This week we have a special show. In Topic one we are joined by Jake Adams who discusses some topics about zooxanthellae, and then In topic 2, Jake interviews Dr. Dan Thornhill of The university of George Athens
As always,,A+++++++++++! Thanks Rob and Jake! So here is a basic question for everyone, Is there a way to visually tell if a coral contains zooxanthellae? Also, in the show you talked about coral bleaching and how it's caused by exposure to high lighting and high temps along with possible loss of water current. Is it the actual increase in temperature that causes the bleaching or is it the exposure to too much light? Once again, thanks for the show!
__________________ - Eddy
"Corals require an aquarium, seawater at the right temperature and salinity, waterf flow, light, food, bicarbonate/buffer, and calcium. Period. No other equipment, apparatus, magic potions, pills, voodoo, prayer, or other sacrafices are necessary." -Eric Borneman
Many thanks both - very interesting. I'v noticed corals that are bleaching or near bleaching when they are first put in the tank - then recover - so the adaptive hypothesis many explain that.
Awesome!!! This is one of the most informative, (at least for me), podcasts. I"m really surprised at the fact that Jake was able to pack so much useful info in a 30 minutes show and still make it so the information didn't go right over our heads. Awesome!!!
Unfortunately, only your intro downloaded into my itunes. Nevertheless, the show was very informative. As an experienced hobbiest, I really like the science oriented nerdy stuff. Great job!
Jake and Dan - Thanks for the time and energy invested into this terrific podcast! I finally had time to listen to it (a week late!) and I loved it!
I had a bunch of well-thought out questions (at least I thought so) while listening to the show, but I guess I'll have to listen again, because I can't remember all of them!
But, here's a try:
1. What happens to the expelled zooxanthellae from corals such as Euphyllia? Are they dead and that's why the coral is expelling them?
2. Do the zooxanthellae proliferate within the coral? Or are they proliferating while free-living and then are incorporated into the host?
3. Does anyone know what the life-span is of a single zooxanthellae?
Hey Guys. thanks for all the praise and the comments. I will try to answer all the questions, let me know if you have any more.
Is it the actual increase in temperature that causes the bleaching or is it the exposure to too much light?
Both increasing light and increasing temperature can cause a reduction of zooxanthellae concentration. IN the context of the adaptive bleaching hypothesis, it is often stressfully high water temperatures which induce expulsion of the zoox.
I'v noticed corals that are bleaching or near bleaching when they are first put in the tank - then recover - so the adaptive hypothesis many explain that.
DOnt confuse plain old regulation of zooxanthellae density for the adaptive bleaching hypothesis. Corals and symbionts are in this dance of always trying to strike a balance between the needs of the symbiont and the host. When a coral expels all its zoox, it is basically wiping the dance floor clean and starting over. ;-)
1. What happens to the expelled zooxanthellae from corals such as Euphyllia? Are they dead and that's why the coral is expelling them? When a coral does a normal expulsion of zooxanthellae, appearing as an elongated brownish mucous strand, these are mostly dead zoox but there are plenty of live ones also.
2. Do the zooxanthellae proliferate within the coral? Or are they proliferating while free-living and then are incorporated into the host?
The zooxanthellae population living inside the coral is made up of mostly cells which have divided within the host but free-living cells are always being incorporated into the host.
3. Does anyone know what the life-span is of a single zooxanthellae? I want to say that it is on the order of days to a couple weeks at most. its hard to pin down age of an organism that is constantly dividing.
Is there any validity to the idea that you can "seed" zooxanthellae? I'm not sure who originally did some of the work with blending up corals to use the zooxanthellae.
If you have a coral with a certain strain of zooxanthellae and add another genus/species of coral with the same strain can they "share"? For example if coral A is transfered from another tank and is stressed and slightly bleached (with continual polyp extension) can it borrow zooxanthellae from another coral?
Think of the symbiosis between corals and zooxanthellae as an infection, not necessarily one that causes problems like a cold but one that can be either harmless or beneficial. The coral itself is like a miniature environment for zooxanthellae. Coral A and zoox a get along well and coral b and zoox b get along well. if coral B loses all of zoox b and it there is zoox a around, it will most likely incorporate whatever zoox can live in its tissues. ALthough zoox a can live in coral b and coral b can live with zoox a, neither is as happy or prolific as when they are in symbiosis with their preffered type. As far as your sharing question goes, it is likely that there is (always) a cross infection of symbiodinium but likely in such small numbers that the prefered symbiont type is still dominant. This is assuming that the environment stays the same etc.
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