Tridacna Clam Lighting Needs - Croceas CAN NOT survive T5s

candycane

Active Member
long term.
Croceas
- where they should belong.
The patches that are all over the clam are called iridophores; those are made up of iridocytes which form smaller apparent "bumps" called iridosomal platelets. The colors around these little bumps (schemochromes) direct light into these areas. Croceas have them pretty much all over the mantle. These use PAR most of the time - I don't know of many things that use PAR energy exactly the same. Inside of these channels resides a certain CLADE of zooxanthellae. This clade of zooxanthellae is usually A(? - sometimes Cs) are both pretty high light intensity zooxanthellae.
Croceas have the ability to stack their "iridocytes" which usually is what differentiates them and Maximas from Squamosa, Derasa, Gigas, etc. After a short period of time, Croceas are usually going to be the Tridacna Clam with the "tallest" iridophores (after stacking as many as possible); as in the areas are going to be the tallest (like a plant stretching towards natural light rather then false light). That is the reason these sections are usually more visible, after time, on Croceas and not other Tridacnas. Zooxanthellae generate around these patches because the incoming light that is absorbed by them is concentrated to these areas. The “chrome” type colors that are seen on a Croceas’ mantle are similar to using tinfoil to direct light into a certain direction. They stack even taller under T5s because they are getting basically NONE of the radiation they ACTUALLY need.
The difference falls in the fact that because of the many more iridophores or platelets there-of, the MAA mycosporine-glycine that is housed inside the Croceas mantle, spends most of it's time absorbing certain UV light in order to create "sunscreens" to block out others. They can usually co-exist, but sometimes one can dominate the other if one is getting more of the food source that it is supposed to have. If there is not enough UV for MAAs to use, then the clam usually starts sucking in Iodine, and COULD cause the MAAs to perish.
Now onto the final reasoning behind Croceas and their light qualities. EVERYTHING has a pigment for a reason (as far as I know) this includes zooxanthellae. zooxanthellae may be a species of algae that produces amino-acids, sugars, blah blah blah for it's host, but that wouldn't explain why the zooxanthellae is brown.
Xanthophylls are the carotenoid pigments (brown) inside the zooxanthellae that that protect it from "over exposure" from certain types of UV
radiation (and even spectrums of light from what I have seen lately- I could be wrong). If the xanthophylls that reside within the zooxanthellae are not doing their job, and keep in mind they are probably 20x more densely populated in Croceas which have a higher need for light, then what will most likely happen? Same thing that happens if I have an algae outbreak in my aquarium and shut my lights off for a week.
Here's probably the worst-best example I could give. If there is a group of zooxanthellae and it is protected from over-exposure, or the exposure is balanced by either MAAs or Xanthophylls BOTH need certain forums of UV radiation or photosynthetically active radiation (PAR)
to do their job in certain quantities. The Zooxanthellae, somewhere down the chain, will lose its pigmentation because it is either not protected or it is overly protected. Now the reason that is differentiates with Croceas is because of their ZTS system (or whatever you want to call it). They are VERY densely populated with such a small area (number of iridophores spanned over the small size of the mantle), to capture the light that is needed (this should even hold true for halides in most cases). It's like putting out a single grain of sugar out for 4000 ants and what not.
I would think that the same thing holds true with ALL Corals, Clams, and Inverts. etc. that hold a certain a clade of zooxanthellae which produce certain forms of xanthophylls and MAAs. They BOTH need a certain form of UV Radiation or PAR Energy (usually both - like a machine) in order to keep the pigment of the Zooxanthellae and stop whatever it is from eventually probably passing. I just have never really seen a T5 lighting source with that much photosynthetically active radiation, that can project more then 3/4 of an inch through water, powerfully. A T5 bulbs greatest chance is usually in the 10K Range. That is usually highest blue between 400-475NM - I can probably get a flashlight to produce a spectrum of 400-475NMs; doesn't mean it is going to contain ANYWHERE near the amount of radiation that comes from a certain gas burning.
HORRIBLE Example: In the long, the use of inadequate lighting not producing enough radiation is like trying to run a car with only one of the wheels turning on a 4-wheel car.
Just like radiation can kill certain cells, others need it.
Jon R Mott
 
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