Coral reefer
Past President
Maybe you could learn how to spell zooxanthellae!
Zooxanthellae
- Thread starter Bruce Spiegelman
- Start date
I use the Asian spelling thank you very much. Besides I'm a writer -- I hire an editor for things like that at the appropriate time.
Btw -- is there anyway to sticky Gabe's response in a forum made just for posts of this nature? "From the BAR Science Base" A lot of time's we ask the same questions over-and-over and it would be nice to have a central database to go look at. Stickied posts could be voted on the the board as to relevance before showing up there, etc. We run into this about UV often, and a few other items.
gaberosenfield
Guest
Whenever the SARS-COV-2 pandemic is under control, I'd enjoy a discussion with you all at a meeting! I'm happy to share any knowledge I have and it's always gratifying to find that someone is interested in my and my colleagues' work 
Plus, through Stanford I have access to almost all online scientific literature, so if I don't know the answer to a question I may be able to find one for you
And I'd be open to a video conference as well. Just let me know!
Plus, through Stanford I have access to almost all online scientific literature, so if I don't know the answer to a question I may be able to find one for you
And I'd be open to a video conference as well. Just let me know!
gaberosenfield
Guest
Tridacna clams, and many types of coral, produce larvae that do not contain algal symbionts. The larvae or post-settlement adult phases of these animals must obtain their symbionts from the environment. This mode of symbiont acquisition is called horizontal transmission. Some coral species produce larvae that already contain symbiotic algae from their parents, a mode of symbiont acquisition termed vertical transmission.
For marine invertebrates that require Symbiodinaceae algae as adults and must acquire them horizontally, @Flagg37 is correct that they require compatible algae in the environment, at least around the time they metamorphose from a planktonic larvae into a sessile form. This should never be a problem in an established aquarium (or in the wild) because Symbiodinaceae algae are pretty common on sand, rock, and other benthic environments exposed to light. But extra algae may have to be added to the system if you're trying to breed Tridacna clams in a more "sterile" environment. Again, I want to stress that we should all rely on empirical evidence to decide whether adding extra Symbiodinaceae helps in any particular circumstance. Also, although adding extra Symbiodinaceae may not be required for juvenile clams or corals to acquire algal symbionts, filter feeding species like Tridacna clams probably still benefit from adding extra microalgae to the water simply as an added food source.
As a side note, it's worth remembering that although both Tridacna clams and photosynthetic cnidarians rely on Symbiodinaceae algae, these symbioses evolved more-or-less independently. Corals and anemones contain the algae inside their gastrodermal cells (referred to in the figure below as "endoderm", which form a tissue that lines cnidarians' gastric cavities):
Within cnidarian endodermal/gastrodermal cells, the algae are encased inside membrane-bound structures in called "symbiosomes". You can see a cross section of part of a single symbiosome with an algal cell inside in the electron micrograph below. The top of the image is inside a coral gastrodermal cell (the host cytoplasm), and arrows point to the layers of membrane that encase the algal cell:
This intracellular endosymbiotic arrangement is similar to the way mitochondria live inside our own cells (and inside coral cells), albeit mitochondria are permanent residents of our cells and cnidarians can lose their algae.
In contrast, Tridacna clams house their Symbiodinaceae algae inside their bodies but not inside their cells (extracellular endosymbiosis). These clams have a separate circulatory system of tubes throughout their mantles in which they house their algae. This circulatory system has an opening in their stomach, so the clams can infect their algal tube system with Symbiodinaceae algae they filter from the water into their gut. See the illustration below for a side and top down illustration of these tubes (labeled PZT, SZT, and TZT, stomach labeled S) in a Tridacna clam:
Within these "zooxanthellal tubes", the Symbiodinaceae algae are free (not encased in a symbiosome).
NanoCrazed
Guest
@Bruce Spiegelman late to the party as usual... you figured being sheltered in I would have more time to cruise the forums... but nope. sadly.
But yeah -- I lover the stuff. I use it religiously now as part of my tank regiment, particularly across all my nem tanks.
I'm actually curious about GFP "invading" other corals; do you remember the name of the speaker?
Coral reefer
Past President
Unfortunately no. It was in like 2010 or 2011.
gaberosenfield
Guest
Technically, GFP (Green Fluorescent Protein) is a protein naturally produced by a species of jellyfish (Aequorea victoria), but researchers now use the name GFP to refer to a large number of structurally similar naturally occurring and artificially modified fluorescent proteins. Corals produce some proteins like this, as well as other types of fluorescent and non-fluorescent protein and non-protein pigments.
To my knowledge, this has nothing to do with "zooxanthellae", as dinoflagellates do not naturally produce GFP.
The GF protein itself can't really "invade" other corals, as it cannot make copies of itself and is no more alive or infectious than any other non-prion protein (e.g. collagen).
