So, a tridacnid clam doesn’t have to rely on filter-feeding when kept under optimal conditions. zebra, encrusted with coralline algae.Īs long as a tridacnid clam gets plenty of light, these algae being maintained within its body can make more food then they need for themselves and can donate the excess to the clam host. I cannot identify the two small ones on the left to the species level, but the one on the right is the common turkey wing clam, A. This is why tridacnids are known as zooxanthellate clams, while the rest are azooxanthellate.Īrc clams (Arca spp.) like these are also found on aquacultured live rock at times. While they can and often do filter-feed, they also contain large complements of live zooxanthellae in their extendable soft tissues, which are the same single-celled algae that corals utilize. Tridacnid clams are a bit different than the rest though, as they can cover their nutritional needs in more than one way. However, for the most part they rely on phytoplankton, specifically. As far as the digestible material goes, many clams can actually use a variety of phytoplankton, zooplankton, and bacteria, but can also make use of some detritus, too. Various types of particles are also sorted out to some degree along the way to the mouth, and most of the indigestible/unsuitable stuff is discarded. As these waterborne particles pass over the gills, many of them stick to their surfaces and are then moved along by cilia into grooves that ultimately direct the particles to a clam’s mouth. And, by creating such currents, they also draw in food particles along with the water. They’re covered by numerous, microscopic hair-like structures called cilia, which can move back and forth rhythmically to create a current of water that flows over the gills for gas exchange. Their gills are finely branched structures that take in oxygen and give off carbon dioxide, but they’re responsible for the capture of food particles, too. To cover their nutritional needs, the vast majority of clams strain various sorts of plankton from the surrounding waters, making them filter-feeders by definition. Water is taken in through the inhalent siphon in the background and leaves through the exhalent siphon in the foreground. This one has opened its valves a bit and has extended its tube-like siphons, which are the openings where water is moved into the clam and over its gills, and then back out minus any captured food particles. Here you can see a jewel box clam (Chama macerophylla), a species often found on aquacultured live rock from Florida. So, they’re far more complicated than they might seem. They have complex gills, a mouth, stomach, and intestines, a heart, kidneys, ovaries and/or testes, a well-developed (albeit brainless) nervous system, and more. However, they actually have a full set of well-developed specialized organs. And with that said, I want to get back to complexities for a moment.Ĭlams don’t appear to be very complicated animals while just sitting around on the bottom of the sea or an aquarium. However, I’ll be sticking to the epifaunal clams, which are the ones that live on the bottom rather than in it, or attach themselves to rocks, macroalgae, or other invertebrates, such as corals, etc. Some of them, such as the infaunal clams, live their lives buried in the substrate, too. Some of these molluscs swim around all the time while some crawl about. This phylum is also home to the snails, cephalopods, and a several other invertebrates that are far more complex than the corals and their kin. While corals are members of the Phylum Cnidaria and are relatively simple animals, clams belong to the Phylum Mollusca. However, clams are about as distantly related to corals as an animal can be. Like coral skeletons, these valves are composed of calcium carbonate, and are produced by the living tissues of the clam. Each half of a clam’s shell is properly called a valve, and the “bi” part is obviously added to it because there are two of them. I’ll also give you some information about a few types of clam that are commonly seen in reef environments and sometimes for sale. So, I want to provide you with some general information about the biology of clams and some specific information about why they can be difficult to keep alive long-term in aquariums. These include a variety of scallops and oysters, and a few other species, none of which are well-suited for aquarium life primarily due to their demanding dietary needs. But, there are a few non-tridacnid clams that are also available to us, some that hitchhike into our aquariums on live rock and such, and some that just show up seemingly from nowhere from time to time, too. Most reef aquarium keepers know something about the commonly-offered tridacnids, otherwise known as the giant clams.
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