Monterey Bay Aquarium Research Institute
Marine Botany

Delesseria decipiens Reproduction and Life History

Ecology | Morphology | Glossary | Acknowledgments


Delesseria, like the other members of the Division Rhodophyta, has a triphasic life history consisting of three independent life stages. Delesseria also has an isomorphic life history, meaning that it has a morphologically similar gametophyte and tetrasporophyte. Click on the picture for more information on each life stage.

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Delesseria female bladeGametophyte  The gametophyte is the stage of sexual reproduction in Delesseria, with gametes being produced from dioecious (separate sexes) haploid algae. The male gametophyte produces non-motile sperm called spermatia in reproductive structures called spermatangia that are located all over the blade of the alga. Spermatangia, which range from 5 to 10 mm in size, can often be yellow or colorless due to a lack of chloroplasts and pigments, but are often difficult to find in many red algae. Although unable to control their movement, spermatia have approximately the same specific gravity as seawater, allowing them to float for a short period in their attempt to reach a female gametophyte.
    Delesseria decipiens has an oogamous reproductive strategy, with a large, non-motile female gamete, which is housed within the female reproductive structure, the carpogonium. The carpogonium is an elongate cell with long protrusion on the end, called the trichogyne that is the site of carpogoniumspermatia attachment. The wall of the trichogyne is thought to be somewhat
sticky, perhaps with mucus, helping the spermatia to form an attachment while fertilization occurs. The carpogonium of the female gametophyte forms from a division of a pericentral cell of a fertile leaflet, forming a cell known as the supporting cell. This cell will divide further to form the carpogonial branch, on the end of which the carpogonium will form. The carpogonial branch of Delesseria always has exactly four cells. Each fertile leaflet will form only one cystocarp, although it may produce many carpogonia.

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carposporophyteCarposporophyte The carposporophyte is the only non-free living stage of the Delesseria life cycle, living embedded in the blade of the female gametophyte after fertilization. While the carposporophyte itself is diploid, it is enclosed by a pericarp, haploid tissue from the female gametophyte. The combination of the pericarp and the carposporophyte is called the cystocarp. The carposporophyte forms after fertilization when the newly formed drawing of cystocarpdiploid nucleus is transferred from the carpogonium to an auxiliary cell, which is formed only after fertilization occurs. In genus Delesseria, this transfer happens directly with no intermediate cells in between. The carposporophyte continues to divide in the auxiliary cell, forming carpospores which when released, settle and grow into the next life stage, the tetrasporophyte.

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Carpospores in the carposporophyte

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tetrasporophyte bladeTetrasporophyte The diploid tetrasporophyte represents the second asexually reproducing life stage of Delesseria and results in meiosis and the formation of haploid tetraspores. These tetraspores, when dispersed, will settle and grow into both male and female gametophytes, completing the reproduction cycle. Tetraspores are formed in the tetrasporangia, enlarged cells with dense cytoplasmic contents tetrasporesthat can be seen grouped around the midrib in D. decipiens as in the picture on the left. Tetraspores will generally form on only the last and next to last orders of branching on a particular blade. The tetrasporangia then divide to form four tetrahedrally orientated tetraspores, which look similar to the logo for a Mercedes-Benz.

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Tetraspores on the surface of a tetrasporophyte

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Delesseria Home | Taxonomy | Reproduction & Life History

Ecology | Morphology | Glossary | Acknowledgments

© Hannah Griego 2003