Lab 7 Heterokonts The heterokonts are more commonly called stramenopiles.

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.

A Saprolegnia sexual cycle Saprolegnia oogonia differ in appearance depending on whether they are pre-meiotic (they appear to contain nothing), contain eggs (which are transparent or translucent), or contain the zygotes, or “oospores”, which are dark. An antheridium shows on the top right of the bottom middle oogonium, and another on the bottom of the oogonium on the lower right. 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

U Living diatoms Bacillariophyta These diatoms were collected from Cal Poly ponds. The brown color comes from the fucoxanthin accessory pigment in the chloroplasts. The ones on the right are attached to the surface of a filamentous green alga—an organism growing on a plant is called an “epiphyte”. Bacillariophyta

A Diatoms, marine Bacillariophyta These are marine, and primarily centric. The colors are a result of mixing cells from different staining procedures. Bacillariophyta

D Diatom arranged slide These species come from a variety of habitats, and are placed together to show diversity. The art of arranging diatoms goes back to Victorian England, where artists created elaborate works to be displayed under microscopes. Bacillariophyta

D Diatom arranged slide These are close-ups of some of the cells in the arranged slide. Bacillariophyta

U Diatomaceous earth Bacillariophyta This is the diatomaceous earth sold for use in swimming pool filters. Some of the cell walls are still mostly intact, and others are crushed beyond recognition. Bacillariophyta

D Melosira Bacillariophyta The spherical cells are the zygotes, also called auxospores. 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

A Ectocarpus plurilocular sporangium There is no way of knowing whether this is a sporophyte or gametophyte, since both produce the plurilocular structures. Phaeophyta

D Ectocarpus unilocular sporangium The unilocular meiosporangia show that this is a sporophyte. Phaeophyta

A Zonaria antheridia Phaeophyta The antheridia, oogonia, and meiosporangia of Zonaria look similar because they are formed through the same developmental pathways and determined by the same genes. Phaeophyta

D Zonaria oogonia Phaeophyta

D Zonaria meiosporangia Phaeophyta

D Laminaria Phaeophyta The Laminaria in the jar is a “baby” plant—the adults are much larger, with pneumocysts and patches of meiosporangia on the blades. Phaeophyta

A Laminaria Phaeophyta The upper right shows a lower magnification view. In the large photo, it is possible to see meiospores in some of the meiosporangia. Phaeophyta

A Macrocystis stipe, cross section The conductive tissue is found in the center of the stipe. The actual trumpet cells are the large cells in the outer part of the central region. Phaeophyta

D Fucus Each white dot is the opening of a conceptacle. Sometimes paraphyses can be seen sticking out of the openings. Phaeophyta

A Fucus Phaeophyta

D seaweeds Left: A rockweed, possibly Hesperophycus or Pelvetia, from near Cambria, California. Right: Pelagophycus (elk kelp), washed up on the west side of San Clemente Island. Phaeophyta

D kombu Kombu is a Laminaria used as food in Japan. Phaeophyta

D wakame Wakame is Undaria pinnatifida, a kelp used as food in Japan. Phaeophyta