Sexual Sporulation in the Chytridiomycota

  • During sexual sporulation ZOOSPORES are formed and released from ZOOSPORANGIA just as they are during asexual sporulation.
  • But during the sexual phase of the life cycle, zoospores from different compatible zoosporangia are attracted to one another - they come together in pairs and FUSE to form a MOTILE, BIFLAGELLATE, DIPLOID ZYGOTE.
  • The zoospores are behaving like motile gametes - for this reason we call the zoosporangia from which they originate GAMETANGIA.
  • We regard the zoospores (gametes) as being of opposite sexes, although in many species they are morphologically indistinguishable from one another.
  • Eventually, the biflagellate ZYGOTE stops swimming, loses its flagella, rounds up, develops a thick wall and becomes converted into a RESTING ZOOSPORANGIUM which is capable of surviving adverse environmental conditions.
  • When environmental conditions are once again favourable for the species, MEIOSIS occurs within the resting zoosporangium and HAPLOID ZOOSPORES are released.
  • These haploid zoospores will develop into the HAPLOID SOMATIC FORM of the species.
Diagram illustrating sexual sporulatioon in Chytridiomycota.

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