Some Excellent Reading

[piscivorous]

So with all of that said.....who here feeds their larger clams? What and how and how often do you feed them?

[Kalkbreath]

Im reprinting this from another thread because I think it will reach a larger audience here.....
I'll offer my two scutes on this to feed or not to feed debate.
I talk with three major Tridacna clam farmers often .
None of them feed their farm clams with any form of supplemental plankton.
They all do however, when they want to get them to grow faster ...feed with nitrogen/ammonia fertilizer pellets.
But they understand that they are actually feeding the tiny zooxanthella inside the clams , more so then the clams themselves.
They also don't suggest hobbyists feed clams in their aquarium anything other then ammonia in the form of fish waste.
There are many studies comparing clam growth with and without fish in the system. Fishless systems always yield slower growth.
It's the constant supply of ammonia feeding the zooxanthella which is important.
I have studied clams for a few years now; under the microscope, one can clearly witness the zooxanthella inside a clam's blood stream and stomach along with amoebsites which farm the zooxanthella, a little bacteria and not much else.....
But oddly enough , I have never found plankton?[neither zoo plankton or phytoplankton] EVEN after days of target feeding.
It seems that when fed, clams do filter out plankton from the water and it can be found concentrated on their gills. But with filter feeders, they filter every thing in the water, so the plankton gets stuck to their gills just like every thing else in the aquarium water.
[ Just like filter floss would stain out indiscriminately ]
Just because the clam filters the water , does not mean the clam is eating the plankton.
In order to be eaten , the clam must ingest the plankton.
Ingesting food is carried out when the clams gills allow only certain substances to pass through their membranes. Kinda like a reverse osmosis filter.
Most of what a tridacna clam filters with its gills is ultimately pooped out or coughed up before it ever gets into the clams digestive system.
Clams dont even let non motile zooxanthella past their gills.
Preferring zooxanthella with tails. It is thought that its the swimming action of the zoos tails that triggers the opening of the gates so to speak and into its stomach.
Some feel that yes, clams do seem to have the appropriate mouth parts to feed and therefor nature would not of designed them with such mouth parts for feeding if they did not intend to make use these feeding abilities.....
BUT! One could ague that the sole use for this feeding ability is to take in Zooxanthella .
Afterall, without his ability to feed on Zooxanthella , baby clams would die . Baby clams are not born with zooxanthella inside their body.
Giant clams may simply use this feeding ability as a way to inoculate themselves with zooxanthella.
As humans, we have several uder utilized organs, such as our tonsils, appendix and for many of us , our "better judgement"

Furthermore, There are reports of clams choking on too much plankton paste and it clogging their gills and clams dying from too much of a good thing in over fed, low pH,nutrient rich aquariums.from overfeeding. Contrary to a misconception, clams dont like high Nitrate levels.
I at times wonder if the bad rap small calms get for being difficult to raise, comes more from hobbyists killing small clams by over feeding the tank resulting in high nitrates,a lowered pH, and otherwise less then ideal tank conditions. ........then these young clams would do if just treated like any other coral or anemone, with proper water conditions and a well cycled tank?

[critterkeeper]

Also copied from the other post:

Kalkbreath wrote:

"I have studied clams for a few years now; under the microscope, one can clearly witness the zooxanthella inside a clam's blood stream... I have never found plankton?[neither zoo plankton or phytoplankton] EVEN after days of target feeding... Ingesting food is carried out when the clams gills allow only certain substances to pass through their membranes. "

Zoox aren't found in the bloodstream, they are kept in a specialized system of tubes called the zooxanthellal tubular system. And the gills don't let things "pass through their membranes". Particulates are sorted and passed to the labial palps, then injested by the mouth, which leads to the stomach. Also, numerous studies have found phyto in their stomachs, as well as some other things, including zooplankton.

Really, this entire subject is covered in great detail in my book, but I can throw this in too. I was successfully keeping clams in 1993 - before there was any such thing as phyto in a bottle. DT's hadn't even been "invented" yet - it came out in 1996. I'd never even heard of trying to feed them anything - and they didn't die. I started a maintenance business in 1996 and had numerous clams in my own and customers tanks - and never used phyto in any of them, until I started using live sand beds in a few tanks in maybe 1999. Never noticed any change in growth/survival of clams. That's how I knew DT's/Shimek's article was wrong before I ever looked at any of the references. Yes, it is complete BS.

