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Ecology 3
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  3. 3. INTRODUCTION  They drift,float,weekely swim in the water.  The name plankton comes from the Greek word PLANKTON which means WANDERER  DRIFTER.  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.
  4. 4. • 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 wintering populations. • Zoobenthos spend their life in sediments. • Single lake contains few species of cladocerans,copepods and rotifers.
  5. 5. • 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 the predator. • 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 around down. • 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.
  6. 6. • 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.
  7. 7. • Planktonic animals – dominated by four major groups: • (a) PROTISTS • (b) ROTIFERS • (c) CLADOCERANS • (d) COPEPODA
  8. 8. PROTOZOA ANDOTHER PROTISTS • Free living protists – ciliates, flagellates and sarcodines. • Protistan zooplankton- important microbial consumers-function- organic carbon utilization and nutrient cycling.
  9. 9. DYNAMICS OF PROTISTAN ZOOPLANKTON FLAGELLATES: • These are abundant component of zooplankton. • Feed on bacteria and fix carbon photosynthetically. • Common form include dinofalgellates. e.x . Ceratium and peridinium.
  10. 10. OTHER FLAGELLATES MALLAMONAS Volvox synura chanoflagellates
  11. 11. • The heterotrophic flagellates –two types based on size, (a) heterotrophic nanoflagellates ( below 15ʮm). (b) large heterotrophic flagellates( > 15-200ʮm). • 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. nanoflagellates Heterotrophic flagellates
  12. 12. PROTISTANFEEDING • 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 chemoreception. • 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 oxygenated epilimnion.
  13. 13. CILIATES • Major ciliate genera –freshwater protozooplankton –across spectrum of trophical lakes. • E.x. oligotrichs ( strombidium and halteria) found world wide in lakes across the trophic spectrum. • Tinintinnid ciliates –widely distributed. • Haptorid ciliates distributed abundantly. • Feed on bacteria,algae and detritus, some are carnivorous and feed on small metazoans . • Ciliates – more significant of eutrophic lakes. strombidium halteria
  14. 14. SARCODINES • In eutrophic lakes-modest average abundance • HPoorly represented in the zooplankton of freshwaters. • eliozoans –restricted vertically to epilimnion and metalimnion of stratified lakes. • In late spring sarcodines- reduces density-by –formation of fat inclusions and gas bubbles. SARCODINES
  15. 15. DISTRIBUTION • 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. strombidium) saprodinium frontonia
  16. 16. ROTIFERS • Rotifers –wide range of morphological variations . • Sessile,planktonic and non predatory – omnivorous feeding by ciliary movements. • Predatory species –Asplanchna are large and prey upon protozoa. • Most rotifers are not planktonic – sessile –inhabit litthoral substrata. ASPLANCHNA
  17. 17. FEEDING • 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 small size. • Several mechanism regulate the ingestion of suspended particles. (a) cirri of pseudotrochous (b) buccal field (c) oral canal
  18. 18. REPRODUCTION • 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.
  19. 19. ASPLANCHNA –increases when herbivorous zooplankton are more abundant. Increases contacts between males and mictic females facilitates –resting eggs. Temperature – influences –rates of biochemical reactions. Other factors affect natural population but temperature a major factor affecting birth rate,
  20. 20. CRUSTACEA • 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 regions. • 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.
  22. 22. CLADOCERANS • The suborder Cladocera includes microzooplankton –size-0.2 to 0.3mm. • Has distinct head –body –covered – cuticular carapace. • Light sensitive organs –large ,compound eye,smaller ocelli. • Has swimming appendages. • Mouth parts –large chitinized mandibles ,pair of maxillus ,mandibles and labrum.
  23. 23. FEEDING OF CLADOCERANS • Usually have five pairs of legs-attached to the ventral part of the thorax. • Legs-flattened –bear numerous hairs and long setae. • Food particles filtered by setae-between the bases of the legs –mixed with oral secretions. • 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. POLYPHEMUS LEPTODORA
  24. 24. REPRODUCTION • 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 pulex. • Photoperiod response must vary among species.
  25. 25. COPEPODS CYCLOPOID • 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 setae. • Harpactinoid copepods-litthoral- microvegetation. • Cyclopoid copepods – primarily litthoral benthic species-predominantly planktonic-in small shallow lakes. • Calanoid copepods –exclusively planktonic. CALANOID HARPACTINOID
  26. 26. FEEDING OF COPEPODS • Mouthparts of Harpactinoids-seizing and scraping particles from sedimentation and macrovegetation. • 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.
