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Monterey Bay Aquarium Research Institute
Marine Botany

Caloplaca coralloides

A Question: What are the bumps surrounding some apothecia?

There are frequently bumps on the surface of the thallus of C. coralloides. Many of these bumps have a hole in the center. Sectioning did not definitively determine the identity of these bumps for me, because they showed only that the bumps had cortex and medulla. Here I give a hypothesis as to the identity of these bumps. If you know what these structures are or if you can help me figure them out, contact Megan Kelso at mkelso@stanford.edu or Judith Connor at MBARI.

scanning electron micrograph of apothecia of C. coralloides and zoom in of lower right hand bump
This is a scanning electron
micrograph of an apothecia

of C. coralloides and a zoomed
in look at a bump on the edge
of the apothecia.  Picture taken
by Megan Kelso with the help
of Chris Patton.


Hypothesis as to the identity of the bumps on the thallus and surrounding some apothecia:

These bumps might be apothecia in early stages of development. Maybe they will open up from the pore in the center of the bump and develop into apothecia. Sectioning the bumps did not show a developed hymenial layer, however, it is possible that it had just not developed yet. Younger looking apothecia do not have prominent bumps. Therefore, it is possible that the bumps only develop on older apothecia that have perhaps already released their spores. Pictures taken by Chris Patton and Megan Kelso of apothecia in different stages suggest that this is the identity of the bumps.

progression of images showing old apotheium with bumps around circumference, young apothecia opening up from a hole in the center, and an apothecium with what look like new small fertile patches around the circumference.

It is also possible that these bumps are simply nodules filled with medulla that form on the thalline surfaces of C. Coralloides.  However, I cannot help but think that the central hole seen in some of the bumps indicates a purpose.  It is also possible that both are true: that some of the bumps are developing apothecia and that others are simply thalline nodules.

Another thought was that the bumps could be pycnidia.  This would make sense because having the "spermatia" released right next to the fertile layer of the apothecia would help encourage successful sexual reproduction.  However, the bumps seem like they might be too large to be pycnidia.

These bumps could also be lobules, a structure for asexual reproduction that sometimes appear around the rims of apothecia.  See the section on asexual reproduction for a little moreinformation on lobules.

Overall, my best guess is that these bumps are new apothecia just beginning to develop.  

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2005 Megan Kelso

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