PROTOZOAAND OTHER PROTISTS
CLADOCERANS AND COPEPODS
LIPIDS IN ZOOPLANKTON
ZOOPLANKTON IN LENTIC,LOTIC ECOSYSTEM
LARVAL FORMS OF ARTHROPODS
They drift,float,weekely swim in the water.
The name plankton comes from the Greek word PLANKTON which means WANDERER
Zooplankton are heterotrophs.
Zooplankton found in lakes,streams and swamps.
Many species move into shallower waters at night.
Dominant among the larger organisms are cladocerans which swim by rowing with large antennae.
The smallest zooplankton are eaten by larger zooplankton.
• Adaptations of zooplankters to the aquatic habitat include rapid
reproduction,small size and spine formation.
• Temporary drying out or freezing of water bodies affect zooplanktons.
• Cladocerans and rotifers tend to be more abundant in summer,probably due
to the greater availability of food.
• Copepods and opossums shrimps are generally perennial with active over
• Zoobenthos spend their life in sediments.
• Single lake contains few species of cladocerans,copepods and rotifers.
• Large zooplankton dominate when zooplanktivorous fish are absent but may soon be
eliminated if predators are introduced.
• Exception may occur if large size is due to spines or other features which are invisible to
• In deep lakes zooplankton may be seggreted at different levels during the day. Most
respond to changes in light intensity by migrating upward in the evening and downward
• The downward movement may be passive sinking or active swimming away from light.
• During thermal stratification strong swimmer pass through the thermocline to graze in
the epilimnion during the darker hours which reduced danger from predators.They then
return to the cooler hypolimnetic water by day.
• The nutrients in a particular water layer may be increased by zooplankton
excretion and lower rates of nutrient uptake due to reduced number of algae.
• Excretion of ammonia and orthophosphate – euphotic zone –primary
production-constitute substantial fertilization.
• Planktonic animals – dominated by four major groups:
• (a) PROTISTS
• (b) ROTIFERS
• (c) CLADOCERANS
• (d) COPEPODA
• Free living protists –
ciliates, flagellates and
• Protistan zooplankton-
organic carbon utilization
and nutrient cycling.
DYNAMICS OF PROTISTAN ZOOPLANKTON
• These are abundant component of zooplankton.
• Feed on bacteria and fix carbon photosynthetically.
• Common form include dinofalgellates. e.x . Ceratium and peridinium.
• The heterotrophic flagellates –two
types based on size,
(a) heterotrophic nanoflagellates (
(b) large heterotrophic flagellates( >
• Among both temperate and
subtropical lakes dinoflagellates tend
to increase in dominance as the pH of
the water decreases and can dominate
in the acidic lakes.
• Protists possess variety of nutritional mechanisms that include autotrophy and
heterotophy.Heterotrophic mode consists of ,
(a) uptake and assimilation of dissolved organic compounds.
(b) feeding directly on living or dead particulate organic matter.
(c) metabolic exchange with endosymbionts.
• Food capture by filtration – direct encounter and filtration in benthic flagellates by
• Factors influencing rates –size and velocity – feeding rates directly correlated with temperature.
• Two species of benthic ciliates of the genus loxodes were studied in a shallow eutrophic lakes in
relation to feeding and digestion of algae. Feeding rates were low –negatively hypolimnion to the
• Major ciliate genera –freshwater protozooplankton –across spectrum of trophical
• E.x. oligotrichs ( strombidium and halteria) found world wide in lakes across the
• Tinintinnid ciliates –widely distributed.
• Haptorid ciliates distributed abundantly.
• Feed on bacteria,algae and detritus, some are carnivorous and feed on small
• Ciliates – more significant of eutrophic lakes.
• In eutrophic lakes-modest average
• HPoorly represented in the
zooplankton of freshwaters.
• eliozoans –restricted vertically to
epilimnion and metalimnion of
• In late spring sarcodines- reduces
density-by –formation of fat
inclusions and gas bubbles.
• Protozoa and other protists – aerobic
and some grow at low conc. of oxygen.
• Four distinct types of protozoa –
vertical distribution .
(a) specialized anaerobic ciliates-
inhabit hypolimnion( e.x. saprodinium).
(b) microaerophilic ciliates – inhabit
metalimnion ( e.x. loxodes).
(c) ciliated protozoa ( e.x. frontonia)
inhabit metalimnion of eutrophic lakes.
