Here is a VERY interesting article on clams. I'll post it and the link to it as well.
http://www.animalnetwork.com/fish2/a...ll/default.asp
Here are a bunch of articles that I highly recommend everyone wanting or owning clams to read.
http://www.reefs.org/library/aquariu...alf_Shell.html
Gamete Release by Giant Clams in Aquaria
Giant clams have often been observed to release egg cells and sperm in aquaria. This is undoubtedly an interesting event because gamete release is a common occurrence that normally involves several clam individuals. Under natural conditions, this enables the clams to exchange their genetic material to produce offspring with good environmental adaptations.
But, aside from being fascinating, gamete release in the confines of our aquaria sometimes brings problems for the aquarist by causing a drastic decrease in water quality, which can be a threat to other tank inhabitants. It can cause disaster among fish and invertebrates and even among the clams themselves. It is therefore important for the aquarist to pay scrupulous attention to the water quality and take some counter measures listed below whenever necessary.
Some frequently asked questions about this topic are: What triggers gamete release in clams in an aquarium? Why do many clams in a reef tank join in? Is it true that clams used to die after gamete release? Is it harmful for the fish to feed on the egg cells? What can I do to prevent the water quality from deteriorating after gamete release?
What triggers gamete release in aquaria?
As with other creatures, gamete release serves to maintain the species. Under good conditions in nature, this normally depends on the presence of mature egg cells in the gonadal tissues of at least one adult clam within the clam colony. This clam will start releasing its gametes and simultaneously release a hormone-like substance to inform other giant clams about the event. Because the giant clams are simultaneous hermaphrodites, they can produce sperm and egg cells at the same time, provided they are fully mature. Many of the other colony-mates will detect the “biochemical message” and join the spawning event.
Because clams reach their male maturity at a relatively young age and small shell size, a clam colony always includes many more sperm-producing clams than those that produce eggs. Therefore, most of the milky clouds that arise from the little excurrent syphons of a clam consist of sperm. As mentioned above, this is how it all starts under good conditions in nature. But sometimes, giant clams also spawn sperm and eggs after rapid changes of environmental conditions or after strong environmental stress. This can be due to overheating from sunlight when the clams become dry during ebb tide, exposure to freshwater during a strong rain at ebb tide or other environmental changes that make the survival of the clam colony questionable. In this case, the clams sometimes react to the irritation by spontaneously releasing gametes. This is meant to ensure the survival of the colony and the species in case the clams die because of the environmental stress. They release egg cells and sperm to produce larvae that can settle near the colony or elsewhere and grow to adult clams, thus forming a new clam generation.
In the artificial breeding of clams, this strategy can even help make the clams spawn egg cells (Knop 1996). The clams are placed in the sun for 20 or 30 minutes, sometimes even longer, imitating an ebb tide on a hot summer day. If one of the clams has mature egg cells, it is likely they will be released when the clam is placed back in the water. The spawning of clams after events of stress has proven to be a successful strategy, at least under natural conditions. However, we have frequently observed problems with this strategy when importing clams from a hatchery. Out of a hundred clams, most of the time there will be one or two clams that are irritated due to transportation stress. They will release gametes as soon as they are put into the water. This normally triggers gamete release in many other clams, and after a short period of time, the stocking tank looks like a giant glass of milk. This causes additional stress for the clams, which is quite unfortunate right after the stress of transport.
This situation is also often observed in reef aquaria. Small environmental changes in the aquarium can trigger a clam to release egg cells or sperm. This may be caused by heat stress during summer, using freshwater to top off the tank from evaporation or doing a partial water change. Soon other giant clams in that tank will join the spawning event and the tank water will become turbid.
In other cases, the environmental conditions in the aquarium did not change at all prior to the spawning event. In those cases, it is likely that one of the clams did not adapt to the captive environment and was about to die for whatever reason — perhaps insufficient illumination, bad water quality, harassement of fishes — among other reasons. Before dying, this clam expelled sperm and/or egg cells. If this clam should eventually die, the unexperienced aquarist may come to the opinion that it died because of gamete release, while the truth is just the other way around: it has released gametes because of the nearing of death.
Generally, many fish that are commonly kept in the tank with the clams will be very happy about the egg cells. They feed on them like crazy, especially the smaller planctivorous fishes, such as several Anthias or Chromis species. Unlike the egg cells released by some fish species that are known to be poisonous, like the eggs of the scooter blenny (Synchiropus ocellatus), tridacnid clam eggs are a harmless food for aquarium fish. But this joy is not long lasting, because soon the gametes start to die. Because the egg cells and sperm have all been exposed to the water for about the same period of time, many of these die more or less simultaneously. This causes the water to become polluted and there is a remarkable decrease in oxygen. Under good aquarium conditions, this does not necessarily pose a threat for the reef tank community, but this is strongly dependent on the amount of water, equipment such as protein skimmers or filtration with granular activated carbon, as well as other factors like the water conditions or the number and size of fish kept in the tank. Another important factor is the number and size of clams that have released gametes.