That said, and I want to emphasize this is pure speculation, it is theoretically possible that a gene encoding GFP could be transferred from one type of coral to another through one of several processes grouped under the term "horizontal gene transfer". The most common way genes can be transferred between two species or strains of organisms is by way of a virus that incorporates itself into the genome of its host (e.g. HIV, although many other less virulent viruses also integrate into the genomes of many organisms).
Eventually, such viruses excise themselves from their host cell's DNA and accelerate viral reproduction to infect more cells. But the process of excising viral DNA from the host DNA is not perfect and, rarely, genes from the host cell are accidentally packaged into new infectious viral particles. When another cell, potentially in another species, is infected with viruses containing genes from their former host, the former host's genes can integrate into the new cell's genome along with the rest of the viral DNA. This effectively transfers the genes from one individual to another, unrelated individual (hence the name "horizontal" gene transfer, as opposed to "vertical" gene transfer from parent to offspring). This process is pretty rare among multicellular eukaryotes (including corals and us), but is very common in bacteria.
Again, I've never seen any evidence that this is occurring in corals, but I've read reports that corals can be infected by a number of viruses so horizontal gene transfer of this type may be possible.
It is also worth noting that if you're talking about color "transfer" between two different color morphs of the same species of coral when the two strains are in contact, you may be referring to chimeric or grafted coral colonies like this Montipora capricornis:
This can occur naturally if two strains of the same species are in contact and are somatically compatible (similar to having the same blood or tissue types). In these cases, it can appear that GFP or other pigments are spreading from one coral to another, when in fact two corals are just growing together in one colony. Similar processes can occur in other colonial organisms (like colonial ascidians, fungi, and some plants), and what happens to such chimeric colonies is a very interesting subject. Competition and parasitism between multiple genotypes inhabiting one body may have contributed to the evolution of our immune systems and of sexual reproduction.
@gaberosenfield Thanks for that! I'd imagined it would be something similar to that, but - since all the GFP work I've done has been knock-ins in a controlled lab setting - I was really curious to see if the speaker had lined out a mechanism for how this might've happened, since I recognize how unlikely/"odd" this is in the wild. I was also trying to figure out if it was possibly Renilla GFP, since I think the distribution of sea pansies versus A. victoria would make a bit more sense for Renilla GFP to be the culprit (if this is what's happening).
Side note: excellent writing conveying science to a non-technical audience, by the way. That's not a skill that many scientists have (or care to develop), and is immensely valuable if you choose to pursue a career outside the bench!
Side note: excellent writing conveying science to a non-technical audience, by the way. That's not a skill that many scientists have (or care to develop), and is immensely valuable if you choose to pursue a career outside the bench!
gaberosenfield
Guest
Thanks for the compliment @IOnceWasLegend! Given the current economic situation and the insanely competitive nature of the academic job market these days, I may need this skill... Thanks to BAR for letting me practice with/on you!
I would guess that if genes for GFP are spreading to corals, the source is probably other corals nearby. Many corals and other cnidarians (besides A. victoria) already encode GFP homologs, and most horizontal gene transfer mechanisms either rely on frequent close contact between individuals or on infection with viruses or other infectious agents that usually have restricted host ranges (i.e. they can only infect a few closely related groups of organisms).
Coral reefer
Past President
From what I recall, although it’s been near ten years ago, the speaker in question was saying he thought one coral could expel it and another could injest it. Not saying this is possible or not, or even if I understood correctly at the time.
It does seem more likely for something of that nature to occur in a closed system than the ocean to me though.
The example they gave was people seeing monti setosa getting green pigments
It does seem more likely for something of that nature to occur in a closed system than the ocean to me though.
The example they gave was people seeing monti setosa getting green pigments
Interesting! Doing a quick google search. I managed to find this, and it seems like this may be somewhat common based on this statement from ORA (emphasis mine):
ORA said:
gaberosenfield
Guest
I would caution against calling this an "infection", as it is not clear that any infectious agent is involved. This may simply be the corals responding to some change in conditions by expressing genes for GFP (or another fluorescent protein/pigment) that they already had in their genomes, like how most humans respond to increased sunlight exposure by darkening our skin. In fact, one of the main hypotheses about why corals produce fluorescent pigments is that these pigments act as a sort of sunscreen.
Oh, interesting - corals actually have genes for various fluorescent proteins in their genome(s) already? It would make sense, I suppose, given the colors they exhibit under actinics, but that's something I'd never really thought about. Although I also wouldn't be surprised if we just don't know given how comparatively new next-gen seq/WGS is and how many different species of coral there are.
(Also noting that I did not claim it was an infection, that was just the article that I linked to.)
That was one of my first thoughts when I started first entertaining the possibility of reefkeeping, along with the possibility of trying to do a more 'uniform' transfection of individual polyps with Cas9, sgRNA, and cassettes of various fluorescent proteins. I've not looked too deeply into it, but I'd guess the challenge would be there being so many different species of coral and not having all of their genomes mapped out that well, so having to re-optimize sgRNAs for each type of coral.
Also the concentration of salts in the transfection process, and how long the coral would be capable of tolerating suboptimal conditions that'd be more favorable to the transfection reagent.