EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 1
Eukaryotes – General
= “true nucleus”
appeared in fossil record about 1.2-1.5BY ago(2.1 - 2.5 Billion years ago)??? ck
larger cells (100-500µm vs 1-5µm):100x’s larger than prokaryotes
only one cell produces all the tasks essential for life(same as bacteria but much more efficiently since eukaryotes)
compartmentalizationnucleus, organelles
makes them much more efficient than bacteria
Origin of Eukaryotes
eukaryotic cells probably arose from two processes:
1. infolding of cell membrane to form membranebound nucleus and possibly the endoplasmic reticulum and golgi bodies
2. endosymbiosis of other prokaryotes probablyproduced mitochondria and chloroplasts and possibly the eukaryoticflagellum
evidence:
there are examples today of suchendosymbiosis
chloroplasts and mitochondria are the size ofmost bacteria
chloroplasts and mitochondria have bacterial chromosome (circular ring of DNA)
they also have bacterial RNA and bacterialenzymes
and replicate by binary fission as do bacteria
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 2
Kingdom Protista – General
~65,000 species described up to 200,000 species probable
simplest eukaryotic organisms(the other kingdoms are mainly multicellular.
very efficient cells compared to procaryotic cells
most metabolically diverse group of eucaryotes(but not more so than bacteria)
diverse group of organelles with highly developeddivision of labor
found anywhere there is water or moisture:freshwaters,marine environments,damp soil,leaf litter,snow,ice
important part of plankton:organisms that drift with currents
most unicellular, some colonial, filamentous, some (seaweeds) multicellular
multicellular forms with specializations of cells fordifferent functions:
reproductionphotosynattachmentreproductionflotationetc
autotrophs and heterotrophs
most aerobica few lack mitochondria and are anaerobic
Movement
most protists are motile
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 3
5 x’s faster(but only ~5x’s body length, vs bacteria 10-50x’s body
length at 50µm/s)eg. Paramecium 2700 µm/seg. Chlamydomonas 200µm/s
useciliaflagellaamoeboid motionglidingnonmotile
Reproduction and Life Cycles
highly varied reproduction and life cycles
true mitosis and meiosis to produce gametes
reproduce asexually and sexuallyasexually:
buddingfission & multiple fission
sexually:some by conjugation (eg. Spirogyra)some by syngamy
isogamy = similar gametesanisogamy = similar shape but
one is largeroogamy =
female is larger, nonmotilemale is smaller, motile
some produce gametes in single celled gametangium
many have both a feeding and a resistant stage intheir life cycle
some have alternation of sexual and asexualgenerations
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 4
200,000 species described
polyphyletic ie. not a natural grouping, some divide protists into 5 or 6separate kingdomsand 50 phyla
major types of organisms (Note: these are notevolutionary groupings, they are groupings of convenience, an notnecessarily the same groupings as in your text, or in other books):
1. Algae (22,000 species + fossils)mostly single celled, colonial, somemulticellular photosynthetic protists, mostwith cell wall
2. Protozoa (31,000 species + fossils)mostly single celled or colonial,heterotrophs, non photosynthetic, mostlymotile
3. Slime Molds (1,100 species)mostly complex life cyclesinvolving amoeba-like stage and fungal spore-like stage,
alternating sexual and asexual reproduction, heterotrophs
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 5
Protists - Algae
~22,000 species
diverse group of mostly photosynthetic protists
almost all are photosynthetic autotrophs=use sunlight as energy source to make organic
food
then store food as starch, leucosin, laminarin,paramylon, lipids
contain same pigment for photosynthesis as do plants chlorophyll
most also have additional “accessory” pigments
restricted to damp or wet environments:oceans, hot springsponds, atmosphere (droplets)lakes, snow,rivers, bark,soil, etc.;
most are aquatic and form phytoplankton
base of food chain in aquatic environmentsdensity only few 1000/literbut ocean area is so great that their
total productivity is:3 x’s production of all worlds grasslands and4 x’s all croplands
the larger, multicellular algae are found closer toshore usually attached to substrate in shallow water
they provide both food and shelter for many otherorganisms
a few are terrestrialfound on tree trunks and damp soil