  27. 27. • Carnivorous cyclops are larger than herbivorous cyclops. • Food search by discontinuous ,irregular movements in the water / over the substratum. • Herbivorous species employ-gustatory chemoreceptor organs-food seeking – discriminate inorganic and organic particles . • Locomotion –short,jerky swimming movements,animal-propel by rapid movement of appendages. • Swimming continuous in calatinoid copepods. • Calanoid copepods do not strain particles out of the water-but –propel water by flapping of four appendages.
  29. 29. • 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.
  31. 31. 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.
  32. 32. 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 zooplankton . • High food quality algae –rich in PUFA content.
  33. 33. ZOOPLANKTONOF LENTICECOSYSTEM BIOTA OF LITTHORAL ZONE: • Lentic life- more profilic in litthoral zone-can see great concentrations of animals-distributed in recognizable communities. • 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.
  36. 36. 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.
  38. 38. BIOTA OF PROFUNDAL ZONE • 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 litthoral zone. • All organisms in this zone are heterotrophs. • Larva such as phantom larvae and pea shell clam inhabits in this zone.
  40. 40. BENTHOS OF LAKE BOTTOM • 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. MIDGE MAY FLIES TUBEWORMS
  41. 41. 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.
  43. 43. (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 firmly. • 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.
  45. 45. (2) INHABITANTS OF SPACES BETWEEN ROCKS • Mayfly and strong naids – flattened. • Include thigmotaxis and Rheotaxis. • HELLGRAMITE-large- and has spines –attach to the rocks during high current. HELLGRAMITE MAYFLY
  46. 46. (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 bottom. • Limpets like fishes-Glyptosternum , Balitora,Garra-inhabits rocks. • Loaches and carps –adhere to the rocks-Gastromyzon,Indian loach Balitora
  47. 47. • Physio-chemically –fast flowing water-cold-deep lakes. • Water temperature – low,productivity low,diversity –high. • Productivity-current-limits the amount and type of autotroph production. NOEMACHEILUS GLYPOSTERNUM GASTROMYZON BALITORA
  48. 48. 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 ecosystem. • 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 .
  50. 50. DRIFT • 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.
  52. 52. 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
  54. 54. 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
  55. 55. • 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
  56. 56. 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.
  57. 57. ADAPTIVE SIGNIFICANCE OF CYCLOMORPHOSIS • 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
  58. 58. 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.
  59. 59. NAUPLIUS LARVA • Simplest-commonest type-both in freshwater and marine water. • Body 3 distinct region-single median eye,3 pairs of jointed appendages,uniramous antennules. • Has locomotor organs and mandibles. • In Brachiopods-nauplius develops into adults. • In other crustaceans –undergo different stages of intermediate forms. • Well developed digestive system- feeding on planktons.
  60. 60. METANAUPLIUS 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 maxillipedes. • Some decapods , stomatopods , notostracans –life history-free swimming metanauplius larva. • Has single median eyes,mandible reduced- chewing food.
  61. 61. ZOAEA LARVA • 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 eyes. • Has rudiments of thoracic appendages, biramous maxillipedes- for swimming.
  62. 62. MYSIS LARVA • Also known as Schizopod larva. • Paenaeus and Lobsters-modified into mysis larva. • Bears 13 pairs of appendages- resemble mysis. • Has 5 pairs of posterior biramous thoracic appendages. • Abdomen-similar to adults-has 5 pairs of biramous pleopods , pair of uropods and telson. • Mysis larva –beginning of the life history of lobsters.
  63. 63. MEGALOPA LARVA • In branchyuran decapods-zoaea metamorphose into megalopa larva. • Resembles adult crab-possess 13 pairs of appendages. • Abdomen-6 pairs of pleopods-placed straight in line with cephalothorax. • Crabs-nauplius-zoaea-megalopa –adult. • Antennule and antenna-small-sensory function. • Has pair of stalked eyes. • Cephalothorax covered by carapace. • 4 pairs of thoracic legs –thin,long – crawling.
  64. 64. SIGNIFICANCE OF LARVAL FORMS • According to biogenetic law or recapitulation theory of Haeckel- organism-during development-repeats some extent in its evolutionary history. • Successive stages of individual development-successive adult ancestors. • Nauplius –represents-ancestral forms of crustacea. • Larvae-helpful-wide distribution of species –keep food reserves in minimum.
  65. 65. CONCLUSION • 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.
  66. 66. REFERENCES 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.