Comments on: Tunicate vs. Coral Ultimate Battle

By: Pipi

Pipi — Fri, 26 Jun 2009 06:33:12 +0000

Hi, I´m studying ascidians from a remote Island on Indonesia and there is an ascidian also overgrowing corals crazy but I have not identifyied it yet, s my question is: has Trididemnum solidum a shiny surface??
thanks in advance!

By: Miriam Goldstein

Miriam Goldstein — Sat, 17 May 2008 23:18:17 +0000

KJ – Thanks for your thoughts! I don’t think evolution in 30-40 years would be very likely without very strong selection (for example, all tunicates that didn’t reproduce x amount didn’t reproduce at all). But maybe there is strong selection that we don’t know about, or maybe there was a cryptic invasion of another population of Trididemnum that is more invasive (this happened with the salt marsh grass Phragmites on the east coast of the US).

As for being a master squatter, that has been Trididemnum’s role in the past – it does have extremely high reproduction, and preferentially settles on dead coral heads. There is certainly more dead coral than in the past, but the really big change is in Trididemnum’s ability to overgrow & kill living coral.

By: KJ

KJ — Sat, 17 May 2008 03:24:31 +0000

Interesting study.

As I read the possible reasons that may have been the root cause for the population explosion of Trididemnum. Has any work been done to explain potential changes in the Trididemnum itself. Could it have evolved become more efficent in its reproduction.

You also mentioned that you find the Trididemnum “seem to only grow on large, partically living coral”; any chance the Trididemnum have become the master squatter of the region. As soon as new land become avaiable it has so many lavae on the loose that it is able to be first on site?

Just a couple of highly unscientific thoughts.

By: Miriam Goldstein

Miriam Goldstein — Sat, 10 May 2008 13:46:41 +0000

Hee! Thanks, Gila! If you need a coral fix, the Red Sea has really some really cool & unique corals, especially gorgonians (soft corals). Spring break in Eilat?

By: Gila

Gila — Fri, 09 May 2008 12:12:55 +0000

Oh yes, the coral is much prettier. Save it!

By: Miriam Goldstein

Miriam Goldstein — Mon, 05 May 2008 13:53:34 +0000

I am filtering water for direct bacterial counts using FSH, but they won’t give me the PP:bacteria ratios. I definitely want to incubate on my next visit – but collecting will be a problem since Trididemnum seem to only grow on large, partially living coral heads. When I get back, it would be great to chat about this more over the phone. Thanks for your suggestions!

By: jebyrnes

jebyrnes — Sun, 04 May 2008 21:23:59 +0000

Hrm - here are two ideas that come out of my filter feeding work with Didemnum vexillum - 1) Examine that bacterial content in invaded v. uninvaded areas. I used cytometry, but I'd imagine there are other assays to get the relative proportion of phytoplankton v. bacteria. FYI, I have some preservation methods for water samples if you have the ability to get some glutaldehyde and liquid N2 and then transport the frozen samples home for cytometric analysis. 2) Alternately, incubate Trididemnum with water from invaded v. uninvaded areas to look at what it's feeding on - but indirectly (this is more low tech) - more bacterial consumption should mean more NH4 excretion (I can email you some citations on this). It's worked for me - Didemnum shoots out massive amounts of NH4 compared to everything else it lives with on docks, and I think that's due to more usage of bacteria. I think... I've been using the idophenol blue method for this, although Turner Designs also has a handheld ammonium sensor - similar to their in vivo chlorophyll meter that I've been using with great success.