(d) epilimetic ciliates (e.x.
• Rotifers –wide range of morphological
• Sessile,planktonic and non predatory
– omnivorous feeding by ciliary
• Predatory species –Asplanchna are
large and prey upon protozoa.
• Most rotifers are not planktonic –
sessile –inhabit litthoral substrata.
• Feed – sedimentary particles-mouth orfice –by coronal cilia. Food particles size less
than 12ʮm in diameter.
• Asplanchna prey upon algae,small crustaceans.
• Food limitations to growth of rotifers vary widely.Threshold conc. – high –to their
• Several mechanism regulate the ingestion of suspended particles.
(a) cirri of pseudotrochous
(b) buccal field
(c) oral canal
• Asplanchna ,best studied by Gilbert and his co-workers .
• Produced by amictic females.
• Increasing population density – extraordinary levels of crowding produced no
mictic females .
• Algal cells has to be eaten to induce the reproductive change in
ASPLANCHNA,extracellular products would not induce the change .
• Dietary component – plants was d-ά-tocopherol(vit-E) –transmission from the
parthenogenetic to sexual reproduction – spermatogenesis or male fertility.
• Mictic female offspring- larger and change in morphology.
ASPLANCHNA –increases when
herbivorous zooplankton are more
Increases contacts between males and mictic
females facilitates –resting eggs.
Temperature – influences –rates of
Other factors affect natural population but
temperature a major factor affecting birth
• In freshwater crustacea-dominated almostly by the cladocerans and copepods.
• Only a few insects are planktonic in immature stages.(e.x. chaoboros) –notable example .
• A few species of cypria are apparently partly planktonic.
• The freshwater brachiopoda (fairy and clam shrimps)- inhabitants of shallow lakes.
• THE TADPOLE SHRIMP (Notostraca) – benthic –shallow lakes ,temporary lakes of arid
• FAIRY SHRIMPS lacking a carapace and CLAM SHRIMPS compressed laterally –in
shallow lakes of semi arid regions.
• In semipermenant lakes – humid regions,hatching and reproductive rates are high –
related to temperature.
• The suborder Cladocera includes
microzooplankton –size-0.2 to 0.3mm.
• Has distinct head –body –covered –
• Light sensitive organs –large
,compound eye,smaller ocelli.
• Has swimming appendages.
• Mouth parts –large chitinized
mandibles ,pair of maxillus ,mandibles
• Usually have five pairs of legs-attached to
the ventral part of the thorax.
• Legs-flattened –bear numerous hairs and
• Food particles filtered by setae-between
the bases of the legs –mixed with oral
• Litthoral CHYDOIRID cladocerans –
modified legs-prehensile in scraping up
larger pieces of detrital material.
• Common cladocerans POLYPHEMUS
and LEPTODORA-predaceous –feed-
seizing large particles –protozoa ,rotifers
and small crustaceans by prehensile legs.
• Cladocerans –parthenogenetic-until sexual reproduction-females preduce eggs that
develop into more parthenogenetic females.
• Increases in temoerature –increase in molting,brood production .
• Increase in food supply-increase survivorship and fecundity.
• Male production correlated with crowded and a rapid reduction n food supply-low
food-inhibits reproduction-males –smaller-slight morphology from females.
• Short day photoperiods (12h light and 12h dark)-increased production of Daphnia
• Photoperiod response must vary among species.
• Body –anterior metasome divided into head
regions –five pairs of appendages.
• Has antenna –thorax with swimming
segments-first in females modified as genital
segments and terminal caudal rami bearing
• Harpactinoid copepods-litthoral-
• Cyclopoid copepods – primarily litthoral
benthic species-predominantly planktonic-in
small shallow lakes.
• Calanoid copepods –exclusively planktonic.
FEEDING OF COPEPODS
• Mouthparts of Harpactinoids-seizing and scraping particles from sedimentation and
• No filtration mechanism-Cyclopoid.
• Maxillus –hold and pierce the food particles.Diatoms –digested,green algae –not
ruptured –moves to gut undigested.
• Many species –Macrocyclops, Acanthocyclops, cyclops and Mesocyclops – carnivorous.
• Food-microcrustaceans , dipterian larvae and oligochaetes.
• Herbivores cyclopoid –Eucyclops,Acanthocyclops and microcyclops.
• Food- algae and long strands of filamentous species.
• Carnivorous cyclops are larger than herbivorous cyclops.
