What do you do when you find an
unknown invertebrate?
a) squish it
b) call Homeland Security Department
c) use a dichotomous key to identify it
Rotifers


~1500 species, size between 0.04 and 2.5 mm
Generation time is a few days (temperature dependent)



Most are filter-feeders



Can tolerate lower Water Residence Time than larger
Corona
zooplankton
Populations respond quickly to an increase in food resources
Use corona to create feeding current
A few are predaceous (Asplanchna)
Prey species may exhibit cyclomorphorosis
www.tolweb.org/tree/ToLimages/cava042p.jpg
Asplanchna
www.microscopy-uk.org.uk/mag/artfeb02/fresh/freshimg/rotifers.jpg
cyclot.hp.infoseek.co.jp/wamusi/mituude1.jpg
Annelida: Oligochaeta
Bilaterally symmetrical
Segmented coelomates, each segment
w/ chaetae (little hairs/bristles)
http://www.inhs.uiuc.edu/~sjt
aylor/cave/oligochaeta.html
Hermaphroditic; sexual and asexual reproduction.
Usually paratomy (budding), also create cocoons filled
with embryos.
Wide spread, many habitats and trophic levels
Some spp used as pollution indicators- very tolerant
Bioturbators
Annelida: Hirudinea (leaches)
Dorsoventrally flattened &
segmented
Mouth surrounded by oral
sucker, parasites, scavengers
and predators
Only 2 common U.S. genera
that attack humans; sufficient
blood taken so that leach may
be 5 times original mass
http://www.nanfa.org/akiweb/658.JPG
Used to support large industry in Europe during 18th and 19th centuries for
medicinal purposes
Hirudo medicinalis raised in ponds in large numbers (has been introduced to
NA several times but unsuccessful)
http://www.nytimes.com/2006/02/07/science/07leec.html
Famous invertebrates from Hollywood!
Arachnida: Hydrachnidia,
water mites
Look like tiny spiders, 6 legs
Most carnivorous or parasitic
Separate males and females
Can be very abundant in weedy
areas, usually found in shallow
waters
Beautiful colors (fade w/
preservative)
Hard to identify
http://images.google.com/imgres?imgurl=http://test.dnr.nsw.gov.au/care/
wetlands/facts/paa/invertebrates/images/water_mite_eylais.jpg&imgrefurl
=http://test.dnr.nsw.gov.au/care/wetlands/facts/paa/invertebrates/watermi
tes_aquaticspiders.html&h=338&w=400&sz=20&hl=en&start=14&sig2=eK
Oanf2HjZpwetS9dOHqEA&tbnid=Mqsx3hWcSPtdEM:&tbnh=105&tbnw=12
4&ei=OQEiR5adKaeceMq70KIC&prev=/images%3Fq%3Dwater%2Bmite%2
6gbv%3D2%26svnum%3D10%26hl%3Den
Phylum Mollusca
(Life in a shell)
>100,000 spp.
Gastropods-snails & slugs
Bivalves- clams/mussels
Cephalopoda (squids, octapus, cuttlefish,
nautilus- marine)
Higher taxonomy messy
You name it, some gastropod does it
70% of all mollusks
marine, freshwater and terrestrial habitats.
About 500 species in the freshwaters of North America,
north of Mexico:
350 prosobranchs (derived from marine)
gill (ctenidium)
operculum
150 pulmonates (derived from terrestrial)
lung=modified mantel cavity
Valvata bicarinata
Campeloma decisum
Physella/Physa spp.
http://members.aol.com/mkohl1/FWshells.html =picture source
Consider a snail & leech of about same tissue mass.
What is the primary physical diff between them?
How does this diff affect their predators & where they live.
What affects their habitat choice more- trophic level or
potential predators?
superfamilies
Bivalves
NA bivalve fauna most diverse in word
Unionoidea ~278 spp
Corbiculacea 36 native and 4 introduced
Dreissenoidea 2 spp (zebra and quagga mussels)
(more later)
Mucket
Crustaceans
Specious, abundant and ecologically important
>35,000 species mostly marine, some fw & terrestrial
-anatomically diverse--fused segments or specialized
appendages
-important trophic component of many systems
Crustaceans have:
-2 pairs of antennae
-most body segments bear paired, jointed appendages
-all crustaceans go through a free nauplius stage or
show evidence of an egg-nauplius stage
Branchiopods
•
Most are filter feeders
– feeding appendages act as
electrostatic filters
– Feed on phytoplankton, bacteria,
protozoa
•
•
•
Often the dominant herbivores in
lake systems (before zebra
mussels)
Generation time is a few weeks
Some are predators on other
cladocerans and rotifers
(Leptodora, Bythotrephes)
webs.lander.edu/rsfox/rsfoximages3/clad99L_x550_x_643x.gif
Bosmina
Leptodora
www.cof.orst.edu/project/plankton/bos.jpg
/www.internal.eawag.ch/~steiner/Zoo/Bilder
Bythotrephes
www2.biologie.uni-halle.de/zool/dev_biol/lect/pk_lim/limno/Daphnia.jpg
Male Daphnia
First
antennae
•
Branchiopods are usually parthenogenetic
–
•
Sexual reproduction can be triggered by
–
–
–
•
Produce eggs (clones) after each molt (~3-30
eggs)
Low food condition
Decreasing photoperiod
Overcrowding
Resting eggs are contained in an Ephippium
–
–
Can be dried, transported on legs of waterfowl
Eggs from Ephippia buried in sediments can
survive decades
Ephippium with 2
resting eggs
Copepods

