MYXOMYCETESANDZYGOMYCETES

MarilenM.ParungaoBiology112Laboratory

MYXOMYCETES:WHYSTUDYTHEMHERE?

• Membersofthisdivisionarecommonlyreferredtoasslimemolds.

•  ClassifiedasPro8sts:sincetheyformamoeboidcells

•  RegardedasFungi:becausetheyproducesporesthatareborneinsporangia

MYXOMYCETES

SomeImportantTerms

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PLASMODIUM

•  Anakedmul8nucleatemassofprotoplasmthatmovesandfeedsinanamoeboidfashion

•  FormedaDernumerousmito8cdivisionofthezygote

MYXAMOEBA

•  Anamoeboidcellreleasedbythesporeupongermina8on

•  Maycon8nuetoproliferateforanindefiniteperiodof8meifthereisavailablenutrientandtheenvironmentremainsfavorable

•  2func8ons:ingestfoodorfunc8onasgametesduringduringreproduc8on

SWARMCELLS

•  Whenfreewaterisavailable,myxamoebaecanbecomeflagellatedandswimthroughthewater

•  Duringcondi8onsunfavorableformyxamoebaegrowth,thecellsmayroundupandformtheresistantmicrocyststage

SCLEROTIA

•  Ahardres8ngbodyresistanttounfavorablecondi8ons

•  Whencondi8onsbecomeunfavorable,aplasmodiumcanbecomedormantformingaresistantstages

•  Actuallycomposedofsmallerunitscalledmacrocysts

PHYSARUMTYPICALLIFECYCLE

FRUTINGBODIES

•  Frui8ngbodiesmayeitherbecarryingsporesexternallyorinternally

•  Exospores:ExampleCera%omyxa– Columnar,branchedstructuresbearsthesporesexternally

FRUITINGSTRUCTURETYPE1:PLASMODIOCARP

•  Anelongated,curvedorbranched,vein‐likefrui8ngstructure

•  Example:Hemitrichiaserpula– Thesporesandcapilli8umofthissporangiumtyperetainstheshapeoftheplasmodialstage

FRUTINGSTRUCTURETYPE2:SPORANGIUM

•  Sac‐likestructure

•  Example:PhysarumandDydmium

•  thefragile,outerlayerofthesporangiumistheperidiumwhichmaybepersistentordegeneratebythe8methesporangiumisreadytodisperseitsspores

OTHERGENERAFORMINGSPORANGIUM

ArcyriaandStemoni@s

FRUITINGSTRUCTURETYPE3:AETHALIUM

•  aethaliumresemblesasessilesporangiumbutismuchlargerandgenerallycushioned– Believedtobefusedsporangium

•  Example:– Lycogala=pseudocapilli8umwithoutanydis8nc8veornamenta8onandspores

– Fuligo=producesthelargestknownaethalium

VARIATIONSINCAPILLITIUMMORPHOLOGY

Example:Trichiafavoginea,capilli8umornamentedwithannularrings

Example:Hemitrichiaserpula,capilli8umunbranched.Composedofstrandsofelaters.Elatersornamentedwithdoublespirals,eachcomingfromopposite direc8ons

Example:Lycogalaepidendrum,Capilli8um(actuallypseudocapilli8um)withoutanydis8nc8veornamenta8onandspores

ACRASIN•  Chemotac8cchemicalsthatactaspheromonesinaggrega8onofamoebaeincellularslimemolds

•  Oneoftheearliestiden8fiedacrasins:cyclicAMPorcAMP– Dictyosteliumdiscoideum– exhibitsacomplexswirling‐pulsa8ngspiralpaUernwhenformingapseudoplasmodium

ZYGOMYCOTA

“thesaprobes,faculta@veparasitesandaircontaminants”

IMPORTANTTERMS

•  ZYGOSPORE– Ares8ngsporethatresultsfromthefusionof2gametangia

•  ZYGOSPORANGIUM– Asporangiumcontainingazygospore

•  ZYGOPHORE– Aspecialhyphacapableofdevelopingintoaprogametangium

DIMORPHICGROWTH•  Producingtwomorphologically‐dis8ncttypesofzoospores(yeastformormycelialform)

•  Usuallytheyeasttypeoccursinternallyandthemycelialtypeoccursexternally(withexcep8ons)

MUCOR

MucorversusRhizopus

PHYCOMYCES

ABSIDIA

PILOBOLUS

•  Uniquesporedispersalmechanism

•  “shot‐gunfungi”

SPOREDISPERSAL•  Ini8alresulttophototrophicresponseofthesporangiophoreandlateritselonga8on

•  Steps:– Sporangiophorebendstowardsthelight(sporangialvesicleactaslens)

– Subsporangialvesiclehashighturgorpressure,uponrupturewillejectthesporangiumtowardsthesourceoflight

hUp://www.chlorofilms.org/index.php/crpVideo/display/videoid/51

DIFFERENCESBETWEENORDERS•  ORDERMUCORALES

–  Theyhaveawelldevelopedmyceliathatisgenerallyaseptate.Wheneverseptawillbepresent,theylacksporeswithspecializedplugs

•  ORDERDIMARGARITALES–  TheyaremonotypicunliketheMucorales,theyarehaustorial

mycoparasites

•  ORDERKICKXELLALES–  Producessingle‐sporesmerosporangia,usuallyfromstructurescalled

pseudophialidesthatareborneonspecializedseptateoraseptatefer8lebranchescalledsporocladia

•  ORDERENDOGONALES–  Theirsporocarpscontainonlyzygosporesandsporangiaareunknown

DIFFERENCESBETWEENORDERS•  ORDERGLOMALES

– TheyarereferredtoasVAMfungiorvesicular‐arbuscularmycorrizaeorendomycorrhizae.Thisgroupmaybefoundin70%ofallplantfamilies

•  ORDERENTOMOPHTHORALES– Thisgroupincludestheinsectpathogens

•  ORDERZOOPAGALES– TheZoopagalescomprisesthefungalgroupwithinterac8onsthatinvolveavarietyofsmallanimalsandotherfungi,althoughmycoparasi8cspeciesmayalsobeobserved

FORMATIONOFZYGOSPORE

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