• Food search by discontinuous ,irregular movements in the water / over the
• Herbivorous species employ-gustatory chemoreceptor organs-food seeking –
discriminate inorganic and organic particles .
• Locomotion –short,jerky swimming movements,animal-propel by rapid movement
• Swimming continuous in calatinoid copepods.
• Calanoid copepods do not strain particles out of the water-but –propel water by
flapping of four appendages.
• Selective feeding – calanoid copepods.
• Two closely related species-Diaptomus laticeps and Diaptomus gracilis –coexist in
lake,WINDERMERE , ENGLAND.
• Seperated by size differences –correlated with differences in food consumed.
• The larger D.laticeps –feed-Melosire ,smaller D.gracilis – minute spherical green
algae and detritus.
• FEEDING RATE: Is a measure of the quantity of food injested by an animal in a
given time measured in terms of number of cells ,volume,dry
weight,carbon,nitrogen or some other relevant aspect of the food that is ingested.
REPRODUCTION IN COPEPODS
• Some species reproduce throughout the year while others at specific times of the year.
• Copulation – male clasping the females –transfers spermetaphores-ventral side.
• Fertilization-immediately or several months after copulation.
• Reproductive cycle not affected by photoperiods.
• Small number of females carrying a few eggs for a short period at high temperature can
produce more young than many females with large egg cluthes that are exposed to long
periods at low temperatures.
• Copepods eggs hatch – develop- naupili-undergo subsequent larval stages.
• Time required to complete the juvennile stages and period of diapause is highly variable
among species and depend upon seasonal conditions.
Lipids in zooplankton
• Lipids –in zooplankton-dominant energy storage compounds-significant portion of dry
mass and dietary in origin.
• Type and amount of lipid contained –correlated directly with recent feeding activities
and food selectivity.
• Zooplankton –food limited-in summer months.Food availability low-lipids reserves-
essential survival for cladocerans embryos,neonates and adults.
• Lipid content-decreases-from spring to early summer,increase-late summer and autumn.
• High PUFA –critical to maintain high growth,survival and reproductive rates of
• High food quality algae –rich in PUFA content.
BIOTA OF LITTHORAL ZONE:
• Lentic life- more profilic in litthoral zone-can see great concentrations of animals-distributed in
• In or bottom –Dragonfly nymphs,cray fish,isopods,worms,snails and clams.
• Protozoans-Vorticella stentor ,larvae of dysticus , laccotrophes , glossophonia , climbing dragon ,
damsel fly , nymphs , rotifers , flatworms , bryozoa , hydra , snails.
• Larvae of chironomous –found-underneath of floating plants.
• Daphnia and free swimming fauna – Paramecium, Euglena , Ranatra , larvae of culex ,Gerris.
• Nektons –frogs,salamanders,snakes
• Neustons-whirling beetles,water spiders,top minnows and sun fish.
PARAMECIUM EUGLENA LARVA OF CULEX
BIOTA OF LIMNETIC ZONE
• Region of rapid variation with water level,temperature,oxygen
content varying from time to time.
• FAUNA: Macrobiotus , Rotatoria , Philodina occupies this zone.
• Sedentary and slow moving forms are excluded from this zone
because of predators and lack of permanent substratum.
• Limnetic zone has autotrophs in abundance.
BIOTA OF PROFUNDAL
• Deep profoundal zone contains bacteria , fungi , clams , blood worms (
larva of midges) annelids and other small animals capable of
surviving –little light and low oxygen.
• Main source of food in profoundal – detritus that drains out from the
• All organisms in this zone are heterotrophs.
• Larva such as phantom larvae and pea shell clam inhabits in this
• Lakes covered with sediment to
form a uniform substrate.
• Being a darkest region ,low
oxygen and low temperature plant
communities will be scarcely seen.
• Midges , burrowing mayflies ,
snails and tubeworms inhabit
mostly in this zone.
zooplankton OF LOTICECOSYSYTEM
A) RAPID FLOWING WATER:
• Water flow- rapid and turbulent.
• Organisms swept away by the water current
• Animals- cephalopteryx , Helodes, Phalocrocera ,Gammacus-live
among leaves and stems .
• Possess hook like structure- attachment.
• Larvae of simulids – present –exposed surface of plants.
(1) ROCK INHABITING FORM
• Animals- live on exposed rocks – efficient mechanisms-staying in one place.