It is impossible to give an estimate about the risk of damage for the tank inhabitants. In every case of a giant clam spawning, the aquarist should be prepared to take some countermeasures in order to prevent the aquarium community from being harmed. Here are a few things you can do to minimize the risk:
1) If the large size of the clam expelling gametes makes you worried about the water conditions (e.g., an adult T. squamosa with a 40-centimeter [15-inch] long shell in a relatively small tank) try to transfer the clam into another tank or a pail or bucket during spawning. Fill the bucket with aquarium water and place the clam in there until the gamete release has stopped. It is a good idea to change the water in this bucket once or twice if gamete release takes a long period of time. Also, you should monitor the water temperature and provide water circulation, preferably with an airstone fed by an air pump. The water taken out of your tank will be replaced by new artificial seawater. Once the clam has finished gamete release, place it back in the display tank in the same location it was before the event.
2) The same thing is advisable if gamete release takes place in a dealer’s clam stocking tank. This is especially important directly after the importation of clams, because the clams have been weakened during transportation and further stress caused by decreasing water conditions can be harmful to the mollusks. If one of the clams starts expelling sperm or egg cells after being introduced to the stocking tank, remove it as soon as you notice it. If other clams join in, also remove those from the stocking tank and place them in a separate container, while providing the conditions mentioned above (water temperature, aeration). This can prevent the stocking tank’s water conditions from deteriorating. After my experiences with newly imported clams of several species and sizes, the risk of having a gamete release is relatively big. When importing 500 clams at a time and placing them in five stocking tanks with 100 clams in each tank, most of the time we experience a spawning event in at least one of the tanks, sometimes even in two tanks. With clams of various sizes, the number of clams joining the gamete release will mostly be around five to 20 individuals per stocking tank. Transfering the spawning clams to different containers during gamete release enables you to leave the other clams alone without a further change of the aquarium conditions.
3) If you have a huge clam spawning in a relatively small tank and you cannot remove the clam, there is a simple way to syphon out the gametes before they can spread in the tank. What you will need for this is a funnel, a flexible tube and a pail. Connect the tube to the funnel and place the end of the tube in the pail. Now hold the funnel over the spawning clam and suck at the end of the tube in order to create a water flow down to the pail. Once the water is flowing, stop the flow by pressing the tube. Once you see the clam filling its excurrent chamber with water in order to blow gametes through the excurrent syphon, open the tube. The funnel will collect most of the gametes and transport them into the bucket.
4) When you observe giant clams spawning in your tank, make sure you have enough supply of fresh saltwater to perform a partial water exchange of 10 to 20 percent of the tank volume. This may not be necessary, but you should be prepared for it. (This is also important when corals spawn in a closed tank system. Experiences of aquarists have shown that the water pollution and decrease of water quality seems to be similar to the clam spawning.)
5) Add an extra portion of activated carbon to the system.
6) Make sure the protein skimmer is working well.
7) Install cotton media to the filter. This filter material has the advantage of having floating particles adhere to it due to its static charge, which can be helpful to free the water of fine floating matter. But to achive this, the water flow should be relatively slow. It is best to let the water pass through the cotton just by gravity and not be forced by the suction or blowing force of a water pump. Take a plastic cup, perforate it ia number of times and locate it on top of the aquarium. Direct the water flow coming from a small pump, a proteing skimmer or some other device in a way that lets it pass through the cup (and filter cotton) by gravity flow and then run back into the aquarium. You can increase the effectiveness of this filtration method by passing the water through an ultraviolet sterilizer prior to the filter cotton.
8) In case the fish start to breathe heavily, do a partial water change of 10 to 20 percent.
9) After the spawning event is over, you should check the condition of all clams in case one of the clams started the spawning event prior to its own death. If the clam has have died and the soft tissues start to decompose overnight, this will lead to a further decrease in water quality and it might give you an undesireable surprise next morning. If you are doubtful about the condition of the clam, and if the incurrent syphon is gaping and it does not show a reaction to touching the syphonal mantle, remove it for a day and put it into a separate tank (with aquarium water and aeration). This does not necessarily mean it will die. I have seen many clams extremely stressed by spawning activity that were “gaping” and showing no mantle retraction when touched. After a day or two everything went back to normal. But, if the tank system is small, it may be better to be on the safe side and set the clam aside for the coming night if you are doubtful about its condition.