20–5 Funguslike Protists Photo Credit: ©L.West/Photo Researchers, Inc.

Differences between Fungus and funguslike protists Funguslike protists are heterotrophs that absorb nutrients from dead or decaying organic matter. Unlike most true fungi, funguslike protists contain . They also lack the chitin cell walls of true fungi.

Slime Molds Slime molds are: At one stage of their life cycle, slime molds look just like amoebas. At other stages, they form moldlike clumps that produce spores, almost like fungi.

Slime Molds Cellular Slime Molds Most cellular slime molds live as free-living cells that are not easily distinguishable from soil amoebas. In nutrient-rich soils, these amoeboid cells reproduce sexually and produce diploid zygotes.

Life Cycle of a Cellular Slime Mold Fruiting body Emerging amoebas Solitary cell Spores Aggregated amoebas Zygote Fruiting body Cellular slime molds reproduce asexually and sexually. Migrating colony

Slime Molds When food is scarce, the cells produce spores. They emit chemicals to attract cells of the same species. Cells gather into a colony that functions like one organism. The colony moves slightly, then stops to produce a , a slender reproductive structure that produces spores. Then the spores are scattered from the fruiting body. Each spore produces one cell, starting the cycle again.

Slime Molds Acellular Slime Molds Acellular slime molds begin as amoeba-like cells. When they aggregate, their cells fuse to produce structures with many nuclei known as .

Life Cycle of an Acellular Slime Mold Fertilization Germinating Zygote Spores Mature sporangium Young sporangium Feeding plasmodium Mature plasmodium The plasmodium of an acellular slime mold is the collection of many amoeba-like organisms contained in a single cell membrane. The plasmodium will eventually produce sporangia, which in turn will undergo meiosis and produce haploid spores. Upon pairing up and fusing, these result in new diploid amoeba-like cells. 

Slime Molds Fruiting bodies, or sporangia, arise from the plasmodium. The sporangia produce haploid spores by meiosis. Zygote Mature sporangium Young sporangium Feeding plasmodium Mature plasmodium The plasmodium of an acellular slime mold is the collection of many amoeba-like organisms contained in a single cell membrane. The plasmodium will eventually produce sporangia, which in turn will undergo meiosis and produce haploid spores. Upon pairing up and fusing, these result in new diploid amoeba-like cells. 

Slime Molds Spores scatter and germinate into flagellated cells. Cells fuse to produce diploid zygotes. The plasmodium of an acellular slime mold is the collection of many amoeba-like organisms contained in a single cell membrane. The plasmodium will eventually produce sporangia, which in turn will undergo meiosis and produce haploid spores. Upon pairing up and fusing, these result in new diploid amoeba-like cells.  Germinating Spores

Water Molds , or water molds thrive on dead or decaying organic matter in water. Some water molds are plant parasites on land. Water molds produce thin filaments known as . Water molds have cell walls made of cellulose and produce motile spores, two traits that fungi do not have. Water molds reproduce both sexually and asexually.

Life Cycle of Water Molds FERTILIZATION SEXUAL REPRODUCTION MEIOSIS ASEXUAL REPRODUCTION Water molds live on decaying organic matter in water. Water molds reproduce both asexually and sexually. During asexual reproduction, flagellated spores are produced by the diploid (2N) mycelium. These spores grow into new mycelia. During sexual reproduction, a male nucleus fuses with a female nucleus.

Life Cycle of Water Moldsmolds In asexual reproduction, portions of the hyphae develop into , which are spore cases. Flagellated Spores (N) Hypha Mycelium (2N) Zoosporangium Germination and mitosis Water molds reproduce both asexually and sexually. During asexual reproduction, flagellated spores are produced by the diploid (2N) mycelium. These spores grow into new mycelia. ASEXUAL REPRODUCTION

Water Molds Each produces flagellated spores that swim in search of food. Flagellated Spores (N) Hypha Mycelium (2N) Zoosporangium Germination and mitosis Water molds reproduce both asexually and sexually. During asexual reproduction, flagellated spores are produced by the diploid (2N) mycelium. These spores grow into new mycelia. ASEXUAL REPRODUCTION

Water Molds When they find food, the spores develop into hyphae, which then grow into new organisms. Flagellated Spores (N) Hypha Mycelium (2N) Zoosporangium Germination and mitosis Water molds reproduce both asexually and sexually. During asexual reproduction, flagellated spores are produced by the diploid (2N) mycelium. These spores grow into new mycelia. ASEXUAL REPRODUCTION

Water molds Sexual reproduction occurs in specialized structures formed by the hyphae. Egg cells (N) Antheridium FERTILIZATION Zygotes (2N) MEIOSIS Oogonium Male nuclei (N) Fertilization Water molds reproduce both asexually and sexually. During sexual reproduction, a male nucleus fuses with a female nucleus. Flagellated spores (N) Mycelium (2N) Zoosporangium SEXUAL REPRODUCTION

Water molds The produces male nuclei. SEXUAL REPRODUCTION Antheridium Egg cells (N) FERTILIZATION Zygotes (2N) MEIOSIS Oogonium Male nuclei (N) Fertilization Water molds reproduce both asexually and sexually. During sexual reproduction, a male nucleus fuses with a female nucleus. Flagellated spores (N) Mycelium (2N) Zoosporangium SEXUAL REPRODUCTION Copyright Pearson Prentice Hall

Water molds The produces female nuclei. SEXUAL REPRODUCTION Oogonium Egg cells (N) Antheridium FERTILIZATION Zygotes (2N) MEIOSIS Oogonium Male nuclei (N) Fertilization Water molds reproduce both asexually and sexually. During sexual reproduction, a male nucleus fuses with a female nucleus. Flagellated spores (N) Mycelium (2N) Zoosporangium SEXUAL REPRODUCTION Copyright Pearson Prentice Hall

Water molds Fertilization occurs within the oogonium, and the spores that form develop into new organisms. Egg cells (N) Antheridium FERTILIZATION Zygotes (2N) MEIOSIS Oogonium Male nuclei (N) Fertilization Water molds reproduce both asexually and sexually. During sexual reproduction, a male nucleus fuses with a female nucleus. Flagellated spores (N) Mycelium (2N) Zoosporangium SEXUAL REPRODUCTION

Ecology of Funguslike Protists Slime molds and water molds recycle organic material. After organisms die, their tissues are broken down by slime molds, water molds, and other decomposers.

Ecology of Funguslike Protists Some funguslike protists can harm living things. Land-dwelling water molds cause a number of plant diseases, including mildews and blights. A water mold was responsible for the Great Potato Famine in the 1800s.