freshwater ecology

what is limnology?
The study of fresh or saline waters contained with continental boundaries including: lakes, inland seas, ponds, reservoirs, estuaries, wetlands, swamps, bogs, springs, vernal pools, tree holes, streams.
What is a limnologist? – a. J. R. Vallentyne
Freshwater Institute, Winnipeg (1969) wrote in the journal Limnology & Oceanography “ A limnologist is a zoologist who, during summertime, studies chemical and botanical aspects of geologoical problems in readily accessible lakes, 15 m deep, located in the vicinity of universities”.
editor of L&O, E. S. Deevey and professor at Yale wrote
“The head of the world’s leading eutrophication project shows understandable nostalgia for those 15 m days. University lakes of his student days have now shoaled to less than 14-m depth. A modern limnologist is best defined as a biogeochemist and self-taught systems analyst, whose favorite systems are imbedded in an exponentially increasing matrix of septic tanks.”
F. A. Forel—“Father of Limnology”
a) worked on lake Geneva, Switzerland (1868) — coined the term limnology
b) wrote 3 volumes on physics, chemistry & biology of Lake Geneva
c) wrote first textbook on limnology in 1901
Louis Agassiz 1850
a) published “Lake Superior: Its physical character, vegetation & animals also founded the Museum of comparative zoology at harvard
S. A. Forbes 1887
published “The Lake As a Microcosm”
E. A. Birge early-mid 1900’s
“Father of American Limnology”–University of Wisconsin
Paul Welch
wrote first American text on limnology in 1935 “Limnology”- -University of Michigan
Franz Ruttner
wrote “Fundamentals of Limnology” in 1940 translated to English 1964
G. E. Hutchinson–Yale University-
wrote 4 volume “Treatise on Limnology” 1957-1973
R. G. Wetzel
published first edition of “Limnology” 1975–U of Mich, U of Ala, UNC
H. B. N. Hynes–University of Waterloo
published “The ecology of running waters” 1970. “Father of Stream Ecology”
J. D. Allan
University of Mich–published “Stream Ecology” 1995
Water Global distribution
1. ocean
2. polar ice caps / glaciers
3. ground water
4. FW lakes.
Molecular structure of water
a liquid crystal, not a true fluid.
– polar hydron bonds.
matrix forms and remains a liquid
properties of water ..Density, temperature relations
stratification issues think about arctic diving – due to density , this is important ecology for ice to be on top and not in the water columon. allows animals to escape danger under the ice. The greatest density is 4C m/unit vol.
properties of water – salinity relations
density issue – think about arctic diving. salt decreases freezing point
The saltier the water, the more buoyant an object becomes.Very salty water is denser and will sink more; thus very salty water is found at the bottom. Less salty water is less dense and will float on top of the more dense salty water.
properties of water …pressure
water is 350 times denser than air
Density increases with depth
properties of water – turbidity
dissolved particulates, more turbid, more dense.
properties of water – viscosity
thickness, residence to flow
properties of water – surface tension
water strider ecology, hydron bonds orientation.
properties of water – temperature – specific heat
amount of energy required to raise one degree and cal.
properties of water – temperature – latent heat of fusion
ability to melt ice
properties of water – temperature – latent heat of vaporization
takes a lot of heat to vapor.
water to stream = 540 cal/g thats a lot to melt / raise
aquatic life forms – Neuston
organisms that live on the surface
aquatic life forms – nekton
swimming creatures. e.g. fish
aquatic life forms – plankton
floater / can move around . maybe a meter in H2O coulum.
aquatic life forms – plankton – phytoplankton
net or macroplankton >200um
nannoplankton 20-200um
ultra plankton 10-20um
picoplankton 0.2-1um
aquatic life forms – plankton – zooplankton
micro crustrations / e.g. rotifers
aquatic life forms – plankton – seston
anything floating in the water
partical material in suspetion
aquatic life forms – plankton – trypiton
dead part
aquatic life forms -benthos
animals / plants that live on the bottom
aquatic life forms – Aufwuchs
periphyton- algae that grows on surface of plants
epilithon – organims growing on rocks
biofilms- on growers
Bacteria – general
omnipresent in the biosphere- can find anywhere
prokaryotes – no organized nucleus
has cell wall of peptido-glycans
most <5 micrometers
pop. increase rapidly by asexual reproductions.
bacteria- imporatance in ecosystem energetics and process -autotrophs
can convert inorganic to organic material
bacteria- imporatance in ecosystem energetics and process
– photoautotrophs
use light Co2+H20 – carbohydrate using sun.
