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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 • All of these have terrestrial adults. 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 • 10-33 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. Gerridae: Water striders Notonectidae: Backswimmers Corixidae: Water Boatmen Naucoridae: Creeping water bugs 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 Open tracheal system in flies • Respiratory siphons near abdomen or thorax • Different location in mosquito pupa than larva 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 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