• Organisms – usually flattened
• Freshwater limpets-flat-resistance to current –large and powerful.
• Larvae of riffle beetles and Bacthis larvae –not almost flat-legs-hooked claws –hold substrate
• Larvae of simulim and chironomids –cling –grappling hooks at posterior ends.
• Caddisfly worms –claws on legs and hooks at posterior end of the body.
• Mayfly nymphs – attach-functional pads,freshwater sponges-cement themselves –rocks surface.
• Organic detritus – washed –rapid water ecosystems from upstream and terrestrial areas.
• Mayfly and strong naids –
• Include thigmotaxis and
and has spines –attach to
the rocks during high
(3) INHABITANTS BENEATH THE ROCK
• Current-weaker-less likely carried away-lack special adaptations.
• Current –slow-fish will be present-stenothermal.(e.x.TROUT).
• Fishes in fast water ecosystems-streamlined body.
• TROUT-capable of moving against the current.
• Noemacheilus(small loaches) , Ambyceps olyra(loach like fishes)-met at the
• Limpets like fishes-Glyptosternum , Balitora,Garra-inhabits rocks.
• Loaches and carps –adhere to the rocks-Gastromyzon,Indian loach Balitora
• Physio-chemically –fast
flowing water-cold-deep lakes.
• Water temperature –
• Productivity-current-limits the
amount and type of autotroph
B)SLOW FLOWING WATER
• Flow-laminar-erosive power-reduced-has –sediment particles and decaying organic
matter-debris-deposited on the bottom.
• Slow streams –higher temperature-planktonic organisms-large numbers in the
• Zooplankton- sowbugs , sphaenuis , pisidium , anodonta dominate , damselfly
naiads,alderfly,nematodes,carps,cat fishes,fast water shrimps.
• Insects –water striders,water boatman.
• Bottom-mud contains organic materials than mineral fragments.
• Oxygen concentration- limiting factor-low level turbulence-less oxygen.
• Fishes –tolerate low oxygen levels .
• Drift-contains-small living organisms-bacteria,algae,detritus.
• Drift includes free floating invertebrates.
• Most stream dwellers –use bristles on their legs or mouthparts as filters and scrape off and eat the
particles they collect .
• Drift – complicated processs –exposure to predation complicate their feeding.
• Many insects-drift downward and emerge brief aerial existence fly back upstream to lay their eggs.
• Mayflies –live only a matter of hours after emergence which limits their flying range.
• Most predation-daylight-drift-in night.
• Insects –possess special adaptive structure –prevent them from being dislodged.
CYCLOMORPHOSIS IN ROTIFERS
Common change in growth form among rotifers:
• Elongation in relation to body width:E.x. Asplanchna –midsummer –population-about five
times –spherical morphology –late spring –sterile and die back –do not reappear-next spring.
• Enlargement:E.x. Asplanchna seiboldi –formation of body wall outgrowths or humps-caused
by tocopherol-adaptive response –large size food in summer.
• Reduction in size:E.x. Keretella –high temperature in summer-disappropriate reduction in
length of lorical spines.
• Production of lateral spines:E.x. Brochionus calciforus-posterior spines-elongate-large
rotifers-two pairs of anterior spines and one pair of posteromedian spines
CYCLOMORPHOSIS IN CLADOCERANS
• Seasonal polymorphism –conspicuous in cladocerans.
• E.x. Daphnia-studied by Hutchinson- increase water temperature,light and food in
the spring-extension of anterior part of the head to form a crest or helmet.
• Carapace length-decrease –spring and summer.Increase in autumn.
• Parthenogenetic eggs –increases in summer.
• Number of instars-increases with high temperatures.
• Head development and head shape –vary among species or same species with
different environmental conditions.
• Tropical and subtrophical lakes-no cyclomorphosis
• Cyclomorphosis in Bosmonia, Ceriodaphnia, Chydorus-much distinct than daphnia-
reduction-length of the body.
• Bosmonia-formation of transparent dorsal humps-no increase in length and
reduction in antennule length and number of segments.
• It is clear that temperature is the primary stimulus affecting the height of the head
helmets in Daphnia
• Food supply-affects specific growth.
• Water turbulence-significant factor and light-carapace increases.
• Organic substances –invertebrates especially by Chaoborus and fish predators –
induce cyclomorphic growth in Daphnia
CYCLOMORPHOSIS IN COPEPODS
• Seasonal polymorphism-minor in comparison with that found among
the parthenogenetic Cladocera and rotifers.