bacteria- imporatance in ecosystem energetics and process
use chem, use inorganic chem reaction, use for carbohydrate sythesis e.g. rust in stream bed. ocean = communities depend on chemoautotrophs
bacteria- imporatance in ecosystem energetics and process
get energy from somewhere else – soaking up enery from environment.
bacteria- imporatance in ecosystem energetics and process
-nutrient cycling
ammonia to nitriate
bacteria- imporatance in ecosystem energetics and process
– decomposition (mineralization)
organic to inorganic
bacteria- imporatance in ecosystem energetics and process
– waterborne disease organisms
these go through the population easy
cyanobacteria – bluegreen bacteria -NOT ALGAE ) – general characterisitcs
found in hot springs where there is lots of phosophous.
prokaryotes – no organized n
cell walls like bacteria _ e.g. – peptido-glycans
polysaccharide stored as glycogen
unicellular, filamentous, colonial
very tolerant of harsh environmental conditions
populations increase rapidly by asexual reproduction.
bacteria- imporatance in ecosystem energetics and process
-blooms and nitrogen
bacteria- imporatance in ecosystem energetics and process
-consequences of blooms
human concerns
– anabaena flos-aquae
microcystis sp.
both – toxic to humans
aphanozomemnon flos-aquae
toxic to fish/humans
chlorophyta -green alage general characteristics
eukaryotes – can see nucleus- membrane bound cell walls
cell walls of cellulose
polysaccharides stored as starch –
unicellular, filamentous, or colonial
populations may increase rapidly by sexual reproduction
well developed sexual reproduction-variety
important primary producers in most aquatic systems (photosynthetic)
cannot compete with cyanobacteria in low N conditions
good food for consumers
Dinophyta -dinoflagellates
produce red tide, produce oil to float.
very huigh quality food for grazers due to oils
may be limited by P and N like other algae but also Si02 (glass)
unicellular flagellates with cellulose shell (theca)
many produce red tides = toxic blooms in marine systems
pfisteria blooms in estuaries due to N pollution threat to human health
mostly unicellular but some are colonial
protoplasm encased in SI02 (glass) shell frustule or theca
Diatoms – epitheca
upper half
Diatoms – hypotheca
lower half
Diatoms – girdle
protein band holding two halves together
eukaryotes – like higher plants , but cell walls made of CHITIN – has N in it
cell walls mostly chitin
funig –
absorb Disvoled organic compounds from environment or parasities
fungi – obligate symbionts
as in lichens or mycrorhizzaw – symbolisis
fungi body forms – mycelium
for feeding and growth
fungi body forms – fruiting body
for reproduction
fungi – aquatic hyphomycetes
member of fungi imperfecti – no sexual reproduction
first organisms to begin decay processes
spread about via asexual spores.
higher plants “large plants”
growing in lakes / streams
whereever there is H20 they grow
“can choke off surface water ” Water willow” – helps form islands / land grows like strawberries – traps sediments.
strong root system – common in southern rivers.
many produce toxic chemicals, not much feeds on macrophytes
are important sources of food for things that like dead organic matter.
they take up a lot of nutrients
can regulate nutrients
good for stopping sedimentation.
A. Rotifers
General Features
a. 0.1-1.0 mm long
b. body cylindrical, sac-like or worm-like
c. body generally covered by a shell (lorica)
d. most have crown of cilia (corona) used to
swim and/or gather food
e. mastax–chitinous “jaws”
a) variously specialized for feeding
b) important feature used to identify
Rotifers – ecology
a. locomotion–most swim at some stage in
the life cycle using corona
b. feeding–many filter feed on seston but
some are predators
c. habits–may be planktonic or benthic,
single or colonial
d. anhydrobiosis–undergo dehydration and
form resistant cyst
e. periodicity–large, seasonal fluctuations in
population density
f. vertical migration–daily vertical
movement thru the water column
g. trophic relations–primary consumers and
predators–important in food webs of most
Rotifers – life history
a. mictic cycle
b. amictic cycle
cladocera “water fleas” -general features
a. 0.3-2mm long
b. definite head; body (thorax & abdomen)
enclosed in bivalved carapace(shell) of
chitin ending in a sharp spine
c. pair of conspicuous compound eyes
d. two pair of antennae: 1st small; 2nd
e. many leg like appendages used in
locomotion & feeding
Cadocera (crustaceans ) “water fleas” – ecology
a. locomotion–”jump” thru water using
antennae like oars
b. feeding–planktonic forms filter feed on
seston and select particles based on size.
