Zoid

Last updated • 6 min readFrom Wikipedia, The Free Encyclopedia

In botany, a zoid or zoïd /ˈzoʊ.ɪd/ is a reproductive cell that possesses one or more flagella, and is capable of independent movement. [1] Zoid can refer to either an asexually reproductive spore or a sexually reproductive gamete. In sexually reproductive gametes, zoids can be either male or female depending on the species. For example, some brown alga ( Phaeophyceae ) reproduce by producing multi-flagellated male and female gametes that recombine to form the diploid sporangia. [2] Zoids are primarily found in some protists, diatoms, [1] green alga, brown alga, [3] non-vascular plants, [4] and a few vascular plants (ferns, [1] cycads, [5] and Ginkgo biloba [6] ). The most common classification group that produces zoids is the heterokonts or stramenopiles. These include green alga, brown alga, oomycetes, and some protists. [7] The term is generally not used to describe motile, flagellated sperm found in animals. Zoid is also commonly confused for zooid which is a single organism that is part of a colonial animal.

Contents

Diversity of zoids

A zoid contains one or more flagella for motility. In the various species that produce zoids, there is a high level of diversity in the number of flagella produced. The heterokonts generally produce zoids with 2 flagella, [7] while the Ginkgo biloba produce zoids with tens of thousands of flagella. [6] The position of the flagella and the arrangement of the microtubules varies among species as well. The following sections will briefly outline general characteristics of the zoids found in each subset as well as provide specific examples.

Zoids in heterokonts

Heterokonts are a diverse group of eukaryotic organisms that include diatoms, green algae, and brown algae. The defining characteristic of this group is their bi-flagellate, motile sperm (zoid). [8] The two flagella are most commonly positioned apically or sub-apically depending on the type of heterokont. One flagella, the tinsel flagella, is generally longer and covered with bristles. The other flagella is typically shorter, potentially even shortened to just a basal body, and is generally smooth and whip-like. [7]

Green algae have a life cycle that includes an alternation of generations. [9] Zoids can be found in both the haploid and the diploid phases of this life cycle in certain green alga. Number of flagella is one characteristic that aids in the classification of different types of green alga. [9] Zoids are either released through pores or by lysing of the zoid-producing cells in either the gametangium or the sporangium. [10] A majority of the zoids produced within this group are either bi-flagellate or quadri-flagellate. To represent the diversity of zoids found in green alga, below is a list of genera from the family Monostromataceae which is part of the phylum Chlorophyta. [11]

  • Genus Monostroma – produces bi-flagellate gametes and quadri-flagellate zoospores
  • Genus Gayralia – produces bi-flagellate zoids in the monomorphic asexual form
  • Genus Protomonostroma – produces quadri-flagellate zoids
  • Genus Ulvopsis – produces bi-flagellate gametes, bi-flagellate asexual zoids, and quadri-flagellate zoospores
  • Genus Ulvaria – produces biflagellate gametes and quadri-flagellate zoospores

Brown algae ( Phaeophyceae ) reproduce both sexually and asexually depending on the species. However, all motile reproductive cells in the Class are flagellated and there are no free-living flagellate organisms. [1] The structure of brown algae varies depending on Family and Genus, thus zoids are produced in a variety of ways. Gametes or asexual zoospores can be produced in plurilocular zoidangia in the larger thalli of brown alga. [1] However, in smaller thalli, unilocular zoidangia produce the sexually or asexually reproductive cells. [2] Below is some vocabulary associated with brown algal zoid production: [1]

  • Plurilocular = many chambered, each chamber produces one zoid
  • Unilocular = one chamber, can produce multiple gametes in one chamber
  • Plurilocular gametangia = structure that has many chambers that produce haploid gametes
  • Plurilocular sporangia = structure that has many chambers that produce diploid spores
  • Plurilocular zoidangia = collective term for plurilocular gametangia and plurlocular sporangia
  • Plurizoids = zoids produced in a plurlocular zoidangia
  • Unilocular sporangia = can produce meiospores or asexual spores
  • Unilocular zoidangia = synonym for unilocular sporangia
  • Unizoids = zoids produced in a unilocular zoidangia

Brown alga zoids have the same two basic flagella discussed in the heterokont section. However, orientation of the flagella is unique in the Phaeophyceae . In general, the flagella are both inserted laterally. [1]

Zoids are not as common in the diatoms as in the algal families. Diatoms are generally broken into two categories, the centric diatoms and the pennate diatoms. Of these two categories, only the centric diatoms have been found to produce zoids and only the male gametes have flagella. These motile, male gametes have been found to only possess one flagellum with no signs of even a rudimentary second flagella. [12] This deviates from the standard definition of a heterokont. Because of this deviation, diatoms are often classified as "stramenopiles". [8]

