The organismsgeneralities

1
The organisms--generalities

• Few dwell in water column (exception fish)
• Most associated with sediment
• Most widely studied-Macroinvertebrates Fish
• Autotrophic--Acquire energy from sunlight
  materials from non-organic sources
• Heterotrophicacquire energy and materials from
  organic sources

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Bacteria

• Present in large numbers
• 5.2 x 104 to 2.5 x 107 cells ml1 in water
• Over 107 cells in sediment
• Main users of dissolved organic material
• Occur in association with decomposing organic
  matter and biofilms
• Heterotrophic

3
Fungi

• Knowledge restricted
• Colonize leaves that fall into streams
  condition (makes the leaf more palatable
  nutritious begins the breakdown process)
• Heterotrophic

4
The autotrophs

• Algae
• Mosses
• Macrophytes
• All acquire energy from sunlight materials from
  non-organic sources

5
Algae

• Most significant primary producers
• Macroalgaemostly filamentous, tufts on rocks,
  often included in macrophytes when large
• Microalgaemicroscopic
• Periphytonalgae cyanobacterial colonies
• Main food source for grazer/herbivores
• On mineral substrateepilithic
• On plantsepiphytic
• Phytoplanktonoccur chiefly in lowland rivers
  backwaters

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Microalgae

• Periphytonalgae cyanobacterial colonies
• Main food source for grazer/herbivores
• On mineral substrateepilithic
• On plantsepiphytic
• Phytoplanktonoccur chiefly in lowland rivers
  backwaters

7
Mosses

• May be important when substrate is stable, where
  low light levels reduce periphyton
• Some truly aquatic other semi-aquatic
• Importance
• Greater structural complexity
• Rarely eaten, but periphyton grows on it traps
  detritusmore food

8
Macrophytes

• Flowering plants
• Submersed only where light reaches
• Importance
• Rarely eaten by invertebrates when alive
  (chemical defense)
• increase structural complexity provide surface
  for periphyton growth
• Ducks, grass carp can consume alive
• Into invertebrate food chain through decomposers

9
The protozoa

• Some autotrophic, some heterotrophic
• Occur where water velocity is restricted,
  particularly in interstitial (between sediment
  particles) habitats
• Eat bacteria, can be eaten by small invertebrates
• Importance in streams unknown

10
Turbellaria (flatworms)

• Tricladida (planarians) about 100 species
  microturbellarians about 400 species
• Triclads are flattened about 5-30 mm long glide
  on substrate
• Most cold-loving species, abundant in headwater
  streams
• Heterotrophic, detect food chemically
• Rarely eaten by other predators

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Mollusca Gastropoda

• Snails--most with hard external shell
• Prosobranchiaa hard operculum closes the
  entrance to the shell
• Pulmonatawithout an operculum
• Generally favor streams with high calcium (some
  exceptions)
• Shallow water, feed on periphyton (with scraping
  radula) some on detritus

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Mollusca Bivalvia

• Unionaceansfreshwater mussels
• Restricted distribution, many in large rivers
• Large, long lived (some 100 yrs)
• Juveniles (larvae called glochidia) parasitic on
  fish
• Sphaeriids
• Wide distributions, typically small
• Filter feeders

13
Crustaceans

• Decapods
• Shrimp crabs
• Common in tropical
• subtropical streams
• Crayfish382 species
• Most lentic, some lotic
• Some burrow into
• stream bed or banks
• Most are omnivorous

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Crustaceans

• Amphipodslaterally compressed
• Many aquatic habitats
• Omnivorousboth dead organic material
  periphyton
• Isopods
• Many aquatic habitats
• Detritivorous

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Crustaceanssmall, meiofauna

• Ostracodesabout 1 mm long bivalve carapace
  some interstitial surface
• Cladoceransall water habitats microscopic
  interstices of rocks plankton
• Copepodsall water habitats microscopic
  interstices of rocks plankton some parasitic
  with extreme morphologies

16
Annelids

• Oligochaetesworms slow flowing marginal
  habitats deposit feeding collectors
• Hirudinaealeeches most predators, few external
  parasites

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Acariwater mites

• Frequent in both benthos and meiofauna
• 5000 species, some lotic
• Complex life cycle with one stage parasitic

18
The insects

• Most conspicuous in streams
• Typically larval (juvenile stage) is aquatic
  long lived adult stage is terrestrial short
  lived
• Most important
• Metamorphosisinsect changes from larval to adult
  form through many molts

19
Hemimetabolous (incomplete metamorphosis)

• larvae to adult larvae adult look similar
• except adult has wings

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Holometabolous (complete metamorphosis)