benthic forms may feed on detritus or be
c. habits–most species are freshwater,
d. periodicity–large seasonal fluctuations in
e. vertical migration–daily vertical
movement in water column
f. cyclomorphosis–changes in shape in
succeeding generations
g. trophic relations–primary consumers
extremely important in food webs in many
lakes, especially for larval fishes
cladocera “water fleas” -life cycle
a. most individuals are parthenogenic
females thru most of the year producing
many young carried in brood chamber
until development is over
b. sexual females occur late in growing
season, brood 1 or 2 young, that may
become encased in a “resting chamber” or
“ephippium” for over wintering.
c. In some species, females over winter
Copepoda (crustaceans) copepods – gen. features
a. 0.5 -2.0 mm long–some up to 5 mm
b. body generally tear-drop shaped to
c. body segmented with many pairs of
appendages–no carapace
d. 1st antennae conspicuous, 2nd antennae
less so
e. single median (nauplier) eye–no
compound eyes
cladocera “water fleas” -ecology
a. locomotion–also “jump” thru water using
antennae like oars
b. feeding–planktonic forms filter feed;
benthic forms feed on detritus or are
predaceous; some are parasites
c. habits–most species are marine, about 10-
15% are freshwater. There are many
planktonic and benthic species and can be
found in virtually all aquatic habitats and
in moist soils.
d. Important in lake & stream food webs
e. periodicity–large seasonal fluctuations
f. vertical migration—daily
g. trophic relations–primary consumers– fed
on by variety of invertebrate & vertebrates
in lakes & streams
cladocera “water fleas” -life cycle
a. most species are sexual
b. release immature larvae that go through
numerous stages before becoming adults–
a marine-type life cycle
c. many diapause (form a resting stage) to
over winter or to avoid drying
Gastropods -snails- General features
a. most inhabit coiled shells made mostly
from calcium carbonate and protein–some
(limpets) have cap-like shells
b. size range from a few mm to several
c. characterized by presence of radula (for
feeding) and foot (for locomotion)
d. Prosobranchs have gills; Pulmonates have
Gastropods -snails- ecology
a. feeding–most are scrapers–scrape
surfaces for food using radula
b. habits–most are benthic or epiphytic;
distributed widely in aquatic systems
where there is sufficient calcium–
generally absent in water with acid pH.
c. trophic relations primary consumers–
provide food source for a wide variety of
aquatic predators and are very important
in food webs of most aquatic systems
Gastropods -snails- life cycle
a. Most are sexual–some hermaphroditic but
cross fertilize.
b. Females produce lots of eggs
c. Most remain active over winter
bivalves- mussels and clams -general features
a. all freshwater forms inhabit a bivalved
shell composed of calcium carbonate &
b. size range several mm up to 12 inches or
c. characterized by presence of large foot
used in locomotion
d. also characterized by presence of large gill
used for:
a) filter feeding
b) gas exchange
c) brooding eggs and/or juveniles
d) gill chamber irrigated by water
currents entering thru incurrent
bivalves- mussels and clams – ecology
a. feeding–all freshwater forms are filterfeeders
b. locomotion–most move about very little
but can “crawl” on the surface or burrow
into the substrate using the muscular foot.
Juveniles may move with water currents
c. habits–adults are benthic and generally
remain buried to one degree or another in
the substrate of lakes and some streams
d. native species very susceptible to siltation
and toxics
e. trophic relations– primary consumers–fed
on by a variety of vertebrate predators in
streams & lakes
bivalves- mussels and clams -life cycle – -spaeriidae- fingernail clams
Sphaeriidae–fingernail clams
a) most widely distributed of freshwater
b) females brood embryos to juvenile
stage and release
bivalves- mussels and clams -life cycle – -Corbicula -asian clam
a) exotic introduced at turn of century
from Asia
b) brood embryos to juvenile–very high
birth rates
c) serious biofouler
bivalves- mussels and clams -life cycle – -Dreissen – zebra musssel
a) Facultative marine exotic introduced
USA 1985—marine-type life cycle
b) females release mobile veliger larvae
c) highly invasive, stick to surfaces and
each other using byssal threads
d) super-serious bio-fouler
bivalves- mussels and clams -life cycle – -unionidae
a) many NA species rare and endangered
or threatened with extinction
b) brood embryos to glochidia which are
expelled and parasitic on particular
species of fish.