many are symbiotic with fungi and animals
classification based on:
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 6
1. type of accessory photosynthetic pigment2. type of energy reserves3. cell wall composition
Classification
Phylum: PyrrophytaPhylum: Chrysophyta almost all single celled speciesPhylum: Euglenophyta
Phylum: Rhodophyta large multicellular speciesPhylum: Phaeophyta (no true tissues though)
Phylum: Chlorphyta mixture of unicellular, colonial andmulticellular forms
1. Fire Algae (Dinoflagellates, Pyrrophyta)
~1000 sp
unicellular
most are armoredproduce cell walls of fused interlocking cellulose plates
usually with spines
each species has a distinctive shape
2 flagella in grooves perpendicular to each other=> cause organism to spin like a top while moving
foreward
photosynthetic pigment = Chlorophyll a and orange carotenoids
food storage as starch
many symbiotic in coral animals as zooxanthellae
blooms of dinoflagellates color water red or brown= red or brown tides
some produce powerful toxins which can kill fish and other organisms that eat them
eg. 100,000’s of fish may die
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 7
eg. red tides in florida and tropical islands
eg. 1980, Maine coast – costs $7M losses
shellfish often not hurt by toxins but can accumulate and concentrate them
may make them dangerous to humans
some are bioluminescent= “burning of the sea” at night
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 8
2. Diatoms (glass algae, Chrysophyta, golden-brownalgae)
~10,000 sp
most abundant group of algae
major base of aquatic food chains (fw and marine)=phytoplankton
single celled (unicellular)
very distinctive group
cell walls:
no cellulose, has protein = pectin
also contains silica
radial symmetry
CW in two parts (petri dish)
CW of large numbers of intricately shaped pits,pores and passageways
pigments: chlorophyull a and fucoxanthin
food storage as leucosin
no cilia or flagella
some have gliding movement = slime trail
Reproduction:
asexual:shell halves separate andnew smaller shell is secreted to fit into old shell
half
sexual:male and female cells unite to formzygote which secretes new shell
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 9
Economic Impact
all oil reserves were formed mainly by diatom deposits
source of diatomaceous earth= chalky rock composed of diatom shells (fossil)
(white cliffs of Dover)
silica in shells make them useful for:filterscementplasterpaperpaintpesticidesabrasives
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 10
3. Euglenoids
~800 sp
small group
unicellular,
motile by flagellum
mostly freshwater
mainly in eutrophic ponds and pools(=lots of nutrients and organic material, eg farm ponds)
most unusual feature is lack of cell wall
flexible pellicle covering instead
food stored as paramylon (a polysaccharide found nowhere else inliving world)
has stigma = photoreceptor => attracted to light
has chloroplasts but can survive without them as well(lives in dark like protozoan)
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 11
4. Green Algae
~7000 sp
most diverse group of algae in sizes and shapes
most are freshwater
some terrestrial
found in a wide variety of habitats includingsnowtree trunkssoil
diverse body forms,
some form lichens with fungi;
mostly unicellular and colonial,
some coenocytic siphonous,
filaments or sheets;
probably gave rise to plant kingdom;
motile by flagella,
very similar cell structure to plants:pigments mainly chlorophyll a and bfood stored as starchcell wall mainly of cellulose
plants probably evolved from a green alga
some with light sensitive “eyespot” = stigma
some multicellular filamentous forms andsmall seaweeds (eg sea lettuce)
some chlamydomonas-like cells live in colonies of4,8,16 or 32
they are connected by cytoplasmic strands
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 12
most spectacular colonial form is Volvox:500-60,000 cellsfront and back endsvegetative and reproductive cellsproduce daughter colonies within adult sphere
tendency toward multicellularity
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5. Brown Algae (phaeophyta)
~1500 sp
all multicellular seaweeds,
almost all marine
usually inhabit cooler, rocky shores, intertidal areas
most large seaweeds are in this group
giant kelp can grow 300 ft long
kelp beds can be so dense they are essentiallyjungles
provide food and home for numerous sea creatures
cell wall of cellulose
