zooplankton. zooplankton planktonic animals can be found in almost all animal phyla most...

ZooplanktonZooplankton


Planktonic animals Planktonic animals can be found in can be found in almost all animal almost all animal phylaphyla

Most zooplankton Most zooplankton belong to 3 major belong to 3 major groups: groups: rotifers, rotifers, Cladocera, Cladocera, andand CopepodaCopepoda


One other group may, One other group may, at times, be at times, be important: important: ProtozoaProtozoa

Spend only portion of Spend only portion of lives in plankton lives in plankton (mostly sediment-(mostly sediment-dwelling)dwelling)

Feed on bacteria, Feed on bacteria, detritus (little used by detritus (little used by other zooplankton)other zooplankton)

RotifersRotifers

Mostly littoral, sessile, Mostly littoral, sessile, but some are but some are completely planktoniccompletely planktonic

May be dominant May be dominant zooplankton in some zooplankton in some lakeslakes

Omnivorous, small Omnivorous, small (<12 µm)(<12 µm)

Filter-feeding with Filter-feeding with coronacorona

RotifersRotifers

Some are Some are predatorypredatory

AsplanchnaAsplanchna Feed on protozoa, Feed on protozoa,

other rotifers, small other rotifers, small crustaceanscrustaceans

Rotifer ReproductionRotifer Reproduction

Reproduction during Reproduction during most of growing season most of growing season by diploid female by diploid female parthenogenesisparthenogenesis

DiploidDiploid eggs produced eggs produced via via mitosismitosis

Develop into Develop into amicticamictic femalesfemales

Continues for Continues for generations during generations during good conditionsgood conditions


Environmental Environmental stress causes stress causes changeschanges Drop in temperatureDrop in temperature Crowding (food)Crowding (food) Accumulation of Accumulation of

pheromones from pheromones from femalesfemales

Reduced availability of Reduced availability of food components food components (e.g., vitamin E)(e.g., vitamin E)


MicticMictic females females develop, produce develop, produce haploid eggs via haploid eggs via meiosismeiosis

Unfertilized eggs Unfertilized eggs develop into malesdevelop into males

Mate with mictic Mate with mictic females to produce females to produce thick-walled thick-walled resting resting eggseggs


Resting eggs Resting eggs resistant to adverse resistant to adverse environmental environmental conditionsconditions

Eggs remain in Eggs remain in diapausediapause until return until return of favorable of favorable conditionsconditions

Hatch into Hatch into amicticamictic femalesfemales

Rotifer Population DynamicsRotifer Population Dynamics

Different species exhibit different population Different species exhibit different population peakspeaks

Some in early summer, others in winter/early Some in early summer, others in winter/early spring, others multiple times in summerspring, others multiple times in summer

Rotifer CyclomorphosisRotifer Cyclomorphosis

Seasonal Seasonal polymorphismpolymorphism

Elongation, Elongation, enlargement or enlargement or reduction, reduction, production of production of spinesspines


Reduce sinking Reduce sinking rate in warmer rate in warmer waterwater

Cope with larger Cope with larger preyprey

Better resist Better resist predationpredation

Brachionus


Spines prevent Spines prevent ingestion of ingestion of BrachionusBrachionus by by AsplanchnaAsplanchna

Formation of spines Formation of spines induced by organic induced by organic substance substance ((kairomonekairomone) produced ) produced by predatorby predator

Rotifer Use by FishRotifer Use by Fish

Too small to be Too small to be important as food for important as food for most fishmost fish

May be important in May be important in diets of some larval fishdiets of some larval fish

Rotifers are potential Rotifers are potential prey for predatory prey for predatory copepodscopepods

Vertical migration Vertical migration upward at midday to upward at midday to avoid copepodsavoid copepods

CladoceraCladocera

Small crustaceans Small crustaceans (0.2-3.0 mm) with (0.2-3.0 mm) with head, and body head, and body covered by bivalve covered by bivalve carapacecarapace

