And then, of course, there is competition from other filter-feeders. Of all the planktonic organisms in aquarium water, however, nanoplankton are the first to be removed/killed by UV sterilization and protein skimming. Blooms of heterotrophic bacterioplankton, for example, take place for short periods of time following carbon dosing. Some of this food certainly is produced in situ, as most systems have at least minimal amounts of bacteria and phytoplankton in the water column. In just a few cases, sponges can harbor zooxanthellate algae much like corals and tridacnid clams.Īside from good water quality and strong water movement, captive sponges need lots and lots of planktonic foods of the appropriate size. In some cases, minute bits of particulate organic matter may be consumed. This group includes bacteria and the smallest species of phytoplankton. The vast majority of sponges are nanoplanktivores, feeding upon the tiniest of plankton. A sponge must, on average, filter approximately 275 gallons of water to capture enough food to gain three ounces of biomass. It is the choanocyte that pushes water and traps food particles it is the amoebocyte that engulfs and digests them. Thus, to eat, they must push tiny morsels to and through their bodies via miniscule, self-generated water currents. Aside from the frenetic activity of their many flagella, sponges are almost completely incapable of any kind of deliberate movement. Sponges are (with few exceptions) filter-feeders. But the body plan of all sponges is very much centered on their feeding activity. More advanced sponges exhibit modest structural complexity in the form of distinct body shapes (candelabras, vases, etc.), folded body walls, highly branched water canals, multiple oscula, etc. From there, water exits through a duct called an osculum.Īlright, it can get a little bit more complicated than that. The sponge draws water into itself through these pores whereupon it enters a central cavity called a spongocoel. The body is more or less composed of just two kinds of cells, the flagellated choanocytes and the wandering amoebocytes. The simplest of sponge bodies are composed of a hollow sack or sheet that is perforated with numerous tiny pores. That being said, individual cells can not only sense and react to environmental stimuli but communicate with other cells. In a lot of ways, sponges are really just a big pile of loosely associated cells. In fact, overall, their cells are so unspecialized that they lack (at least in the opinion of some biologists) true tissues. These very primitive creatures are so simple in structure that they really are a lot more like colonies than distinct organisms. Of all animals, sponges (Phylum Porifera) are most closely related to the colonial choanoflagellates that are the progenitors of the animal kingdom. To address this concern, it may be helpful to understand the basic anatomy of these “animals” and how they feed. But the biggest longstanding concern for captive sponges is nutrition. air exposure) dooms an otherwise healthy specimen before it even reaches a retailer. Other reasons are not always so obvious too often, improper harvesting/handling practices (e.g. For example, a single pomacanthid angelfish can consume a large sponge in a matter of days. Sometimes, it’s as simple as bad pairing. This low success rate is attributable to several things. Despite their sometimes stunning beauty, they are unusual to aquarists for one reason: They have a really, really bad record of survivability in captivity. If anything, they are rather poorly represented in the aquarium hobby. Indeed, they are found in great abundance and diversity on most coral reefs. Sponges, at least as a group, are not rare in any way. These developments will surely result in a much greater selection and availability of “oddball” aquarium livestock in coming years. Many marine creatures (especially filter-feeding invertebrates like sponges) that were once deemed difficult or even impossible to keep are now cultured with regularity. Much of this owes to progress in the area of foods and feeding. Coral reef aquaria, and the science of maintaining them, have advanced by leaps and bounds in the last decade.
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