Three major groups: Cyclopoida, Calanoida, (pelagic) and Harpactocoida
(benthic)


Always sexual reproduction, near equal numbers of
males and females
Cyclopoids

Life Cycle
•
•
•
•
Shorter generation time (1-2 months)
Eggs hatch as nauplius larvae
Several juvenile molts (copepodids) before becoming adults
Juvenile stage may enter diapause in fall and re-activate in the spring
Adult male
http://www.emporia.edu/biosci/
invert/lab6/copnaup1.jpg
centexnaturalist.com
Adult female
Female with egg sacs
Copepods

Calanoids

Life Cycle
•
•
•
•
Longer generation time (6 months or more)
Eggs hatch as nauplius larvae
Several juvenile molts (copepodids) before becoming adults
No diapause
Adult female
www.glerl.noaa.gov
www.sahfos.ac.u
www5.pbrc.hawaii.edu
Adult male
Avoidance of Predation

Cyclomorphosis

Daphnia and others may grow long helmets and tail spines
(inducible defenses) to help avoid invertebrate predators
www.unb.ca
www.nature.com
www.esf.edu/efb/schulz/Art.html
Cyclomorphosis

Why not have long spines and helmets all the time?


Energetically expensive, lowers reproductive rate
Interferes with feeding in some cases (Bosmina)
www.ecostudies.org/images
www.fbl.ku.dk
Avoidance of Predation

Escape Tactics

Calanoid copepod “jump” reaction
• Flex 1st antennae to achieve burst of speed, acceleration up to 30G
and 100 body lengths/second

“Dead Man” response
• Some small cladocerans (Bosmina, Diaphanosoma) may avoid
detection by invertebrate predators by stopping all activity and
allowing themselves to sink slowly
Bosmina
www.microscopy-uk.org.uk
Diaphanosoma
www.glerl.noaa.gov
Epischura
www.lbm.go.jp/emuseum
Avoidance of Fish Predation

Diel (Daily) Vertical Migration
(DVM)



Most zooplanktivorous fish are visual
predators that feed during the day.
Larger zooplankton species typically
migrate downward during the day to
avoid being seen by fish
Migrate upward at night to feed on
algae near the surface, more
dispersed at night
www.wellesley.edu
Avoidance of Fish Predation

