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Macroinvertebrates Powered By Docstoc
					Benthic means bottom dwelling and refers to organisms that live in,crawl on or attach themselves to the bottom(substrate).

Macro-invertebrates refers to invertebrates that can be seen with the unaided eye. Most benthic macro-invertebrates are aquatic insects or the aquatic stages of insects, larvae or nymphs. Macro invertebrates also include clams and worms. Macro-invertebrates can provide a useful indicator of water quality are sensitive to physical and chemical changes •many
•they can’t easily escape pollution like some fish

•they easily collected

Aquatic insects go through several stages from egg to adult. The number of stages depends on the type of metamorphosis followed. Some insects undergo incomplete metamorphosis in 3 stages •Begin as eggs •hatch into nymphs •Grow into adults Examples are mayflies, dragonflies, stoneflies, and true bugs.

Many of these are only aquatic during during the egg and nymphal stages

True bugs

Some insects undergo complete metamorphosis which has 4 stages •Egg •Larva

•Adult Examples are true flies, beetles, and caddisflies. Once again many are only aquatic during the egg, larval, and pupal stages.

Caddisflies (Order Trichoptera) All have hard-shelled head capsules, sometimes the first three segments hehind the head also have hard plates. The rest of the body is soft and cylindrical.

Often make cases of small stones or plant matter

Stoneflies (Order Plecoptera)
The nymphs require highly oxygenated water. All have two tail filaments (or cerci) Their antennae are moderately long. Head and three body segments are hardened antennae

Hardened body segments

Two tail filaments (cerci)

Mayflies (Order Ephemeroptera)
The nymphs are small and squat, or long and slender. They have three pairs of segmented legs and visible antennae. Most have three tail filaments and seven pairs of abdominal gills Flattened body shape Three tail filaments


Alderflies, Dobsonflies,Fishflies (Order Megaloptera)
These are usually the largest aquatic larvae. Usually found in clean rivers and streams with rocky bottoms. Head capsule and first three segments are hardened. Identified by presence of lateral filaments extending out from sides of each abdominal segment. The larvae are predators. Hardene d head capsule Lateral filaments


Midges (Order Chironomidae, Order Diptera)
The nymphs can survive in habitats with little dissolved oxygen. They are small larvae and lack jointed legs. But they do have a pair of small protolegs just below the head and another pair posteriorly. Head is hard whole rest of body is soft. They usually have a curved shape. protolegs

Craneflies (Order Tipulidae, Order Diptera)
The larvae are usually oblong, cylindrical and somewhat tapered toward the head. The head is retractable and only partially hardened. The last abdominal segment usually has finger-like lobes.

Finger like lobes

Other trueFlies (Order Diptera)
This group includes blackflies, horseflies, sandflies, no-seeums, deerflies, and sewageflies. They vary in size, but all lack jointed legs. Bodies are soft and flexible.

Dragonflies and Damselflies (Order Odnata)
These nymphs are not common in fast flowing streams, but abundant in sluggish waters. They may be elongated and often grey, green or brown. Bodies can be smooth or rough and often covered with a growth of algae.

Water Mites (Hydracarina)
Water mites are small aquatic relatives of spiders. They are nearly round or globular, and have eight legs. The most common mites are bright red and very small.

Snails (Order Gastropoda)
They have spiral shells, although a few have cone-like shells. It is important to note if the shell spirals from right to left!

Aquatic Worms and Leeches (Order Oligocheata Order Hirundinea)
These are multi-segmented worms similar to earthworms. Leechs are also multi-segmented, but have a flattened body and a sucker on both ends of the body. Neither group has a head capsule. They are tolerant of high siltation and organic pollution.

Aquatic Sowbugs (Order Asellus)
They are omnivores. They are micro-crustaceans and are abundant on rocks in slower-moving waters. They have may appendages lining each side of the body.

Shredders: feed on coarse plant material like leaves, grasses, algae and rooted aquatic plants. Stonefly nymphs, caddisflies and craneflies. Collectors: feed on decomposing organic matter that includes feces of upstream organisms and plant fragments. There are two types of collectors, Filters and Gathers. Filtering collectors strain minute particles out of water. Blackfly larvae and net-building caddisflies are examples. Gathering collectors feed mainly on dead organic material on the river bottom. Mayfly nymphs, caddisfly larvae, adult beetles and midges

Scrapers: feed on periphyton (attached algae) growing on stones and other substrate. They are exposed to currents have adapted bodies. Mayflies, caddisflies, and water penny are examples. Flattened body shape of water penny, a representative scraper

Predators: feed on other aquatic insects and have adaptations for capturing prey. Scoop-like lower jaws (dragonflies and damselflies), large pincer-like jaws (hellgrammites), and spear-like mouth parts (water strdiers). Other predators include large stonefly nymphs, true bugs and

1. Water temperature patterns 2. Discharge patterns (volume and velocity of flow) 3. Substrates (stream bottom composition) 4. Energy (trophic) relationships

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