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Freshwater Animals

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Title: Aquatic Animals Author: mph13 Last modified by: mph13 Created Date: 2/28/2003 10:56:06 AM Document presentation format: On-screen Show Company – PowerPoint PPT presentation

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Title: Freshwater Animals


1
Freshwater Animals
Note Ctenophores and Echinodermata are marine
phyla all other phyla have representatives in
freshwater.
2
Phylum Porifera The sponges
  • Sponges are mainly marine but there are 25
    freshwater species described.
  • Primitive multicellular animals do not have
    organs, but do have specialized cells for
    feeding, digestion.
  • Filter feeders sieve particles from the water as
    it flows into pores.
  • Some species have symbiotic algae (similar to
    corals), mainly green algae Chlorella.

3
Can be important consumers of microbes as small
as bacteria
4
Cnidaria Celenterates(Hydra Jellies)
  • Most species marine all display radial symmetry
    and possess nematocysts (defense cells).
  • Hydra is probably most common freshwater
    cnidarian
  • May have symbiotic algae, Chlorella.
  • Most often sessile epiphytic

5
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6
Platyhelminthes and Nemertea
  • Turbellaria (free-living flatworms) are most
    common in freshwater benthic habitats or
    epiphytic.
  • Some planaria acquire nematocysts for defense
    by ingesting hydra (marine forms do so as well).
  • Trematoda (flukes), a major group of animal
    parasites some with aquatic phase in life cycle.
  • Schistosomiasis is a disease of the human
    intestinal tract caused by a Schistosoma fluke.
    A similar fluke causes swimmers itch in humans we
    get infected as an alternate host (normally water
    fowl).
  • Nemertea have an anus and closed circulatory
    system.

7
Schistosoma life history
8
Nematoda The roundworms
  • Non-segmented roundworms common in all kinds of
    aquatic habitats (damp soil, freshwater, marine).
  • Generally benthic infauna (within sediments).
  • Feeding strategy varied detrivores, herbivores,
    carnivores (including predation on other
    nematodes).
  • Some species are common and important parasites
    of animals (including humans), often using
    insects as host vectors. (e.g. river
    blindness, onchocerciasis transmitted by
    blackfly (Simuliidae).

(and rotifers)
9
Rotatoria (Rotifers)
  • 2000 freshwater species, more diverse than in
    marine habitats!
  • Possess an advanced digestive system including
    mastax (to grind food down), stomach, intestine,
    anus. Possess a nervous system and sensory
    organs (eyes).
  • Sexual reproduction produces a dormant cyst and
    several species can survive years of drought.
  • Wheel organ is ciliated and creates a
    whirlpool-like flow to bring prey to mouth. Some
    modified for ambush capture.
  • Predators of bacteria and small protists like
    nanoflagellates.
  • May be planktonic or attached by foot (with
    toes).

10
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11
Mollusca Soft-bodied, unsegmented possess a
head, muscular foot, stomach/viscera, and often
grow a calcareous shell.
  • Class Gastropoda snails and limpets
  • 500 species of freshwater snails
  • One-piece shell and a radula (file-like
    structure) that is used to scrape food from
    surfaces
  • Snails are important grazers of periphyton
    (epilithic algae, bacteria, etc.) but also feed
    upon detritus, macrophytes, and dead tissue

Conical shell
Spiral shell
12
  • Class Bivalvia clams and mussels
  • Bivalves have a shell with two halves and gills
    specialized for filter feeding.
  • Found in the benthos, either burrowed in
    sediments or attached to substrate.
  • Adults can withstand periods of drought by
    closing shell.
  • Some have specialized larval stages with
    interesting dispersal characteristics.
  • Some bivalve species are important invaders of
    North American aquatic systems (alien species
    Asiatic clam, zebra mussles) with serious
    ecological implications.

13
Annelida Segmented worms
  • Tubular, segmented body with specialized
    digestive system, terminal mouth and anus.
    Familiar representatives include oligocheates,
    leeches.
  • Oligocheates (like familiar earth worms)
    benthic, burrow through sediment.
  • Most ingest organic particles in sediments
    (important connection in food chain) some algal
    grazers or predators.
  • Resistant to low oxygen and polluted conditions
    (good indicator species Tubifex).
  • Vectors of some important parasites, e.g.
    Whirling Disease

14
Hirudinea (Leeches)
15
Whirling Disease of Trout
Tubifex sp.
Myxobolus cerebralis
16
Arthropoda
  • Ubiquitous in all continental surface waters.
  • Important in linkages of ecosystems. (aquatic and
    terrestrial)
  • All arthropods characterized by
  • Chitinous exoskeleton
  • Stiff jointed appendages (mouth, legs, etc.)