[Kalkbreath]

. [/B][/QUOTE]

Originally posted by critterkeeper
Also copied from the other post:



Zoox aren't found in the bloodstream, they are kept in a specialized system of tubes called the zooxanthellal tubular system. And the gills don't let things "pass through their membranes". Particulates are sorted and passed to the labial palps, then ingested by the mouth, which leads to the stomach. Also, numerous studies have found phyto in their stomachs, as well as some other things, including zooplankton.

.

That's what they say , but I'm not so sure " they" understand what's really happening.
What do "they" say about how only SYMBIOTIC DINOFLAGELLATES (ZOOXANTHELLAE) are allowed to pass into the zooxanthellal tubular.
Whats to prevent other taken in algae from taking up residence inside the tubular system and out competing the zooxanthella?
For instance; how does a clam distinguish a regular dinoflagella from the a SYMBIOTIC DINOFLAGELLATES (ZOOXANTHELLAE) variety?
Only allowing this one species of Dino to enter the tubular vessels?
Most agree that the clam benefits off the byproducts {sugars} from the zooxanthella and this "fuel" is responsible for most of the clams respiration.
But what mechanism feeds the Zooxanthella? Various studies have shown that no chlorophyll decomposition products are found in any freshly prepared zooxanthellae preparations. So it seems that the zooxanthella dont directly fed on other Algae. This would surely seem to suggest that the clams' stomach is not directly responsible for feeding the zooxanthella .
It seem more likely that the clam is filtering anything it can out of the water and extracting ammonia to feed its zooxanthella.
When I walk out into the spring air during pollen season , I inadvertently take in a sizable amount of plant spores with my respiration. Could it be that a clam simply can t help but filter in plankton while it breaths. Even though it has no end use for the Plankton.
I think more complete examination of this complex feeding cycle needs to be conducted.

[critterkeeper]

Read:

Mansour, K. 1946a. Communication between the dorsal edge of the mantle and the stomach in Tridacna. Nature (London) 157:844.

Norton, J.H., M.A. Shepherd, H.M. Long, and W.K. Fitt. 1992. The zooxanthellal tubular system in the giant clam. Biological Bulletin 183:503-506.

Norton J.H. and G. Jones. 1992. The Giant Clam: An Anatomical and Histological Atlas. ACIAR Monograph Series No. 14, Canberra. 142pp.

Fitt, W.K., G.A. Heslinga, and T.C. Watson. 1993. Utilization of dissolved inorganic nutrients in growth and mariculture of the tridacnid clam Tridacna derasa. Aquaculture 109:27-38.

Farmer, M.A., W.K. Fitt, and R.K. Trench. 2001. Morphology of the symbiosis between Corculum cardissa (Mollusca: Bivalvia) and Symbiodinium corculorum (Dinophyceae) Biological Bulletin 200:336-343.

Fatherree, J. W. 2006. Giant Clams in the Sea and the Aquarium. Liquid Medium. Tampa, FL. 227pp.

Fankboner, P.V. 1971b. Intracellular digestion of symbiotic zooxanthellae by host amoebocytes in giant clams (Bivalvia: Tridacnidae), with a note on the nutritional role of the hypertrophied siphonal epidermis. Biological Bulletin 141:222-234.

Then you'll understand... I think "they" know what they're talking about.

[Kalkbreath]

I seem to have missed where they answered my questions.
How does the clam choose which one celled algae to let in and which to not let in ?
How does the clam prevent other algae from co existing within the Mantle and tubular system?
How does a clam choose what it eats?
Does a clam actually have digestive juices, or does its stomach contents simply rot and give off ammonia to feed the zooxanthella?

[DaveBien]

I think I'll believe the experts......

[area]

how long would it take for a clam to die without phytoplankton.cause I think I just lost my clam.

[Snarkys]

IMHO a clam is more likely to be stressed and die from a lack of lighting or calcium and alkalinity than lack of capturable pray .

If you have these covered i might look at lack of pray as a source.