complex specializations of cells into structures ofspecific functions:
bladestipe (stalk)floatsholdfast – attaches to solid surface
rapid growth rate: can renew tissues 1-5 x’s/yr
pigments: chlorophyll a and brown fucoxanthin gives them a dark brown or olive green appearance
stores foods as laminarin and lipids
life cycle usually involvesalternation of generations:
seaweed produces sporangiumsporangium produces male or female sporesspores grow into male or female sporophytessporophyte produces egg or spermzygote produces seaweed again
Sargassum
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 14
=gulfweed, rockweed, seaholly
sargassum refers to ‘grapelike’ appearance of gas bladders
only seaweed that is not attached to a substrate it’s planktonic
sargasso sea~2/3rd ‘s area of cont UStrapped in ring of currents in atlantic
sargassum can live for many yearsreproduces mainly by fragmentationwhen it becomes too encrusted it slowy sinks
to bottomsome weed is blown to gulf shores by winds
and currents
entire ecosystem of different organisms highlyadapted to it: crabs, shrimp, pipefish, “furry white” bryozoa,sargassum fish “Histrio histrio”
lots of camoflage
Economic Impacts:
used as food especially in SE Asian countries;
Kelp
kelp forests in the pacific provide such products as Kombu, Barech and Seche.
Alginates
Alginates are derived from various species of brown algae including Macrocystis, Laminaria and Fucus.About half of the ice cream in the US contains alginates.
It is used to produce a smooth consistency and eliminate ice crystals in icecreams. It is also used in somecheeses and frostings.
alginates used to make a wound dressing that speeds healing of leg ulcers
Fertilizers:seaweeds contain iodine, K, N, Pequivalent to manure
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 15
6. Red Algae (rhodophyta)
~4000 sp
especially abundant in warm tropical waters,(found in deeper waters than green algae)
mostly marine
body of filaments or sheets
most are multicellular seaweedssome differentiation of cells into:
stalks, floats, blades in some speciesoften attached to substrate by holdfast
cell wall of cellulose but often has othercarbohydrates (eg. agar)
some can deposit calcium carbonate in their cellwalls
= coralline algae important component of coral reefs
pigments: include chorophyll a and red pigment = phycobilin (more effective at capturing light in deeper water))
food stored as starch
Economic Impacts:
thick starchy cell walls yield commercial quantities of agar Agar
Agar is extracted from several red seaweeds including Gelidium sp. and Gracilarid sp. It is used in themanufacture of processed cheese, mayonnaise, puddings, jellies, baking products and canned goods.
agar: capsules for pillscosmetic baseculture mediajellies, puddings and dessertsmayonnaisecanned goodssome cheeses
Nori
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 16
The red seaweed, Porphyra, is cultivated in Japan. There are several species that are roasted andsometimes soaked in sugar and soy sauce for soup flavorings, wrapped rice crackers and to make otheroriental dishes
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 17
Protists - Protozoa
~31,000 living species; ~10,000 of these are parasitic
animal like protists
share several animal-like traits:lack cell wall,most are motileheterotrophic nutrition,
animals probably evolved from some kind ofprotozoan
most are single cell (=solitary)
a few are colonial
most are microscopic (3-300µm)
have been found in all aquatic environments
form important part of plankton (=zooplankton)
some found in terrestrial habitats where moisture isabundant:
sandsoildecaying organic matter
some are parasitic or symbiotic in animals
most are motile byciliaflagellaamoeboid motion (form pseudopodia)
(found in amoebas and some flagellates)
can also use cilia or flagella to create water currentsfor feeding
most have optimum temperature range of36 – 40 º C (=96.8 – 104º F)
heterotrophs = feed by:
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 18
1. absorbing dissolved organic nutrientsthrough cell membrane
2. ingest solid particlesthrough a mouth-like opening (=cytostome)
eat bacteria, algae, other protozoa, etc
some are saprophytic(=eat decaying organic matter)
3. ingesting solids or liquidsthrough cell membrane (phagocytosis &
pinocytosis)
food becomes enclosed in vacuole which travelsthrough cytoplasm
digestive enzymes are injected into the vacuoleand digest the food