17
Arachnida Mites and Spiders
  • No true aquatic spiders some able to utilize the
    environment on occasion.
  • Water mites are diverse and inhabit most surface
    waters.
  • Mostly benthic, but some pelagic species in
    lakes.
  • Almost all predatory (mainly on insects) but some
    parasitic (often in larval stage).

Mouth
Fused cephalothorax and abdomen
Six pairs of appendages, 4 pairs of legs most
conspicuous
18
Subphylum Insecta
  • Ten orders contain aquatic species majority are
    aquatic as larvae, emerge as adults.
  • Characterized by
  • body divided into head, thorax (three segments),
    and abdomen
  • Single pair antennae, compound eyes, specialized
    mouthparts
  • Order Collembola (springtails) Not true insects.
  • Wingless, often eyeless.
  • Mostly terrestrial or semiaquatic, often in lakes
  • Poorly studied

19
Order Plecoptera
  • Stoneflies most common in streams some predators
    and others detritivores.
  • Sensitive to pollution and low oxygen levels,
    therefore used as an indicator species.
  • Similar in appearance to mayfly larvae except
    only have two cerci (filaments) on posterior end,
    and tend to be mostly flattened.
  • Incomplete metamorphosis

20
Incomplete Metamorphosis
21
Order Ephemeroptera Mayflies
  • Aquatic only as larvae common in streams and in
    lake benthos. Feed by scraping, collecting, some
    predatory
  • Many species, typically divided by habitat
    interaction or behavior swimmers, clingers,
    crawlers, burrowers. Body shape reflects
    lifestyle
  • Clingers flattened dorso-ventrally
  • Swimmers round streamlined
  • Burrowers often have tusk-like mandibles
  • Crawlers have more streamlined gills than
    burrowers

Gills
Three filaments
22
  • Mayfly life cycle
  • Eggs hatch in water, larvae grows.
  • Larvae swims to surface and emerges
    metamorphoses into sub-adult (subimago) form.
  • Subimago matures into adult. Adult mates, female
    lays eggs in water, dies.

23
Order Odonata dragonflies, damselflies
  • Aquatic as larvae in both streams and lakes (more
    in lakes and slow waters). Important predators
    of other insect larvae.
  • Move by crawling, some by swimming. Prefer thick
    aquatic vegetation for cover, debris/litter,
    rocky cobble, or burrow in sediments.
  • Three-stage lifecycle similar to mayflies. This
    lifecycle is termed incomplete metamorphosis.

24
Order Trichoptera
  • Caddisflies mostly lotic, a few lentic species
    aquatic as larvae and pupae
  • Variety of lifestyles habits
  • Some build protective cases from materials in the
    environment, crawl and graze on periphyton or
    leaf litter
  • Some construct nets for filter-feeding
  • Others free-living, predatory

25
Complete Metamorphosis
26
Order Megaloptera
  • Dobsonflies, alderflies aquatic as larvae, pupae
  • Often large larvae with large mandibles all
    predators.
  • Aquatic period of life cycle can last several
    years before emerging as adults.
  • Occur in both lotic and lentic systems.

27
Order Heteroptera
  • The true bugs are mostly terrestrial aquatic
    species live either on surface or submersed.
  • Inhabit both lentic and lotic environments many
    possess specialized appendages adapted for
    swimming or to facilitate air breathing.

28
Order Lepidoptera
  • Very few aquatic species of moths or butterflies
    usually associated with ponds with dense
    macrophyte populations. Some lotic species
    grazers of periphyton.
  • Complete metamorphosis.

Paired, filamentous gills
29
Order Coleoptera
  • Though only about 3 of beetles aquatic, there
    are so many species of beetles that this still
    represents a significant order of aquatic
    insects.
  • Some submerge water bubbles for air breathing.
  • Includes predators, periphyton and macrophyte
    grazers.