• larvae to pupae to adult larvae adult
  dissimilar

21
Hemimetabolous

• Ephemeropteramayflies
• Plecopterastoneflies
• Odonatadragonflies damselflies
• Hemipteratrue bugs

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Ephemeroptera--mayflies

• World wide distribution gt 2000 species
• Larvae--all aquatic
• Baetids, heptageniids ephemerellids most
  frequent
• Tree tails (sometimes two) gills for
  respiration
• Mainly grazers (algae) or collector gatherers
  (fine detritus) some predators

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Ephemeroptera--mayflies

• Adults are terrestrial hold wings vertically
  (can fold them) short lived dont feed two
  adult molts (unique) mate in swarms over markers

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Plecoptera--stoneflies

• Mostly temperate climates 1800 species
• Larvae aquatic in cool, clean, low order streams
  with stony substrates
• One group largely detritivorousexample
  Pteronarcys californicus (salmonfly)
• One group predatoryeat midges, mayflies

25
Plecoptera--stoneflies

• Adults are terrestrial, but poor fliers wings
  are folded over back
• some feed as adults
• adults attract partners by drumming

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Odonata--dragonflies and damselflies

• World wide distribution 5500 species
• Larvae aquatic more often lentic than lotic
• Larvae predators with long, hinged labium (mouth
  part)
• Adults terrestrial often large colorful
• Adults can be relatively long lived

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Odonata--dragonflies

• Anisoptera
• adults stout, wings held away from body, not
  folded
• Larvae also stout with no external gills (in
  rectal chamber)

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Odonata--damselflies

• Zygoptera
• adults delicate bodied, wings held upright, not
  folded
• Larvae also slender, with caudal gills

29
Hemiptera--true bugs

• Mainly a terrestrial group
• Both larvae and adults of one species can be
  aquatic
• About 3300 species are either aquatic or semi
  aquatic
• Water striders, backswimmers, corixids, giant
  water bug
• Most predators

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Holometabolous

• Trichopteracaddisflies
• Dipteratrue flies
• Coleoptera--beetles

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Trichoptera--caddisflies

• Diverse group world- wide distribution gt 9600
  species
• Closely related to the Lepidoptera spin silk
• Larvae--Many habitats predators, grazers,
  detrivores
• Larvae in 3 forms
• Free-living forms roving
• Net spinning
• Cased

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Trichoptera--caddisflies

• Adults terrestrial, feed on nectar

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Diptera--true flies

• Diverse group with both terrestrial aquatic
  forms
• Aquatic larvae recognized by lack of jointed,
  thoracic legs but can have prolegs and creeping
  welts
• Adults terrestrial
• Larvae extremely varied morphology

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Diptera--Simuliidae

• Black flies
• 1650 species
• Larvae are anchored via a silk pad to sediment
• Larvae collect particles with labial fans
• Adults often considered pests, can carry parasites

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Diptera--Chironomidae

• Midges
• Most speciose often most abundant group 20000
  species
• Larvae easy to get to the group, but difficult to
  get to species larvae most eat fine detritus,
  some graze
• Adults non biting

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Diptera--Tipulidae

• Craneflies
• 15000 species, many have terrestrial larvae, but
  some in lotic environments
• Larvae large, with partially retracted head
  shredders feed on decomposing leaf material
• Adults terrestrial

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Coleoptera--the beetles

• Mainly a terrestrial group
• Riffle beetles (elmids) have aquatic larvae
  adults
• Water pennies have aquatic larvae terrestrial
  adults
• Dytiscids (diving beetles) although most common
  in lentic environments predators
• Gyrinid (whirligig beetles) larvae are benthic
  predators, adults live on surface

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Vertebrates--amphibians

• Salamanders, newts, toads frogs
• Most lay eggs and have larval development in
  water often with gills adults often remain near
  water breathe through damp skin
• 4000 species, but few restricted to flowing water

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Vertebrates--reptiles

• Most reptiles are terrestrial
• Those found in freshwater (snakes, turtles and
  crocodiles) are air breathing predators
• Eggs are usually terrestrial

40
Vertebrates--birds

• Few birds are exclusively aquatic, although many
  use margins
• Aquatic forms use food resources in the water
• Dipperssix species in the world can swim
  underwater and take invertebrate prey
• Duckssome can forage in fast water

41
Vertebrates--mammals

• Provide water for all sorts of mammals, so many
  species like birds found in riparian areas
• Few species live in the water
• Beaverlow order habitats, can modify stream flow
  through damming formerly abundant, but hunting
  has done damage
• Otterslive in aquatic habitats such as streams
  and rivers population reductions