undigested material is expelled by a reverseprocess (exocytosis) or through an “anal pore”
Life Cycles
a. most protozoa exist in a single form which feeds andreproduces
b. some alternate between two stages in their lifecycle:
troph = active vegetative feeding form
cyst = more resistant stage,low metabolic ratemay have wall of cellulose, silica or a
chitin-like substance
c. some parasitic forms have several different stagesin more than one host
Reproduction
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 19
reproduce both asexually and sexually:asexual: main form of reproduction
fission = divide in equal halves(not same as bacterial fission)eucaryotic fission involves mitosis
some split longitudinally (flagellages)
some split transversely (ciliates)
budding = unequal fission
multiple fission = >2 daughter cells(some flagellates, sarcodines, most sporozoans)
sexual: involves some exchange of genes
conjugation = exchange of a few genes(ciliates only)
syngamy = fusion of gametes
Classification
protozoa are classified according to presence and typeof motility:
amoeboid motionflagellacilianonmotile
Phylum: Sarcomastigophora
Subphylum: Mastigophora – 1 or more flagella
Subphylum: Sarcodina – amoeboid pseudopodia
Phylum: Ciliophora – ciliates
Phylum: Apicomplexa: - no cilia or flagella non motile all are parasitic
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 20
1. Amoebas
amoeba = “to change form”
Include protozoa that move by pseudopodia(=false feet)
related to changes in consistency of the cytoplasm:ectoplasm = gelendoplasm = liquid
organism can alternate between solid gel-like andliquid cytoplasm to produce pseudopodia;
simplest protozoans relatively few organelles
may be naked or enclosed within shell or case:
only phylum of protozoan with extensive fossilrecord
the shell may be composed of materials secretedby cytoplasm or
foreign material embedded in cement likesecretion
two most important shelled forms:radiolaria secrete a silica shell (SiO2), andforaminiferans produce calcium carbonate shells (CaCO3)
reproduce mostly asexually
a few reproduce sexually
Human Impacts:
Human pathogens include:
1. Entamoeba hystolytica
amoebic dysenteryesp tropics and areas of poor sanitation
(5% infection in temperate areas)humans only reservoirspread by fecal/oral route
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invade intestinal mucosafeed on RBC’s90% are asymptomaticcan cause ulcerations and profuse bleeding in acute casescysts passed in fecesmay spread to liver, lungs, brain, etc
2. Naegleria fowleri
causes always-fatal primary amoebic meningoencephalitis orPAM
mature adults seem to be immuneprefers warm waters with a high iron contentmay prefer areas where other organisms have been wiped
out by natural or man made disasters (eg Mt. St.Helens)
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2. Flagellates
cell membrane surrounded by pellicle
move using one or a few long flagella
some have “sail-like” undulating membrane(also used for food gathering and locomotion)
most are symbionts as either mutualists orcommensals
eg. such as those in the gut of termites
some are pathogenseg. such as Giardia, Trypanosoma,
most flagellates are not closely related to other protozoans probably include several phyla
Human Impacts:
Human Pathogens:
1. Trichomonas
several species (esp. T. vaginalis)human urogenital tract:
like acidity of female tractone of most common infections in US
(2.5 M inf/yr: 3-15% US infected)no cyst form requires personal contact
occasionally spread in communal baths and mother tochild
both male and female infectedesp in promiscuous young women who are already
infected with other STD’s~50% are asymptomatic carrierssymptoms: women -frothy, smelly green
discharge; painful urination
[T. tenax – 5-10% oral infectionsesp with poor oral hygeine]
2. Giardia
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 23
pear shapeddiarrheahumans are final (definitive) hostno intermediate hostsworldwide distributioninfect upper small intestineno invasive ability – saprophyticin large #’s can cause chronic diarrhea,
dehydrationcysts shed in fecesfecal/oral transmissionepidemics associated with contaminated water
3. Trypanosoma (African Sleeping Sickness)
esp in Africa20,000 cases/yr (1988)two hosts:
tsetse fly = definitive hosthumans and other animals
intermediate hostsmoves into blood and lymphatic systemaffects CNS: personality changes,
behavior changes, headaches, apathy, NM disorders,sleepiness, emaciation