30
Order Diptera True Flies
  • Largest group of aquatic insects, dominated by
    family Chironomidae (midges).
  • Also includes nuisances like mosquitoes, black
    flies
  • Some midge larvae possess hemoglobin as an
    adaptation for survival in low oxygen
    environments.

31
Subphylum Crustacea
  • 4000 species of crustaceans found in freshwaters
    although most are marine.
  • Includes many important food chain links
  • Zooplankton species are key as primary consumers
    (plankton grazers)
  • Benthic omnivores which feed upon detritus,
    carrion, etc.
  • Characterized by
  • Respiration across gills or body surface
  • Chitinous exoskeleton, two pairs antennae, paired
    and jointed appendages

32
Ostracoda
  • Seed shrimp are benthic species covered by
    carapace made of mix of chitin and calcium
    carbonate.
  • Mostly graze algae or eat detritus.
  • When ostracod dies, carapace resists dissolution
    can be found in sediment cores, fossils.
  • Isotopic composition of recovered carapace can
    reveal past climate patterns (temperature).

33
Copepoda
  • Important pelagic zooplankton, but other species
    also benthic in streams, lakes and groundwater,
    or parasitic.
  • Sexual reproduction, characterized by a
    many-staged development process divided between 6
    naupliar (analogous to larval) and 6 copepodite
    (juvenile) stages.
  • Interesting patterns of diverse morphology,
    adaptations and speciation.

34
Branchiopoda
  • Diverse group including Cladocera, tadpole
    shrimp, brine shrimp, etc.
  • Usually found in lentic environments. Some
    benthic, some planktonic.
  • Many species have an egg stage that is resistant
    to drying and can withstand long periods out of
    water.

35
Decapoda
  • Includes many large (macroinvertebrate) species
    such as crayfish, shrimp, crabs.
  • Inhabit lentic and lotic environments, including
    caves, groundwaters, wetlands.
  • Some species have high value as food for humans
    these are often cultured and harvested.
  • Crayfish are omnivorous and important benthic
    consumers shrimp are primarily grazers or
    detritivores.
  • Important as both consumers and as prey for
    larger vertebrates.

36
Isopoda
  • Pillbugs, sowbugs terrestrial, marine and
    freshwater species.
  • Often found in clean, oxygenated water (springs,
    streams, groundwaters).
  • Detritivores and scavengers.

37
Amphipoda
  • Scuds and side-swimmers resemble isopods but are
    flattened laterally, not dorso-ventrally.
  • Omnivorous scavengers some important shredders
    of CPOM mainly benthic.

38
The Vertebrates
  • In freshwaters, fish are considered the most
    important vertebrate species.
  • Most diverse aquatic vertebrates, over 24,000
    species described half found in freshwater.
  • Dominant classes
  • Superclass Pertomyzontiformes, jawless fishes
    (lampreys)
  • Class Chondrichthyes, cartilaginous fishes
  • Class Osteichthyes, bony fishes

39
  • Fish can be found as predators, grazers,
    scrapers
  • Body form is adapted and specialized toward
    certain lifestyle / behavior
  • Streamlined fishes are specialized for near
    constant swimming for locating and pursuing prey
  • Elongate, torpedo-shaped fishes specialized as
    sit-and-wait ambush predators built for burst
    speed.
  • Benthic species often flattened dorso-ventrally,
    with under-slung mouths
  • Deep-bodied, ventrally flattened fish are
    specialized for maneuvering in tight quarters
  • Eels are adapted for moving through narrow spaces

40
Tetrapods
  • Other aquatic vertebrates include amphibians,
    reptiles, birds and mammals.
  • Amphibians include salamanders, frogs mostly
    predators but some are algal grazers and
    detritivores (especially as larvae).
  • Amphibians have recently gained much attention as
    indicator species of aquatic pollution and
    environmental changes.
  • Recent evidence suggests a worldwide decline in
    amphibian diversity some correlations to climate
    change, global warming processes.

41
Reptiles, Birds and Mammals
  • Many familiar representatives including
  • Turtles, Water snakes, Crocodilians
  • Pelicans, ducks, some raptors
  • Dolphins, bats, beavers, hippopotamus
  • These animals are often of interest as high-order
    predators, or for ways in which they alter their
    environment.
  • Mostly associated with shallow habitats and
    aquatic-terrestrial interface.
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