Swim by using large Swim by using large 2nd antennae2nd antennae

Filter phytoplankton, Filter phytoplankton, detritus for food detritus for food (some are predators)(some are predators)

CladoceraCladocera

Size of phytoplankton Size of phytoplankton ingested proportional to ingested proportional to body sizebody size

Rate of filter feeding Rate of filter feeding increases with size and increases with size and temperaturetemperature

Selective filtering by Selective filtering by cladocerans can cladocerans can remove big “chunks” of remove big “chunks” of the phytoplankton, and the phytoplankton, and alter phytoplankton alter phytoplankton successionsuccession

Cladocera ReproductionCladocera Reproduction

Reproduction similar Reproduction similar to that of rotifersto that of rotifers

ParthenogenesisParthenogenesis by by diploid females diploid females throughout most of throughout most of the growing seasonthe growing season

Continues until Continues until interrupted by interrupted by unfavorable unfavorable conditionsconditions


Temperature Temperature reductions, drying, reductions, drying, reduced reduced photoperiod, photoperiod, crowding crowding (competition for (competition for food), decrease in food), decrease in food size/qualityfood size/quality


Some eggs develop Some eggs develop into diploid malesinto diploid males

Females produce Females produce haploid eggshaploid eggs

Mate with malesMate with males Fertilized eggs Fertilized eggs

overwinter in overwinter in thickened brood thickened brood pouch - pouch - ephippiumephippium


Ephippia can Ephippia can withstand severe withstand severe conditionsconditions

Can be transported Can be transported by birds to other by birds to other waterswaters

Hatch under Hatch under favorable conditions favorable conditions into parthenogenetic into parthenogenetic femalesfemales

Population DynamicsPopulation Dynamics

Similar to those of rotifersSimilar to those of rotifers Some overwinter as adults, others as resting Some overwinter as adults, others as resting

eggs (ephippia)eggs (ephippia) Increased food and temperature enhance Increased food and temperature enhance

productionproduction

Diurnal Vertical MigrationsDiurnal Vertical Migrations

Most migrate to surface at dusk, downward at Most migrate to surface at dusk, downward at dawn (light intensity the stimulus)dawn (light intensity the stimulus)

Movements may be >50 m and rapid (20 m/hr)Movements may be >50 m and rapid (20 m/hr)

Diurnal Vertical MigrationsDiurnal Vertical Migrations

Reasons for migration:Reasons for migration: 1) avoid visual feeding fish in epilimnion by 1) avoid visual feeding fish in epilimnion by

coming up to feed on phytoplankton after darkcoming up to feed on phytoplankton after dark 2) improve food utilization - filter faster in warmer 2) improve food utilization - filter faster in warmer

water, assimilate better in cooler waterwater, assimilate better in cooler water

Cladoceran CyclomorphosisCladoceran Cyclomorphosis

Extension of head to Extension of head to form helmetform helmet

Increase of caudal Increase of caudal spine lengthspine length

Caused by increased Caused by increased temperature, temperature, turbulence, turbulence, photoperiod, foodphotoperiod, food

Cladoceran CyclomorphosisCladoceran Cyclomorphosis

Advantage of allowing Advantage of allowing for continued growth for continued growth of transparent of transparent peripheral structures peripheral structures without enlarging without enlarging central portion of central portion of body visible to fishbody visible to fish

Reduces predationReduces predation

Food for Fish!Food for Fish!