c) Failing to find the proper host fish,
glochidia die within a short time.
d) glochidia on right hosts develop into
juveniles, drop off fish and take up
residence in sediments
oligochaetes- aquatic “earthworms” general features
a. segmented worms bearing setae (chitinous
b. size range from a few mm to several
inches in length
c. most exchange gases across body wall thus
body wall is well supplied with capillaries
d. blood contains hemoglobin to transport
oxygen between exchange surface(skin)
and tissues
oligochaetes- aquatic “earthworms” – ecology
a. feeding–most feed on organic material in
the substrate
b. locomotion– move by crawling on surface
or burrowing
c. habits–most are benthic and burrow in
the substrate of lakes & streams
d. many are tolerant of low oxygen
conditions and toxic chemicals and have
been used as “indicators” of organic
e. trophic relations–primary consumers–
may be very important in some food webs
Branchiobdellida – branchiobdellids – general features
a. unevenly segmented worms that live as
commensals on crayfish
b. size range 0.8 to 10 mm length
c. mouth fitted with chitinous jaws suited for
scraping surfaces
d. posterior end fitted with sucker for
hanging on to surfaces
Branchiobdellida – branchiobdellids – ECOLOGY
a. habits–live in various creases and crevices
on crayfish and other crustaceans
b. feeding–apparently feed on biofilms
growing on crayfish
c. trophic relations–not particularly
important in most systems
1. General features
a. segmented worms (related to oligochaetes)
that are dorso-ventrally flattened
b. mouth with chitinous jaws for predation
and sucking blood
c. posterior sucker for holding on to prey
d. size 5mm to 18 inches
a. feeding-many are predators on a variety
of aquatic animals, many suck blood from
vertebrates, some are scavengers
b. trophic relations–may be significant
predators in some systems– also eaten by
Amphipoda—amphipods, scuds, or sideswimmers
1. General features
a. laterally flattened crustaceans
b. large crushing “jaws” called mandibles
used for chewing
c. body divided into 3 regions (head, thorax
& abdomen) and with chitinous
exoskeleton that contains high
concentration of Ca
d. all body regions segmented with paired
appendages on each segment-most about 1
Amphipoda—amphipods, scuds, or sideswimmers
a. feeding– most are detritivores but some
may feed on living vegetation–young feed
on biofilms
b. habits–benthic–widely distributed on and
in substrate and aquatic plants in
freshwater systems including caves &
springs—cave species frequently endemic
an are thus rare & endangered. Many
marine species
c. locomotion–”side-swimming” using
d. trophic relations–as primary consumers,
very important in food webs, especially in
springs & caves
Amphipoda—amphipods, scuds, or sideswimmers
life History
life History
a. sexual reproduction only–most breed
continuously so you always find a range of
ages(sizes) in specific populations
b. like other arthropods, the exoskeleton is
shed (molted) periodically and replaced–
this is the only time the animals can grow
larger–most species go thru about 10
“molts” between birth and adulthood
Isopoda—isopods or sow-bugs
1. General features
a. dorso-ventrally flattened crustaceans
b. also with mandibles
c. body in 3 regions, segmentation,
appendages, & exoskeleton as in
amphipods—most are <1 cm long
Isopoda—isopods or sow-bugs
a. feeding-most are detritivores and/or
scavengers–young feed on biofilms
b. habits–same as amphipods. in fact,
amphipods & isopods are almost always
found together in springs & caves. Many
are endemic to specific springs or caves
c. locomotion–mostly crawl on and in
substrate & vegetation
d. trophic relations–same as amphipods
3. Life history
a. very similar to amphipods
1. General features
a. relative large crustaceans ranging from 5
up to 35 cm
b. body divided into 2 distinct regions:
cephalothorax (fused head & thorax) and
c. 2 pairs of long antennae and 1 pair of
conspicuous compound eyes on head
d. thorax with 5 pr walking legs, first pair
enlarged chelipeds pincers) and covered
by dorsal shield (carapace)
e. abdomen with paired appendages on each
f. exoskeleton of chitin with high
concentrations of Ca
2. Ecology
2. Ecology
a. habitats–wide spread in freshwater
including caves and groundwater where
Ca is sufficient.
b. Many live under large rocks, wood, etc.–
others burrow in mud
c. feeding– some graze algae, some shred
leaves, some filter feed, most are
predators at times–call them omnivores
d. locomotion–mostly crawl but can “jet”
backward using the tail
e. trophic structure–omnivores that are
favorite food of many aquatic &
terrestrial vertebrates
Life History
a. generally breed once a year–female
broods eggs under abdomen and carries
young around for a time after hatching.
b. can only grow after molting .