Zoids in non-vascular plants and fungi

Among the non-vascular plants, specifically the Bryophytes , species that sexually reproduce will utilize zoids as their gametes. Many species of Bryophytes are primarily asexually reproducing structures that reproduce by fragmentation or cloning. [13] When the Bryophytes do reproduce sexually, the male zoids must swim from the antheridia to the archegonia. These zoids are generally bi-flagellate but this can vary species to species. [14]

Fungi are a very diverse group of organisms with very diverse life cycles. Most reproduce using spores and many do not utilize zoids for their reproduction. However, one particular class of organisms that is very closely related to fungi use a similar zoid to the heterokonts mentioned above. Oomycota or water molds are a group of potentially pathogenic fungi-like eukaryotic organisms that utilize bi-flagellate zoids as their reproductive spores. The zoids are only released in aquatic environments. These oomycetes have been responsible for disease outbreaks such as sudden oak death and the Great Famine of Ireland (early blight). [15]

Zoids in vascular plants

Zoids are found in three types of vascular plants; ferns, cycads, and Ginkgo biloba . The zoids of each of these groups are large and multi-flagellated. The mature spermatozoids of the fern Asplenium onopteris are 8 to 8.5 micrometers in length and contain 50 flagella. [16] The zoid of the cycad can be up to 300 to 500 micrometers long and can contain thousands of flagella. [5] The zoid of the ginkgo is approximately 86 micrometers long and also can contain thousands of flagella. [5] Because of the high number of flagella associated with both cycads and ginkgo, there has been some debate as to whether they are flagella or cilia. Either way, cycads and Ginkgo are rare woody plants that produce motile gametes.

Evolution

In plants, the zoid, or swimming sperm, is considered to be a trait of the "lower" land plants. In aqueous environments, the necessity for motile reproduction is obvious, but on land this adaptation loses its relevance. The zoid is most common among the non-vascular plants and the "lower" vascular plants. It is hypothesized that as the land plants evolved enclosed ovules, the necessity for a film of water and therefore motile sperm became unnecessary. [4] Motile, flagellated sperm or zoids is rare in angiosperms.

Along the same lines, the Ginkgo is a species that has no close living relative. It is believed to be most closely related to the giant seed ferns which date back to the Jurassic period. [6] This represents what would also be considered a "lower" land plant. Ginkgo were originally classified in the Taxaceae , or yew, family. When it was discovered that ginkgo had motile sperm, they were moved to their own family, Ginkgoaceae . [6]

Related Research Articles

<span class="mw-page-title-main">Chlorophyceae</span> Class of green algae

The Chlorophyceae are one of the classes of green algae, distinguished mainly on the basis of ultrastructural morphology. They are usually green due to the dominance of pigments chlorophyll a and chlorophyll b. The chloroplast may be discoid, plate-like, reticulate, cup-shaped, spiral- or ribbon-shaped in different species. Most of the members have one or more storage bodies called pyrenoids located in the chloroplast. Pyrenoids contain protein besides starch. Some green algae may store food in the form of oil droplets. They usually have a cell wall made up of an inner layer of cellulose and outer layer of pectose.

<span class="mw-page-title-main">Chlorophyta</span> Phylum of green algae

Chlorophyta is a division of green algae informally called chlorophytes.

<span class="mw-page-title-main">Flagellate</span> Group of protists with at least one whip-like appendage

A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word flagellate also describes a particular construction characteristic of many prokaryotes and eukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, several derivations of the term "flagellate" are more formally characterized.

<span class="mw-page-title-main">Gamete</span> Haploid sex cell

A gamete is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. The name gamete was introduced by the German cytologist Eduard Strasburger in 1878.

<span class="mw-page-title-main">Gametophyte</span> Haploid stage in the life cycle of plants and algae

A gametophyte is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the sexual phase in the life cycle of plants and algae. It develops sex organs that produce gametes, haploid sex cells that participate in fertilization to form a diploid zygote which has a double set of chromosomes. Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte. The sporophyte can produce haploid spores by meiosis that on germination produce a new generation of gametophytes.

<span class="mw-page-title-main">Flagellum</span> Cellular appendage functioning as locomotive or sensory organelle

A flagellum is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores (zoospores), and from a wide range of microorganisms to provide motility. Many protists with flagella are known as flagellates.

<span class="mw-page-title-main">Alternation of generations</span> Reproductive cycle of plants and algae

Alternation of generations is the predominant type of life cycle in plants and algae. In plants both phases are multicellular: the haploid sexual phase – the gametophyte – alternates with a diploid asexual phase – the sporophyte.

