tracheal system in diving beetles

• Bubble stored beneath elytra
• Gas exchange can occur in water

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Other air bubble gills

• Water kept away from body through hairs or
  mesh
• Oxygen diffuses from water to air against body
• Usually slow moving insects with low oxygen demand

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Lotic Adaptations

• Flattened bodies
• Attachment through suckers

Water pennies (Coleoptera Psephenidae)
Net-winged midges (Diptera Blephariceridae
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More Lotic Adaptations

• Nets Cases

Trichoptera net
Trichoptera cases
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Lentic Adaptations

• Taking advantage of surface tension of still water

Water Strider (Gerridae)
Whirligig Beetle (Gyrinidae)
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Adaptations to nearly anoxic environments

• Hemoglobins
• Many larval chironomid midges (Diptera)
  bloodworms
• Very, very high affinity for oxygen (unlike us)

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Using insects to monitor aquatic environments

• Usefulness
• Diverse taxa to choose from, many common
• Functionally important to ecological community
• Ease of sampling many individuals without major
  ethical constraints
• Ability to identify species
• Responses
• Increases of certain taxa in waters with
  sediment, low
• Oxygen, increases in temperature
• Loss of diversity with pollution and or
  eutrophication

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Ephemeroptera

• Naiads often with abdominal gills
• Also maxillary and labial gills!
• Generally 3 styli on naiads and adults.
• As many as 45 instars
• Anything else?

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Odonata

• Dragonflies Damselflies
• Rectal/anal internal gills.
• Caudal lamellae also serve as gills.
• Up to 20 instars.
• Predators as naiads and adults.

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Plecoptera

• Mostly temperate regions
• 10-33 instars
• Closed tracheal system with anal gills.
• Need high oxygen, good environmental indicators.

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Hemiptera True Bugs
Notonectidae Backswimmers

• Diving or at surface
• Adults and naiads both aquatic.
• Highly modified legs.
• Generally wings still functional as adults, can
  disperse between waterways.

Corixidae Water Boatmen
Naucoridae Creeping water bugs
Gerridae Water striders
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Hemiptera

• Left Nepidae (water scorpions) tails are
  breathing tubes
• Right Belostomatidae (toe-biters) egg tending by
  males

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Trichoptera

• Case net makers.
• Abdominal tracheal gills.

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Coleoptera

• Aquatic larvae, aquatic adults
• Aquatic larvae, terrestrial adults
• Terrestrial larvae, aquatic adults
• Pretty much all pupate on land

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Diptera

• Often with anal spiracles breathing at surface
• Very diverse
• Almost all disease vectoring Diptera have aquatic
  larvae (?)

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Megaloptera Neuroptera