Reproduction in Articulated Coralline Algae
The articulates reproduce both sexually as gametophytes and asexually as sporophytes and carposporophytes. All reproduction takes place inside conceptacles, small chambers on the alga's surface. Conceptacles can occur at the tip of an axial branch or on the surface of an intergenicula. All articulates have uniporate conceptacles with just one opening to the outside. Conceptacles can contain spermatangia, carpogonia, or carposporophytes.
This articulate has many bulging, uniporate conceptacles.
Fertilization of female carpogonia--egg cells--occurs when non-motile spermatia are intercepted by trichogynes. These cells have pointed tips that project into the conceptacle and intercept passing spermatia. After fusion of spermatia and carpogonia, the developing carposporophyte is transferred to a new area of the conceptacle via a gonimoblast.
A cross-section of a conceptacle bearing carpogonia.
Carposporophytes and tetrasporophytes both reproduce by releasing spores. Carposporophytes reside in the conceptacles of female gametophytes and release diploid carpospores, which develop into tetrasporophytes. Tetrasporophytes release haploid, zonate tetraspores that develop into gametophytes. A better explanation of the articulate life history can be found on the Life History page.
© 2001 Ian Ehrenreich. All rights reserved.