• Temperature – significant role.
• In few cases-animals of summer populatoins tend to somewhat
smaller than animals living in colder seasons.
• Earlier investigators –seasonal polymorphism-resistance to sinking-viscosity of
water decreases at high temperature
• Minimizes –predatory avoidance.
• Cyclomorphosis growth-body –small-less susceptible to predators e.x. Daphnia.
• Small size cladocerans –more cyclomorphic growth.
• Brythroptrephes –larger caudal appendages-increase handling time and decreases
predation rates by young fish.
• Copepods –thoracic legs-locomotion,Cladoceran-thoracic legs- fliter feeding.
• Rotifers-movement by propelling motions
LARVAL FORMS OF ARTHROPODS
• Crustaceans-direct and indirect development.
• Direct development( palaemon,crayfish)-adult –progressive growth.
• Indirect development-larval stages-differ from adults-metamorphosis.
• Many crustaceans undergo indirect development.
• Different larval forms-Nauplius larva,Metanauplius larva,Zoaea
larva,Mysis larva and megalopa larva.
LARVA • Simplest-commonest type-both in
freshwater and marine water.
• Body 3 distinct region-single median
eye,3 pairs of jointed
• Has locomotor organs and mandibles.
• In Brachiopods-nauplius develops
• In other crustaceans –undergo
different stages of intermediate forms.
• Well developed digestive system-
feeding on planktons.
LARVA • Later nauplius instar-process of
moulting and growth.
• Body- Cephalothorox,abdomen,pair
of caudal forks.
• Has rudimentary appendages-two
pairs of maxillae and two pairs of
• Some decapods , stomatopods ,
notostracans –life history-free
swimming metanauplius larva.
• Has single median eyes,mandible
reduced- chewing food.
• Present in almost all decapods.
• Has broad cephalothorox,curved
abdomen-assist in swimming-
provided with forked telson.
• Has helmet like carapace-two spines ,
median dorsal and a median rostrum,
two lateral spines.
• Pair of stalked movable compound
• Has rudiments of thoracic
appendages, biramous maxillipedes-
• Also known as Schizopod larva.
• Paenaeus and Lobsters-modified into
• Bears 13 pairs of appendages-
• Has 5 pairs of posterior biramous
• Abdomen-similar to adults-has 5 pairs
of biramous pleopods , pair of
uropods and telson.
• Mysis larva –beginning of the life
history of lobsters.
• In branchyuran decapods-zoaea
metamorphose into megalopa larva.
• Resembles adult crab-possess 13 pairs of
• Abdomen-6 pairs of pleopods-placed
straight in line with cephalothorax.
• Crabs-nauplius-zoaea-megalopa –adult.
• Antennule and antenna-small-sensory
• Has pair of stalked eyes.
• Cephalothorax covered by carapace.
• 4 pairs of thoracic legs –thin,long –
SIGNIFICANCE OF LARVAL FORMS
• According to biogenetic law or recapitulation theory of Haeckel-
organism-during development-repeats some extent in its evolutionary
• Successive stages of individual development-successive adult
• Nauplius –represents-ancestral forms of crustacea.
• Larvae-helpful-wide distribution of species –keep food reserves in
• It is clear that zooplankton may be good indicator of variations in the water
quality of the freshwater ecosyatem.
• It serves as a sensitive indicator of the aquatic environment which allows
ecologists to include in the system of monitoring of water status.
• A study revealed that water temperature,atmospheric temperature,and pH
were minimum during winter and maximum during summer season.
• An increase in various physio-chemical parameters has a direct effect on the
abundance of zooplankton and water quality.
1. Limnology-lake and River ecosystems,third edition.pg no:403-496 by Robert G. Wetzel.
2. Limnology book by CRC Francis and group.pg.no:272-317.
3. Modern textbook of zoology invertebrates by R.L.Kotpal .pg.no:679.
4. Limnology by Alexander J Horne,Charles R Goldman.pg.no:221-240.
5. A manual of lake morphometry by Hakanson.L
6. A treatise of Limnology by Hutchinson,G.E. Vol 1.
7. The ecology of running waters by Elster,H.J.
8. River ecology by university of California press,Berkeley.
9. Larval pictures from study and score.com.
10. Larva of crustacea by iaszoology.com.
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