Large species favored Large species favored by many fish (visual by many fish (visual and filter-feeders)and filter-feeders)

More energy return More energy return from bigger speciesfrom bigger species

Eliminates large Eliminates large forms, small ones forms, small ones flourish (big forms flourish (big forms often predatory)often predatory)

CopepodaCopepoda

Microcrustaceans in Microcrustaceans in same size range as same size range as cladoceranscladocerans

Several different Several different groups based on groups based on differences in body differences in body structurestructure

2 major groups: 2 major groups: cyclopoidscyclopoids and and calanoidscalanoids

CopepodaCopepoda

CyclopoidsCyclopoids - short - short 1st antennae1st antennae

CopepodaCopepoda

CalanoidsCalanoids - long - long 1st antennae1st antennae

CopepodaCopepoda

CyclopoidsCyclopoids - most - most are littoral, but few are littoral, but few are open-water are open-water planktonic formsplanktonic forms

All seize food All seize food particles and bring particles and bring them to mouth - them to mouth - raptorialraptorial

CopepodaCopepoda

Most are predators Most are predators (eat zooplankton), (eat zooplankton), but some are but some are herbivores herbivores (phytoplankton)(phytoplankton)

Move by swimming Move by swimming with legswith legs

CopepodaCopepoda

CalanoidsCalanoids almost almost strictly open-water strictly open-water planktonic, seldom planktonic, seldom in littoral areasin littoral areas

Primarily filter Primarily filter feeders on algae, feeders on algae, detritus (filtering detritus (filtering appendages near appendages near mouth - maxillae)mouth - maxillae)

Copepod ReproductionCopepod Reproduction

No parthenogensisNo parthenogensis Both males, Both males,

females presentfemales present Sexual Sexual

reproduction reproduction always presentalways present

Fertilized eggs Fertilized eggs carried attached to carried attached to female’s abdomenfemale’s abdomen


Eggs hatch into Eggs hatch into nauplius larvaenauplius larvae - 3 - 3 prs. of legsprs. of legs

Grow and molt Grow and molt several times to several times to become become copepoditecopepodite

Grow and molt Grow and molt more before more before becoming adultbecoming adult


Longer period of Longer period of time from egg to time from egg to adult than in adult than in rotifers, rotifers, cladoceranscladocerans

May have resting May have resting eggs (overwinter), eggs (overwinter), or diapause in egg or diapause in egg or copepodite or copepodite stagestage

Community DynamicsCommunity Dynamics

Predation by Predation by cyclopoid cyclopoid copepods may copepods may kill up to 30% of kill up to 30% of nauplii or nauplii or copepodites (of copepodites (of own or other own or other species)species)


This predation This predation may result in may result in vertical, vertical, seasonal seasonal separation of separation of similar speciessimilar species


Same diurnal Same diurnal vertical vertical migrations as migrations as cladoceranscladocerans

No No cyclomorphosiscyclomorphosis

Great as fish Great as fish food!food!

Zooplankton GeneralitiesZooplankton Generalities

Assimilation Assimilation efficiency ~50%efficiency ~50%

Increased with Increased with higher temps.higher temps.

Decreased with Decreased with increased food increased food availabilityavailability


Highest Highest assimilation when assimilation when feeding on prime feeding on prime food - right type, food - right type, sizesize

Lower when Lower when feeding on bacteriafeeding on bacteria

Lowest when Lowest when feeding on detritusfeeding on detritus


Seldom evenly Seldom evenly distributeddistributed

Avoidance of shoreAvoidance of shore At mercy of At mercy of

epilimnetic water epilimnetic water movements, movements, especially especially Langmuir spiralsLangmuir spirals


Productivity Productivity correlated with correlated with phytoplankton phytoplankton productionproduction

Filter-feeders have Filter-feeders have higher productivity higher productivity than predatorsthan predators


Many zooplankton Many zooplankton abundant in littoral abundant in littoral areasareas

Associated with Associated with macrophytes, macrophytes, sedimentssediments

Abundance related to Abundance related to plant surface area, plant surface area, algal/detrital algal/detrital abundanceabundance


Abundance Abundance generally highest in generally highest in spring and fall, spring and fall, lowest in mid-lowest in mid-summersummer

Lows correspond Lows correspond with heavy with heavy predation by insect predation by insect larvae, small fishlarvae, small fish

zooplankton. zooplankton planktonic animals can be found in almost all animal phyla most...

Documents

copepoda slide

food slide

predation slide

calanoids slide

adult slide

predatory slide

mhr slide

raptorial slide