may result in death from coma,malnutrition, secondary infections
4. Chagas disease (T. cruzi)
Mexico, Central America, So. Americaonly a few cases in extreme SW US40-50% of population in So. Americareservoirs: rodents, possums, armadillosvector: “kissing bug”: bites lips, defecates while
feeding and may be rubbed into wound by scratchingbite
most dangerous to childrensymptoms somewhat similar to sleeping sicknessmay also affects many organs; eg. brain, heart,
intestines
5. Leishmania
zoonosisespecially in equatorial areas
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 24
transmitted by phlebotomid (sandfly) vectorinjected directly into human hostreproduces inside WBC’stwo forms:
cutaneous form:begins with skin ulcer at site of infectionmay recur after healingmay spread to nose, lips, palate, throatdeath from bacterial infection
systemic form:produces high intermittant feverenlarged spleen, liver and lymph glands75-90% death rate
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3. Ciliates
The largest most diverse group of single celled'protozoan' protists;
genetically as diverse as entire animal kingdom
mostly are freeliving
in a wide variety of habitats.
motile by means of cilia= 1000’s oarlike projections
produce coordinated movements
fastest of the protozoans
a few are nonmotile: attached to substrate by stalk
use cilia for feeding, not movement
Wide variation in #’s and kinds of organelles:
more than one nucleus,some macronucleus => vegetative chores
micronuclei (up to 80) => sexual reproduction
“mouth” and throatlike area,most feed on microorganisms – have mouthlike cytostome;opens into a throat; food vacuole forms at end of throat
contractile vacuoles, etcsome fw forms use to remove incomming water
trichocysts
some ciliates can steal chloroplasts from the algaethey eat
Reproduction:asexual: binary fissionsexual: conjugation: portion of micronuclei are
exchanged between + and – forms
Human Impacts:
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 26
Human Pathogens:
1. Balantidium coli
ony ciliate that is a human parasitezoonosis: esp in sheep, cattle, pigs, horsesrare in USesp in hosts with weakened defensescan be asymptomaticcauses erosion of intestinal liningproduces nausea, vomiting, bloody diarrhea
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 27
4. Apicomplexa (Sporozoa)
All members of this group are nonmotile
are endoparasites
most have fairly complex life cyclessame species exists in lots of different formsalternating between forms that reproduce sexually
and those that reproduce asexually.
Human Impacts:
Human parasites include:
1. Plasmodium (malaria)single most important disease hazard for
people traveling to foreign lands(esp. Asia, Africa, Latin America)
worldwide infects 270M and kills 2M/yrin some parts of world is chronic
relatively rare in US (usually travelers)4 species, all can infect humansrequires two hosts to complete life cycle:
sexual reprodoccurs in Anopheles mosquitoreproduces in salivary glands
asexual reproductionoccurs in humansconcentrates in liver
symptoms: cyclic chills/fever, headache every 3-4 daysif not treat may be self limiting but may be reservoir for up
to 3 yearscan produce irreversible damage to liver, spleen, kidneys
and brainmost effective prevention is elimination of mosquitoWHO has been trying to eliminate it but with little successmosquitoes have developed resistance to insecticideshas developed antibiotic resistanceexperimental vaccines being testedsome living in endemic areas have developed
genetic resistance to disease (sickle cell)
2. Toxoplasma
zoonosis
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 28
cats are main reservoir and definitive hosthumans contract by contaminated soil, cat feces (litter box),
infected meatgenerally no human-human transferasymptomatic in adultsif pregnant can cross placenta and cause retardation,
blindness and convulsions in embryo or newborn
3. Pneumocystis
common secondary infection of AIDS victims
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 29
Protists:Slime Molds & Water Molds
~1100 species
Superficially resemble fungi;nonphotosyntheticbody of threadlike filaments = hyphae fruiting body a sporangium producing spores
fungus like, but: produce flagellate reproductive cells and
some have cell wall of cellulose,others with cell walls of chitin
feeding stage is amoeba-like motile
common in cool, moist shady placeseg. crevasses of rotting wood
