Monterey Bay Aquarium Research Institute
Marine Botany

Botryoglossum Reproduction

Morphology      Ecology     Life History     Taxonomy     Reproduction  

Pictures of these structures

Like all red algae, B. farlowianum has a miraculous life history which a encompasses three distinct phases. To see a pictoral representation of the life history, use the Life History link. B. farlowianum has an alteration of generations completely different from the other non-red algae. 

While the tetrasporophyte and gametophyte look almost exactly alike, except for the arrangement of sori, there is one distinct life stage. The carposporophyte stage, unique to the Rhodophyta, is one in which the offspring are produced which live, parasitic on the mother, until they reproduce themselves. 

We will begin with the haploid gametophyte stage.

Sexual reproduction in Botryoglossum is oogamous. The male gametophyte releases his non-motile spermtia into the sea. (All Rhodophyta are without flagella, even in their sperm stage.) The inability of the spermatia to propel itself is one possible reason that B. farlowianum might prefer more turbulent waters. These spermatia are thrown around by the tides until they have the good luck to stick to a female gametophyte, and fertilize her egg.  

The egg cell is called the carpogonium. This is supported by a large auxilliary cell, in a three-cell complex. There is also long, thin, hair-like cell growing up from the oocyte, called a trichogyne. This added surface area to catch onto increases the spermatia's chance of hitting upon an egg cell.

When the egg is fertilized, the carpogonium and the auxilliary cell fuse, creating one large fertilized diploid oocyte. Gonimoblast filaments shoot out from the egg cell to various parts of the plant, producing multiple zygotes. This makes the most of any fertilization event, to counter the low chances of the spermatia reaching the egg. At each gonimoblast filament end, a large, round carposporophyte is formed, which holds many diploid spores. The parasitic carposporophyte relies on the mother for all its nutrition while alive.

When the carpospores become mature, the carposporophyte becomes a large bulge. It protrudes out to one side of the thallus, and eventually bursts through, expelling the carpospores to the outside. These then well land on a suitable substrate and grow up to be a diploid tetrasporophyte. 

The tetrasporophyte plant looks just like the gametophyte plant, which is why B. farlowianum is termed an isomorphic alga. The tetrasporophytes produce tetrahedral haploid tetraspores through meiosis, which, when released, grow into haploid gametophytes.  For a pictoral version of this explanation, go to the Life History.

Morphology      Ecology     Life History     Taxonomy

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