A. General features of insects
1. body is divided into 3 distinct regions
a. head
a) 1 pair of antennae
b) 1 pair large compound eyes
c) 1 to several ocelli (simple eyes)
d) complex mouth parts
1) labrum-fused “upper lip”
2) mandibles-paired
3) maxillae-paired
4) labium-“lower lip”
b. thorax
a) three pairs of walking legs in larvae and adults
b) two pairs of wings in adults except for Diptera (1 pair) and some wingless forms. Wings absent in immatures
c. abdomen
a) lack true appendages but may have external structures associated with reproductive system
insects- life cycles
B. Life Cycle Types
1. General features
a. most species have relatively long lived aquatic immatures.
b. Most species have relatively short lived terrestrial adults with notable exceptions.
2. Holometabolous (complete) metamorphosis
a. life cycle has 4 stages
a) egg
b) larva—up to 6 larval stages separated by molts
c) pupa
d) adult (imago)
b. in some, all stages are aquatic
c. in most, egg, larvae, and pupae are aquatic-adults are terrestrial
d. in some, egg & larvae are aquatic, pupae and adults are terrestrial
e. in some others, eggs, larvae & adults are aquatic, pupae are terrestrial.
3. Hemimetabolous (incomplete or gradual) metamorphosis
a. life cycle has 3 stages
a) egg
b) larvae or nymph—may have up to 30 larval stages separated by molts
c) adult
b. eggs and larvae are aquatic, adults are terrestrial
C. Ephemeroptera—mayflies
1. General features
a. nymphal body flattened or cylindrical
b. generally with 3 cerci(tails) but some have 2
c. plate-like abdominal gills
d. large compound eyes and noticeable antennae
e. most have ocelli as nymphs
a. most are primary consumers–eat detritus or algae; a few are predaceous
b. wide spread in lakes, streams, and other freshwater habitats
c. nymphs are generally considered to be sensitive to pollution
d. serve as food for a variety of invertebrates & vertebrates
– life-history
a. hemimetabolous
b. nymphal life normally 5-8 mo with 12-30 instars; adults very short-lived(hours to days)
c. last nymphal instar molts into sub-imago (winged but sexually immature)—wings are smoky rather than clear as in mature adults
d. Subs go thru an additional molt to become sexually mature adults only insect that molts after becoming winged.
e. mating occurs in swarms, female dies shortly after laying eggs
D. Odonata–dragonflies & damselflies
1. General features
a. nymphal body of dragonflies broad & flat or thick and cylindrical
b. damselfly nymphs generally cylindrical and thinner
c. both with extendible, raptorial labia (lower lip) for prey capture
d. dragonfly nymphs have internal rectal gills; damselfly nymphs have external terminal gills
e. damselfly adult fold wings over back at rest; dragonfly adult wings remain spread laterally
f. large eyes, small antennae
Odonata–dragonflies & damselflies – ecology
a. wide spread in lakes, stream, marshes
b. nymphs & adults predators
c. adults display complex behaviors
d. nymphs & adults fed on by wide variety of predators
Odonata–dragonflies & damselflies -life history
3. Life History
a. hemimetabolous
b. nymphs live 1-3 years; adults live up to 3 months
c. last instar nymph crawls out of water to molt to adult
E. Plecoptera—stoneflies
1. General features
a. nymphal body cylindrical or dorso-ventrally flattened
b. nymphs always with 2 tails, no abdominal gills–may have coxal, cervical, or anal gills
c. large eyes, conspicuous ocelli, prominent antennae
Plecoptera—stoneflies- Ecology
2. Ecology
a. generally restricted to clean, cool, fast moving streams, sensitive to pollution
b. nymphs predators or detritivores; most adults don’t feed
c. adults poor flyers, secretive
d. nymphs & adults important in food webs
Plecoptera—stoneflies – life history
3. Life History
a. hemimetabolous
b. nymphal life 8 months to 4 years, adults short lived
c. last nymphal instar crawls out of water to molt into adult
emerge at all times of year including winter, adults display courtship behaviors including “drumming” on substrate to attract females
F. Hemiptera—bugs
1. General features
a. nymphs & adults have “piercing-sucking” mouth parts(stylet)– penetrate prey, release digestive enzymes, suck out dissolved insides
b. some highly adapted for swimming in water or “skating” on surface
c. many have long breathing tubes
Hemiptera—bugs- Ecology
a. nymphs and adults are predators
b. many species have fused wings, never leave the water. Some do fly and are attracted to lights
c. more species in lakes but there are some “stream” species, some occupy hot springs or saline ponds
d. many have scent glands with which they ward off predators
Hemiptera—bugs – life history
a. hemimetabolous
b. most have annual cycles
G. Megaloptera—Dobsonflies, alderflies – General features
a. larvae (called hellgrammites) with large, sclerotized head with prominent mandibles.
