Monterey Bay Aquarium Research Institute
Marine Botany

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Nongeniculate coralline

Life History

Diagram   Steps   Variations

Like most red algae, the coralline life history is very complex. It has three stages in its life history: sporophyte, gametophyte and carposporophyte.  Corallines have conceptacles with contain the reproductive structures of the cell and are often very hard. The life stages are very difficult to tell apart (isomorphic) without cross sectioning the alga. However, for some like Melobesia the life stages are heteromorphic, the sporophyte is multiporate and the gametophyte is uniporate. (see life cycle photo page)

Steps of the life cycle (click on cartoon conceptacle to see actual picture):

 

life history diagram of coralline algae

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  1. The sporophyte (2N) under goes meiosis.

  2. The tetrasporangia of the sporophyte (2N)  produces zonate tetraspores (N) and releases them.

  3. The spores (N) become either male or female gametophytes (N).

  4. The male gametophyte (N) houses the spermatangia which makes spermatia (N) (sperm without flagella).

  5. The female gametophte (N) makes eggs each with a trichogyne. The trichogyne is the terminal end of the egg and is used to catch the spermatia.

  6. The spermatia (N) travels to the egg (N) and fertilizes it.

  7. The zygote divides by mitosis and makes the carposporophyte (2N). The multicellular carposporophyte (2N) lives like a parasite in the female gametophyte conceptacle (N). The carposporophyte (2N) makes and releases the carpospores (2N).

  8. The carpospores (2N) are released and each make a sporophyte (2N).

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Now, there are many variations off this basic reproduction pathway. It is not known how often the variations take place and exactly which species have them. Corallines can make bispores (2 spores) or even trispores (3 spores) instead of the normal tetraspores (4 spores). The number of nuclei per spore can vary depending on species (this is not known for all species). Corallines can undergo apomictic cycles (asexual reproduction) where  diploid spores go through mitosis and become sporophytes again. In addition, pieces of the gametophyte and sporophyte may break off and propagate growing into a new thallus.

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© 2001 Melissa Roth