benthic macroinvertebrates- animals without a backbone, visible to the unaided eye, living in or on the stream bottom one of the best indicators of stream health present throughout the year population reflects environmental changes
17 Examples: insects, snails, clams, mussels, crustaceans, worms, and leeches Large proportion in a stream are insects.
18 Insects go through metamorphosis (life changes) from egg to adult. Due to these life cycles, the size and abundance of insects present in a stream will vary with the season. Insects have a rigid exoskeleton that must be replaced in order for them to grow.
19 complete metamorphosis- 4 stages (88% of all insects) egg- female insect lays eggs larva- hatch from egg, usually worm- like shape, do not look like adult pupa- inside a cocoon, larva develops adult shape (4 days to months) adult- emerges from cocoon
20 egg larva pupa adult
22 incomplete metamorphosis - 3 stages (12% of all insects) egg- female lays eggs nymph- looks like small adult, usually without wings, molt exoskeleton 4-8 times adult- insect stops molting when adult size is reached and now have grown wings
27 Seasonal Cycle Summer -eggs hatch Fall/Winter -nymphs and larva feed and grow Late Spring/Early Winter -adults emerge 7 7
28 Stream Communities and Feeding Groups Shredders -macroinvertebrates with chewing mouth parts -feed on decaying organic matter processes into finer particles -aquatic sowbugs, a few caddisfly larvae, some cranefly larvae, scuds, and most stonefly nymphs
29 Grazers / scrapers -feed on algae -most caddisfly larvae and water pennies -changes in habitat result in an increase of grazers with a decrease of shredders
30 Collectors -feed on fine organic particles -blackfly larvae, most caddisfly larvae, mayfly nymphs, midge larvae, riffle beetles, and riffle beetle larvae -collectors are found in all stream regions, but are dominant in the lower regions of a stream system
31 Predators -feed on prey -alderfly larvae, backswimmers, most beetles and beetle larvae, damselfly nymphs, dobsonfly larvae (hellgrammites), dragonfly nymphs, fishfly larvae, some stonefly nymphs, and some cranefly larvae -predators are found in all stream regions (wherever prey is found)