b. abdomen soft, very long, each segment with paired lateral filaments (with some exceptions), and pair of terminal hooks.
c. some with prominent abdominal gills at base of lateral filaments; others with dorsal breathing tubes near tip of abdomen
Megaloptera—Dobsonflies, alderflies – Ecology
2. Ecology
a. widely distributed in streams, lakes, springs, seeps
b. voracious predators
c. favorite food of many fish, each other, and other invertebrates and vertebrates
Megaloptera—Dobsonflies, alderflies -Life History
a. holometabolous
b. larval life 2-4 years, adult life a few weeks
c. last instar larvae leave water, build a pupal cell in mud or old log and pupate.
d. Adults totally aerial–lay eggs in cases over water- hatchlings drop into water and begin life
e. Adults are very large and conspicuous
H. Trichoptera–caddis flies
1. General Features
a. larvae worm-like but with insect legs and many have highly sclerotized heads, dorsal shields on thorax, terminal sclerotized prolegs
b. many have abdominal gills
c. adults resemble moths (have scales on wings) but fold wings tent- like over the back and have very long antennae
Trichoptera–caddis flies- Ecology
a. widespread in most freshwater habitats, some semi-terrestrial, some are commensals with estuarine crustaceans
b. extremely diverse group with respect to functional feeding group: herbivores, detritivores, predators
c. frequently most numerous and most productive invertebrates in streams thus extremely important in stream food webs
d. many construct protective cases of materials ranging from silt to pebbles. many are silk-net spinners–show close affinity to Lepidoptera(moths & butterflies)
Trichoptera–caddis flies-life history
a. holometabolous
b. larval life 8-10 months, pupae & adults relatively short-lived
c. adults appear to produce pheromones for sex attractants again showing relationship to Lepidoptera
d. last larval instar constructs silken pupal case, molts into pre-pupa, which then molts into pupa in the water.
e. Emerging adult leaves pupal case in water and must swim to and break thru the surface film.
f. females lay eggs under water, then die
I. Coleoptera–beetles
1. General Features
a. larvae take many forms–some resemble megalopterans, others resemble caddisflies.
b. larvae characterized by heavily sclerotized head with sickle-shaped mandibles
c. adult forewing modified as elytra (hard shell) that covers hind wing
a. widespread in all aquatic habitats including caves, hot springs brine pools
b. larvae include: predators, scrapers, detritivores; adults same
c. adults of most species remain in the water almost full time but can fly and are often attracted to lights
d. many adults have defensive glands that protect them from predation, but beetles are still important in food webs
e. beetles are the most diverse of the insect orders on land and in the water–it is difficult to make generalizations that apply to all groups
Coleoptera–beetles – life history
3. Life History
a. holometabolous
b. most larvae require 6-10 months to mature. last instars leave water and construct a pupal cell on land.
c. most adults probably do not live very long in nature but can be kept alive in for years in the lab
J. Diptera–true flies
1. General features
a. larvae are legless and worm like–called maggots
b. adults take many forms but the presence of 1 pr wings sets them apart from all other insects
Diptera–true flies–Ecology
a. dipteran larvae are found virtually everywhere in freshwater; many are estuarine and many are adapted to living in hypersaline waters like the Great Salt Lake and the Dead Sea
b. adults are aerial creatures, many display complex mating behaviors
c. dipteran larvae run the full range of functional feeding groups in aquatic habitats including cannibalism and parasitism
d. adults range from DOC feeders to sucking vertebrate blood
e. larvae of certain groups e.g., Chironomidae, are often numerous under polluted conditions and are considered tolerant in general.
f. dipteran larva & adults are almost always very important in the tropic dynamics of habitats they occupy
Diptera–true flies–Life History
a. holometabolous
b. most go thru 4 or 5 larval instars, construct a pupal case, and pupate in the water or damp habitats.
c. some may pass from egg to egg in about 3 weeks and can have 5-10 generations per year; other have a single generation that lasts 6 months