Lab 7Heterokonts

Heterokonts

• Common name: None• Synonyms: Stramenopiles (the

photosynthetic heterokonts are sometimes called “chromists”)

• Mode of nutrition: Autotrophic; brown chloroplasts; or saprophytic, parasitic

• Habitat: Freshwater, marine, terrestrial• Growth habit: Unicellular, filamentous,

various multicellular• Cell wall: Cellulose, silica, alginic acids

Heterokonts

• Undulipodia (“flagella”): One tinsel, usually also one whiplash

• Food storage: glycogen, laminarin, lipid• Clonal reproduction: zoospores• Sexual reproduction: Unicellular,

haploid dominant, diploid dominant, alternation of generations

• Included Phyla: Oomycota, Bacillariophyta, Phaeophyta

• Recognized by: Tinsel undulipodia

Oomycota

• General features of the heterokonts• Common name: Egg fungi, water molds• Synonyms: None (sometimes included in

the “Phycomycota” of old references; but the name properly applies to the Zygomycota)

• Mode of nutrition: Heterotrophic; saprophytic or parasitic

• Habitat: Freshwater or within host organism (which may be a terrestrial plant)

• Growth habit: Multicellular mycelium of aseptate hyphae

Oomycota

• Cell wall: Cellulose• Undulipodia (“flagella”): One

whiplash, one tinsel• Food storage: Glycogen • Clonal reproduction: Zoospores• Sexual reproduction: Diploid

dominant, oogamous• Representative genera: Phytophthora, Pythium, Saprolegnia

• Recognized by: Oogonia with 4, 8, or 16 eggs.

Saprolegnia sexual cycle

Oomycota

Bacillariophyta

• General features of the heterokonts• Common name: Diatoms• Synonyms: Chrysophyta (in part)• Mode of nutrition: Autotrophic;

brown chloroplasts• Habitat: Marine, freshwater, rarely

moist terrestrial• Growth habit: Unicellular, filamentous• Cell wall: Silica, cellulose

Bacillariophyta

• Undulipodia (“flagella”): One tinsel, on sperm cells of one Class; otherwise none.

• Food storage: Lipid• Clonal reproduction: Mitosis of unicells• Sexual reproduction: Diploid-dominant,

oogamous• Representative genera: Bacillaria, Melosira

• Recognized by: “Glassy” Cell walls with precise pores and sculpturing

Living diatoms

Bacillariophyta

Diatoms, marine

Bacillariophyta

Diatom arranged slide

Bacillariophyta

Diatom arranged slide

Bacillariophyta

Diatomaceous earth

Bacillariophyta

Melosira

Bacillariophyta

Phaeophyta

• General features of the heterokonts• Common name: Brown algae• Synonyms: None• Mode of nutrition: Autotrophic;

brown chloroplasts• Habitat: Marine• Growth habit: Multicellular;

parenchymatous, filamentous• Cell wall: Cellulose, alginic acids

Phaeophyta

• Undulipodia (“flagella”): One whiplash, one tinsel

• Food storage: Laminarin (mannitol for transport)

• Clonal reproduction: Zoospores• Sexual reproduction: Isomorphic or

heteromorphic alternation of generations, or diploid-dominant; isogamous or oogamous

• Representative genera: Ectocarpus, Fucus, Laminaria, Macrocystis, Zonaria

• Recognized by: Multicellular brown seaweeds

Ectocarpus plurilocular sporangium

Phaeophyta

Ectocarpus unilocular sporangium

Phaeophyta

Zonaria antheridia

Phaeophyta

Zonaria oogonia

Phaeophyta

Zonaria meiosporangia

Phaeophyta

Laminaria

Phaeophyta

Laminaria

Phaeophyta

Macrocystis stipe, cross section

Phaeophyta

Fucus

Phaeophyta

Fucus

Phaeophyta

seaweeds

Phaeophyta

kombu

Phaeophyta

wakame

Phaeophyta