most easily found in summer and early fall
fruiting body is the most likely to be seen very small (~1-2mm) goblets, globes, plumules with or without a stalk often colored yellow, orange, red
for most of a slime molds life it exists as a thin, free-living mass of protoplasm up to several inches across that moves aroundand engulfs bacteria and organic matter
it is thick and slimy to the touch
after its feeding period it moves out of its normalhabitat and goes to a drier, more exposed location to produce a fruitingbody
fruiting bodies can also be produced by absence of food, changesin moisture, pH, temperature
once begun, it cannot be reversed
some can produced a hardened resistant sclerotiumto survive adverse conditions
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fossils of this group has the distinction of being the firsttrue fossil that actually shows an organism caught in the act of sexualreproduction (65MY)
Classification:
three major Phyla:1. plasmodial slime molds (Myxomycota)2. cellular slime molds (Acrasiomycota)3. water molds (Oomycota)
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1. Plasmodial Slime Molds
~700 species
life cycle has two major stages:feeding stage (nonreproductive)sporangia (reproductive)
feeding stage = plasmodiumwall-less amoeba-like masslarge single cellthin streaming masses of cytoplasmcreep along in amoeboid fashioncan cover an area of several square yards (to 30 g = ~ 1oz)growth continues as long as there is adequate food and
moisturewhen in short supply they migrate away from feeding area
(often seen crossing roads, lawns, climbing trees, etc)some species form extensive growths on lawns, croplands
do little, if any, damage
eg. Fuligo septica plasmodium (shades of war of the worlds)
1973 found in Dallas suburb & reported in paper appeared on lawns as bright yellow masses spread over large areas described in paper as a “pulsating yellow blob” blobs broke apart when sprayed with hose but pieces continued to crawl around caused local panic: must be indestructible aliens from space or mutant bacteria that might take over the earth excitement soon dissipated once identified biologists “saved the world!”
when food supply dwindles reproduction is initiatedplasmodium divides into numerous moundseach mound forms cells surrounded by cell wallsproduce multicellular fruiting body = sporangiumhas cell walls on cellsvery similar to those of fungiproduces very resistant reproductive spores
spores are haploid cells
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flagellated (=swarm cells)or amoeba like (=myxamoeba)
this group is probably more closely related to amoebas than to fungi
Economic Importance:
Veracruz Mexico:some are collected, fried and eaten by indigenous
peoplescalled “cacade luna”
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2. Cellular Slime Molds
~70 species
superficially resemble the plasmodial slime molds
also closely resemble amoeba
life cycle also involvesfeeding stagereproductive stage
feeding stage consist of individual amoeba-like cellswhen food or moisture runs out cells aggregateform a single multicellular organism = pseudoplasmodium
(=slug)the slug develops a stalked structure (the fruiting body) which
produces spores
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3. Water Molds
~580 species
mainly soil and water borne organisms
once classified with fungi: have hyphae and myceliumbut differ significantly in fundamental structures and biochemistry
most commonly seen as the fuzzy filaments on deadaquarium fish
hyphae are coenocytic (= 1 giant multinucleate, filamentous cell)
has both asexual and sexual reproductive stages:asexual: zoosporangium producing zoosporessexual: antheridium and oogonium producing oospores
Economic Impacts:
some are serious plant pathogenseg. downy mildew
affects grapesintroduced into France in late 1800’salmost destroyed the wine industryproblem was accidentally solved using copper
sulfate and lime
eg. Phytophthora infestansCause of Irish Potato Famine (1845-7)
in Irelandvirtually the entire Irish potato crop was wiped
out in one week> 1 million deaths from starvationbegan large scale emmigration of Irish to US
within a decade the population of Irelanddropped 50%: 8M -> 4M
eg. other Phytophthora specieshave caused widespread destruction of many
crops throughout the world:pineapplestomatoes,rubber,onionsstrawberries
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 35
applessoybeanstobaccocitrus