<span class="mw-page-title-main">Brown algae</span> Large group of multicellular algae, comprising the class Phaeophyceae

Brown algae are a large group of multicellular algae comprising the class Phaeophyceae. They include many seaweeds located in colder waters of the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and polar regions. Many brown algae, such as members of the order Fucales, commonly grow along rocky seashores. Most brown algae live in marine environments, where they play an important role both as food and as a potential habitat. For instance, Macrocystis, a kelp of the order Laminariales, may reach 60 m (200 ft) in length and forms prominent underwater kelp forests that contain a high level of biodiversity. Another example is Sargassum, which creates unique floating mats of seaweed in the tropical waters of the Sargasso Sea that serve as the habitats for many species. Some members of the class, such as kelps, are used by humans as food.

<span class="mw-page-title-main">Oomycete</span> Fungus-like eukaryotic microorganism

The Oomycetes, or Oomycota, form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms within the Stramenopiles. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the result of contact between hyphae of male antheridia and female oogonia; these spores can overwinter and are known as resting spores. Asexual reproduction involves the formation of chlamydospores and sporangia, producing motile zoospores. Oomycetes occupy both saprophytic and pathogenic lifestyles, and include some of the most notorious pathogens of plants, causing devastating diseases such as late blight of potato and sudden oak death. One oomycete, the mycoparasite Pythium oligandrum, is used for biocontrol, attacking plant pathogenic fungi. The oomycetes are also often referred to as water molds, although the water-preferring nature which led to that name is not true of most species, which are terrestrial pathogens.

<span class="mw-page-title-main">Sporophyte</span> Diploid multicellular stage in the life cycle of a plant or alga

A sporophyte is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase.

<span class="mw-page-title-main">Zoospore</span> Life cycle stage of lower organisms

A zoospore is a motile asexual spore that uses a flagellum for locomotion in aqueous or moist environments. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Certain zoospores are infectious and transmittable, such as Batrachochytrium dendrobatidis, a fungal zoospore that causes high rates of mortality in amphibians.

<span class="mw-page-title-main">Gametangium</span> Multicellular sex organs in plant life

A gametangium is a sex organ or cell in which gametes are produced that is found in many multicellular protists, algae, fungi, and the gametophytes of plants. In contrast to gametogenesis in animals, a gametangium is a haploid structure and formation of gametes does not involve meiosis.

Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes, resulting in offspring genetically different from either parent. Asexual reproduction produces new individuals without the fusion of gametes, resulting in clonal plants that are genetically identical to the parent plant and each other, unless mutations occur.

Sporogenesis is the production of spores in biology. The term is also used to refer to the process of reproduction via spores. Reproductive spores were found to be formed in eukaryotic organisms, such as plants, algae and fungi, during their normal reproductive life cycle. Dormant spores are formed, for example by certain fungi and algae, primarily in response to unfavorable growing conditions. Most eukaryotic spores are haploid and form through cell division, though some types are diploid sor dikaryons and form through cell fusion.we can also say this type of reproduction as single pollination

<i>Ginkgo</i> Genus of ancient seed plants with a single surviving species

Ginkgo is a genus of non-flowering seed plants, assigned to the gymnosperms. The scientific name is also used as the English common name. The order to which the genus belongs, Ginkgoales, first appeared in the Permian, 270 million years ago, and Ginkgo is now the only living genus within the order. The rate of evolution within the genus has been slow, and almost all its species had become extinct by the end of the Pliocene. The sole surviving species, Ginkgo biloba, is found in the wild only in China, but is cultivated around the world. The relationships between ginkgos and other groups of plants are not fully resolved.

Myriotrichia is a genus of brown algae.

<i>Scytothamnus australis</i> Species of alga

Scytothamnus australis is a brown alga species in the genus Scytothamnus found in New Zealand. It is a sulphated polysaccharide and the type species in the genus.

<i>Allomyces</i> Genus of fungi

Allomyces is a genus of fungi in the family Blastocladiaceae. It was circumscribed by British mycologist Edwin John Butler in 1911. Species in the genus have a polycentric thallus and reproduce sexually or asexually by zoospores that have a whiplash-like flagella. They are mostly isolated from soils in tropical countries, commonly in ponds, rice fields, and slow-moving rivers.

<span class="mw-page-title-main">Autospore</span>

Autospores are a type of spores that are produced by algae to enable asexual reproduction and spread. They are non-motile and non-flagellated aplanospores that are generated within a parent cell and have the same shape as the parent cell before their release. Autospores are also known as resting spores. Algae primarily use three different types of spores for asexual reproduction - autospores, zoospores, and aplanospores. Autospores occur in several groups of algae, including Eustigmatophyceae, Dinoflagellates, and green algae. One example of a colonial alga that produces autospores is Dichotomococcus. This alga generates two autospores per reproducing cell, and the autospores escape through a slit in the cell wall and remain attached to the mother cell. Some study on autospores and algae in general include looking into its use for biofuel, animal feed, food supplements, nutraceuticals, and pharmaceuticals.

