Aquatic Insect Orders

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

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

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

Oxygen Supplies Air: 200,000 ppm (20%) Lotic environments (15 ppm) –Depends on O 2 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

How do aquatic insects obtain oxygen? Atmospheric oxygen –Keep part of body out of water –Carry oxygen into water Aqueous oxygen –Specialized tracheal systems

Tracheal System

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?

Open tracheal system in flies Respiratory siphons near abdomen or thorax Different location in mosquito pupa than larva

Open tracheal system in diving beetles Bubble stored beneath elytra Gas exchange can occur in water

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

Lotic Adaptations Flattened bodies Attachment through suckers Water pennies (Coleoptera: Psephenidae) Net-winged midges (Diptera: Blephariceridae

More Lotic Adaptations Nets & Cases Trichoptera net Trichoptera cases

Lentic Adaptations Taking advantage of surface tension of still water Water Strider (Gerridae) Whirligig Beetle (Gyrinidae)

Adaptations to nearly anoxic environments Hemoglobins –Many larval chironomid midges (Diptera) = bloodworms –Very, very high affinity for oxygen (unlike us)

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

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?

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

Plecoptera Mostly temperate regions instars Closed tracheal system with anal gills. Need high oxygen, good environmental indicators.

Hemiptera: True Bugs Diving or at surface Adults and naiads both aquatic. Highly modified legs. Generally wings still functional as adults, can disperse between waterways. Notonectidae: Backswimmers Corixidae: Water Boatmen Naucoridae: Creeping water bugs Gerridae: Water striders

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

Trichoptera Case & net makers. Abdominal tracheal gills.

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

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

Megaloptera & Neuroptera