So if someone told you that the coral "food" that we buy, among otherthings, was a waste of money. Would you believe them? I had this clown, :evil: , at Seamax tell me that the polyp extention that I see on my sps is just a stimulation response and not a "feeding" response. Also that active feeding only accounts for 2% of the corals energy intake and photosynthises accounts for the other 98% of the corals "energy." I liked hearing this considering coral frenzy and coral foods of the like are not cheap. Is he feeding me a line of crap?
LOL sorry for the late reply Steven, it took me forever to find my clown costume, and I wanted to answer the post while wearing it
eace:
Ok so lets dig into it a bit. So you got two questions going on here, one is what folks in the hobby call polyp extension and the other feeding requirements, so lets tackle the polyp one first.
Polyp extension: So yes no matter what kind of coral you have polyp extension and thus retraction is just a stimulation responce. The coral polyp is used by the coral itself (varies between species and type) for alot of different things such as defence, aggresive offence, reproduction, feeding, sencing. So we never really know what is creating the coral to either extend or retract its polyps. Also this procedure can be in responce to a chemical reaction, these chemicals can come from prey, or chemicals from near by corals (off/def) or chemical stimulates set off by similar corals (perty time). Or it can be mechanical stimulas, such as something bumping into it or electrical stimulas. So you cant really look at polyp extension as the "Warm and Fuzzy" feeling that the coral must be happy, it could be a number of things or any combination of many things.
Feeding corals: This one is a pretty broad subject with all the differing types of corals out their, so I will just through out a general rule and then dig into SPS. SO the general rule I tell folks to follow is the "Tissue rule" . You can judge how much a coral needs out side source by how much tissue the coral has on it. So zoos are almost 100% tissue so you can then assume that they require alot of external food sources, on the opposite side of that is what we call SPS which only have a very tiny amount of tissue and thus require very little amounts of external food.
Ok SPS: SO as we know sps corals are very dependant on photosynthesis for the energy they require for all their processes. Basically thier zoox algae absorbs light protons and turn them into simple sugars and so on for transfer to the coral host. Studies show that up to 98% of their energy budget requirements are delivered to the corals via this process and the balance is supplimented through other means. SO lets look at this a little deeper. When any coral captures food they use what is called Nematocyst, which are basically barbed harpoons they shoot out and capture the food with, then they are able to retract this barb and then enclosed the hooked peice of food with in the polyp. So here is a picture of this Nemaocyst
So as you can see this is a nasty device, but in a sps the Nematocyst is not very developed, as in it does not even have barbs and it cannot shoot out the barb from itself like. Corals that rely of caputre have highly advanced Nematocyst like pictured above and many thousands of them. So barbless Nematocysts, and the inablity to launch them makes this a device they do not rely on. So for a SPS coral to capture food it would have to have the food randomly land directly into its Septa (basically its mouth) and then stay their long enough for the coral to envelop it. So very little chance of live food to do this as they would just swim away, a peice of food/detritus?? possibly but very little at best, definately not something a critter that has lived for millions of years to rely on.
So do SPS cature food?? Yep they do it in two seperate manners. One is through direct absorbsion through the SW that flows between its tissue and it skeliton, but this is very very little and most of that is used to lay down the lattice structure of its skeliton. The second method accounts for as much as 4 to 7% of it energy intake. This process is called mucus netting, Corals release an amount of mucus from just beneath its Septa, this mucus is a mixture of DOC's, lipids, aminos and excess carbon that is not used by the corals, or junk food for microscopic critters. When the coral lays out this mucus it is immediately attacked by bacteria and similar other critters, also it will capture small particules that happen to land on it. It then retracts this mucus into its digestive tract and then begins to process it. Now this mucus can be put out if the polyps are extended or not.
So here are some studies if you need to verify:
Falkowski, PG, Dubinsky, Z, Muscatine, L, Porter, JW, Light and bioenergetics of a symbiotic coral. Bioscience, 1984, pp 705–709(34)
Muscatine, L. Porter, JW, Reef corals: mutualistic symbioses adapted to nutrient-poor environments. Bioscience, 1977, pp 454– 460(27)
Edmunds, PJ, Davies, SP, An energy budget for Porites porites (Scleractinia). Mar. Biol, 1986, pp 339– 347(92)
Ok so this brings us back to feeding sps. From looking at scientific studies and understanding the corals biology we can see that they derive a very small percentage of their food source from external feeding. We also can see that when it comes to capture of food they use a slime netting process and that process is random and is based when the coral has enough slime material produced to put it out, so their schedule not ours. Now when we feed various commercal products into our tank we know this comes at a price and this price (other the dollars) is nutrient loading in a system that is usually nutrient loaded to start with, so is it worth it?? For me no, the fact they produce up to 98% of their energy budget via photosynthesis and capture between 4 to 7% via slime netting. Also I know that I feed my fish and I know that they constantly poop and that they poop at least 90% of what they intake, I know that their is plenty of that detritus floating around in the tank at any given time to land on that slime, I also know that my tank is loaded with bacteria and they they will attack that slime on mass and that the coral is biological designed to digest bacteria very easy.
Anyway sorry for the long winded reply I am now going to take this clown nose off as I cant breath
Mojo