<i>Phycophthorum</i> Genus of parasitic protists

Phycophthorum is a monotypic genus of protists that parasitize diatoms, containing the sole species Phycophthorum isakeiti. It was discovered in 2020 in the coastal waters of Norway, as parasites of diatoms belonging to the genus Pleurosigma.

References

  1. 1 2 3 4 5 6 7 Hoek, Christiaan van den; Mann, D. G.; Jahns, Hans Martin (1995). Algae: An introduction to phycology. UK: Cambridge University Press. ISBN   978-0-521-31687-3.
  2. 1 2 Heesch, Svenja; Peters, Akira F. (March 1999). "Scanning electron microscopy observation of host entry by two brown algae endophytic in Laminaria saccharina (Laminariales, Phaeophyceae)". Phycological Research. 47 (1): 1–5. doi:10.1111/j.1440-1835.1999.tb00277.x. ISSN   1322-0829.
  3. ↑ Lobban, Christopher S.; Wynne, Michael James (1981). The Biology of seaweeds. University of California Press. ISBN   0-520-04585-8.
  4. 1 2 Paolillo, Dominick J. (1981). "The Swimming Sperms of Land Plants". BioScience. 31 (5): 367–373. doi:10.2307/1308401. ISSN   0006-3568. JSTOR   1308401.
  5. 1 2 3 Norstog, Knut J.; Gifford, Ernest M.; Stevenson, Dennis Wm (2004). "Comparative Development of the Spermatozoids of Cycads and Ginkgo biloba". The Botanical Review. 70 (1): 5–15. doi:10.1663/0006-8101(2004)070[0005:CDOTSO]2.0.CO;2. ISSN   0006-8101.
  6. 1 2 3 4 Ogura, Y. (1967). "History of discovery of spermatozoids in Ginkgo biloba and Cycas revoluta". Phytomorphology. 17: 109–114. Retrieved 17 April 2020.
  7. 1 2 3 Andersen, Robert A. (2004). "Biology and systematics of heterokont and haptophyte algae". American Journal of Botany. 91 (10): 1508–1522. doi:10.3732/ajb.91.10.1508. PMID   21652306.
  8. 1 2 Patterson, David J. (1999). "The Diversity of Eukaryotes". The American Naturalist. 154 (S4): S96–S124. doi:10.1086/303287. ISSN   1537-5323. PMID   10527921. S2CID   4367158.
  9. 1 2 Lewis, Louise A.; McCourt, Richard M. (2004). "Green algae and the origin of land plants". American Journal of Botany. 91 (10): 1535–1556. doi:10.3732/ajb.91.10.1535. PMID   21652308.
  10. ↑ Lersten, Nels R.; Voth, Paul D. (September 1960). "Experimental Control of Zoid Discharge and Rhizoid Formation in the Green Alga Enteromorpha". Botanical Gazette. 122 (1): 33–45. doi:10.1086/336083. ISSN   0006-8071. JSTOR   2472935. S2CID   85073028.
  11. ↑ Bast, Felix; Shimada, Satoshi; Hiraoka, Masanori; Okuda, Kazuo (October 2009). "Asexual life history by biflagellate zoids in Monostroma latissimum (Ulotrichales)". Aquatic Botany. 91 (3): 213–218. doi:10.1016/j.aquabot.2009.06.006.
  12. ↑ Sato, Shinya; Beakes, Gordon; Idei, Masahiko; Nagumo, Tamotsu; Mann, David G. (26 October 2011). Lobaccaro, Jean-Marc A. (ed.). "Novel Sex Cells and Evidence for Sex Pheromones in Diatoms". PLOS ONE. 6 (10): e26923. Bibcode:2011PLoSO...626923S. doi: 10.1371/journal.pone.0026923 . ISSN   1932-6203. PMC   3202595 . PMID   22046412.
  13. ↑ Frey, Wolfgang; Kürschner, Harald (March 2011). "Asexual reproduction, habitat colonization and habitat maintenance in bryophytes". Flora - Morphology, Distribution, Functional Ecology of Plants. 206 (3): 173–184. doi:10.1016/j.flora.2010.04.020.
  14. ↑ Renzaglia, Karen S.; Bernhard, Douglas L.; Garbary, David J. (January 1999). "Developmental Ultrastructure of the Male Gamete of Selaginella". International Journal of Plant Sciences. 160 (1): 14–28. doi:10.1086/314103. ISSN   1058-5893. S2CID   85178760.
  15. ↑ Walker, Claire A.; van West, Pieter (February 2007). "Zoospore development in the oomycetes". Fungal Biology Reviews. 21 (1): 10–18. doi:10.1016/j.fbr.2007.02.001.
  16. ↑ Muccifora, S.; Gori, P. (August 2005). "Ultrastructure of mature spermatozoids in the fern Asplenium onopteris L.". Micron. 36 (6): 539–544. doi:10.1016/j.micron.2005.03.012. PMID   15975801.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.