Try to be as transparent as possible

Especially true for large invertebrate predators (Chaoborus,
Leptodora) and slow-moving species (Daphnia, Bosmina, etc)
Leptodora
Chaoborus
“Phantom midge”
www.lbm.go.jp/emuseum
www.internal.eawag.ch
www.microscopy-uk.org.uk
Order Anostraca; fairy shrimp
temporary pools or very saline
habitats (e.g. brine shrimp:
Artemia salina)
swim on backs by beating
appendages; also serves to
obtain food
either sexual or parthanogenic
eggs; make resting eggs that
can hatch out when put in water,
“sea monkeys”
http://www.cdpr.ca.gov/docs/es/esgifs/fairy.gif
How do the defense strategies of pelagic and benthic
animals differ?
Why?
Order Isopoda (aquatic sow bugs)
most spp. marine or terrestrial; 130 f.w. spp. in N.A.
flattened dorsoventrally
scavengers
males carry females before mating, waiting for preadult
exoskeleton shed
 bilateral copulation (e.g. first one
side then the other); after mating
female sheds anterior half of
exoskeleton so that brood chamber
plates are functional; fertilized eggs
and young stay in brood chamber,
young find their way out the
posterior end by trial and error.
http://www.iii.to.cnr.it/limnol/bentos/foto/Asellus_aquaticus.jpg
Order Amphipoda (superorder Pericarida, scuds)
laterally compressed
crawl or swim
respiration through gills
usually benthic some “dart” into pelagic zone
omnivorous scavangers; will eat dead
animals, leaves, organic debris and graze
surface films
male carries female until she molts
(amplexus), they separate briefly and rejoin to copulate, shortly thereafter the
female ovulates and oviposits; eggs and
developing young reside in the
marsupium, young are released at the
females next molt
http://www.nativefish.org/Gallery
/other/Gammarus-sp..htm
Fresh water Insects
When J. B. S. Haldane, a British geneticist, was
asked what his studies of nature revealed about God,
he replied, "An inordinate fondness for beetles."
5 aquatic orders, almost all spp have aquatic larvae
Ephemeroptera
Odonata
Plecoptera
Trichoptera
Megaloptera
5 partially aquatic orders, most species are terrestrial,
but some spp have aquatic life stages
Heteroptera
Coleoptera
Diptera
Lepidoptera
Neuroptera
Ephemeroptera: mayflies
~675 spp
Streams and littoral areas of lakes
Important fish food
Usually 3 caudal filaments
Abdominal gills
http://www.waterbugkey.vcsu.edu/php/orderdetails.php?idnum=8
Adults do not feed
Females oviposit usually at water surface
Burrowing mayflies (Hexagenia) important species in
western Lake Erie
Mating
swarm near
Sandusky
River
Collecting females at Windsor
http://www.heidelberg.edu/depts/wtr/krieger.html
Odonata
Anisoptera: dragonflies
Zygoptera: damselflies
~434 spp
Most larvae in lentic (lake or slow water) habitats
Larvae large and predatory
Elongate hinged labium
1-6 yrs
http://www.naturewatch.ca/eman/rep
orts/publications/99_montane/odona
ta/odonatafig06.html
http://www.entomology.umn.edu/museum/links/coursefiles/Odonate%20characters.html
Plecoptera: stoneflies
~614 spp
Most common in fast, cold streams
Larvae predators
2 long tail filaments
Long antennae
Larvae crawl rather than swim
Adults live days to weeks
http://www.weeksbay.org/newslet
ter/Sum_2003/Pg8_1.htm
Trichoptera: Caddisflies
http://www.wildscape.com/earrings.asp
~1400 spp
Lotic & lentic
Adults terrestrial and easily identified, but
many larvae unknown
Some build silk nets to catch prey
Some free living predators
Some build cases
http://www.nativefish.org/G
allery/other/Caddisfly.htm
Can be dominant in streams
Many fish feed on larvae
Can have large hatches
http://www.epa.gov/bioindicators/html/caddisflies.html
Megaloptera: fishflies and alderflies
7-8 lateral filaments (O2 uptake) & large mandibles
Can be confused with Coleptera
Adults, large, secretive &
terrestrial
Lentic larvae have caudal
respiratory tubes
Larvae are predators
Corydalidae
http://www.epa.gov/bioindicators/
html/photos_invertebrates.html
5 aquatic orders, almost all spp have aquatic larvae
Ephemeroptera
Odonata
Plecoptera
Trichoptera
Megaloptera
5 partially aquatic orders, most species are terrestrial,
but some spp have aquatic life stages
Diptera
Coleoptera
Heteroptera
Lepidoptera
Neuroptera
Diptera: flies & midges
Many families and spp
Differ greatly in ecology (habitat – feeding…….)
Only larvae are aquatic
Lack segmented thoracic legs
Trophic importance in many systems
Some vectors of disease (e.g. mosquitoes)
Chironomidae: midge larvae (+ 2000 spp)
Very important fish
food
Wide range of
ecology
http://www.biol.wwu.edu/4
07/407/Crustaceans.html
Tipulidae: cranefly larvae
http://alpaca.cs.umb.edu/gal
lery/AquaticInvertebrates/tipulidD_thm
Chaoboridae: phantom
midge larvae
Pelagic predators
http://www.iii.to.cnr.it/limno
l/bentos/cauborus.JPG
Coleoptera: beetles
Only 3% of beetles have aquatic stage (still many spp!)
1450 in NA
Spp w/ aquatic larvae and adults
http://www.ru.ac.za/acad
emic/departments/zooent
o/Martin/elmidae.html
“water pennies”
Larvae aquatic, adult riparian
http://dnr.state.il.us/or
ep/ecowatch/RIVER/
bugs/page1.htm
Whiligigg beetles
Adults and larvae aquatic
http://academic.emporia.edu
/aberjame/wetland/wildlife/w
ild24.jpg
Heteroptera: true bugs
Gerridae: water striders
Aquatic larvae and adult
http://www.inhs.uiuc.edu/~
sjtaylor/gerromorph/strider
s.html
Predators
Notonectidae: backswimmers
Sucking predators
Creepy!!
Belostomatidae: giant waterbugs
Voracious predators
Adults can fly
In some spp males
carry eggs on back
http://creatures.ifas.ufl.edu/misc/bugs/belo
stomatid01.htm
http://www.agls.uidaho.edu/ento/Si
xleggedWonders/insects_of_idaho/
hemiptera.htm
Things zoobenthos can eat: location and quality
-Floating
plankton: phyto, zoo, seston
stream drift: animal or detritus
-On a surface (moving or still water)
plant: low quality
algae: on sediment, rock, plant
animal: probably hiding
detritus: very low quality, but doesn’t hide,
associated microbes = good food
Balance of algae-animal-microbe-detritus affects C:N:P
ratio. In general high N & P = good food.
Relatively few benthic inverts eat live macrophytes.
Why?
Duarte, C.M. 1992. Nutrient concentration of aquatic plants: pattern
across species. Limnol & Oceonog 37:882-889
So why are the invertebrates in the littoral zone if they don’t eat the plants?
pelagia
high benthos
density & diversity
low benthos
density & diversity
See 24.5
Take home points
--Benthos are much more diverse (and interesting ) than
zooplankton
--Humans tend to study larger size classes
--Many different feeding modes
--Richness and abundance highest in litoral zones,
associated with macrophytes or other structures
--Often important energy source to fish