Identity

For a variety of reasons, aquarists often want to attach names of one sort or another to the animals in their systems. Generally, the way this is done is that the hobbyist goes to some reference and finds a picture of an organism that "looks" like the one in his system and, "Presto! The organism has been identified." While this approach will work moderately well with fishes, some snails, many echinoderms and some shrimps, it doesn't work worth a squat with the sponges.

For such a visually comparative methodology to be successfully applied, the organisms within the species in question must have little variation in shape or color from one individual to the next and there must be few other species with similar morphologies. We all know that organisms within a species vary somewhat in morphological characteristics such as color and shape. The example of this type of variability with which most of us are probably familiaris our own species. It is obvious that not all humans look alike, but experience has shown that all human shapes and sizes can successfully interbreed. At the same time, it is also evident that there is little variation in appearance across the whole human species. This follows from the type of animal that we are; all vertebrates have an adult shape that is relatively consistent across their species. Most animals are similar in this regard; within a species, one individual looks pretty much like every other individual.

A number of animal groups, however, do things very differently. Growth in these animals doesn't lead to a defined adult shape or morphology. While their growth is always governed by some genetically determined rules, these rules don't necessarily lead to a defined adult size or shape. Put another way, even though there will be some structural similarities, no two animals in the species will have the same shape. Within such marine species, the growth form is often determined by environmental variables such as water currents or light, and the final adult shape is due probably as much to the environment as it is to the animal's inherited characteristics. If several species have the same basic genetic rules for growth, individuals from those species will, for all intents and purposes, look identical if they are grown under similar environmental conditions. Sponges are animals that grow this way, and within every geographic region many species often appear, to the casual observer, to be identical. The problem is compounded, however, when comparing species from many different geographic regions. Unless the potential identifier has a great degree of familiarity with a specific region, it becomes well nigh impossible to identify such animals.

Figure 1. Sigmadocia sp. This temperate sponge was growing in the lee of a rock and shows the effects of changing currents on colonial shape. As the colony grew up into an area of vigorous currents (to the upper right), its morphology changed from a massive encrusting form to one with thin linear branches. This sponge was collected and identified in my laboratory. Identification by appearance alone was impossible.

Sponge species, as whole, are impossible to identify by casual comparison to some photograph or illustration. It is possible to identify the animals, of course; it just usually cannot be done by simply comparing their gross appearance. That having been said, every geographic region has a number of sponges that are easily identifiable in this manner. Unfortunately, with few exceptions, these easily identifiable animals are not generally the ones that are able to be kept in marine aquaria. Within the sponge groups that I discussed last month, probably the ones with the most consistent apparent morphologies are the hexactinellids (the glass sponges) and the calcareous sponges. In the most diverse, and most common, sponge group, the demosponges, most species are impossible to identify by comparison with photographs.

Obviously, the plasticity of shape seen in most demosponges leads to the obvious question, "If these animals cannot be identified to species simply by looking at them, how are they identified?" The answer is relatively straightforward, actually, as is the identification process. Some of the animal's internal structures must be compared to the corresponding structures found in other similar animals. The earliest taxonomists recognized the variability of sponge shape as an impediment to these animals' easy identification and characterization, and it was realized early on that other types of criteria would be necessary to reliably distinguish between sponges.

In addition to the variability of sponge shape, another problem was the basic simplicity of sponges. Sponges simply have few structures on their bodies that can be used for identification. Animals such as fishes have all sorts of external characteristics that can be used to distinguish between species. They can vary in color, body shape, fin shape, fin length, presence or absence of scales, the shapes of scales, the presence of spines, spine shape, and so on ad infinitum. In contrast, sponges are blobs with holes of several different sizes in them. The paucity of structures makes them difficult to easily characterize - and this has lead to many problems with their taxonomy. About the only consistent structures in most sponges are their spicules. Consequently, the sizes, shapes, and relative abundances of these microscopic skeletal structures are the structures used to distinguish between various sponge species.

By the way, hobbyists are not the only people who have problems identifying sponges; many sponge experts have had problems as well, and that has lead to everybody subsequent to them having problems. As an example of this confusion, consider the common intertidal sponge Ophlitaspongia pennata found along the Pacific Coast of North America. This species is quite abundant, and is commonly found in the lower intertidal zone. It was originally described by Lambe in 1893. He described the spicular array that he considered to be diagnostic of the species. He also described it as having a specific and characteristic morphology in which the sponge's water channels were quite evident. Few shallow water sponges along the Pacific Coast have a characteristic morphology, but for several decades it was thought that Ophlitaspongia was one of them. Virtually all examples of this sponge found in shallow water show the characteristic surface with the visible water channel system. Ophlitaspongia is also notable for one other reason; it is a brilliant red, and that coloration makes it strikingly obvious. It is the only red sponge common throughout the region. Although there was another red sponge, it was considered to be rare and was collected from deeper waters. This other sponge was obviously not Ophlitaspongia as it had 1) a different appearance, 2) a different array of internal spicules and 3) was found in a different habitat. The rare red sponge was essentially impossible to identify with the available literature. It had a different spicule array than what was known from the area's other sponges. Because of the differences from Ophlitaspongia, it appeared to be a species that was "new to science." However, Ophlitaspongia pennata in the intertidal zone is almost always found with a small nudibranch, Rostanga pulchra, grazing on it. This little nudibranch is rarely found in deeper water, but that wasn't known at the time. It wasn't until some students started to examine the relationship between this particular nudibranch and its prey that it became evident that the "characteristic" appearance of the sponge was the result of having been partially eaten by the snail. Upon removal of the nudibranch from the sponge, the sponge's shape and spicule arrangement changed quite drastically, and it turned out that the rare deep-water red sponge was simply Ophlitaspongia growing in the absence of predation (Bakus, 1966; Anderson, 1971).

Step 1. To What Major Group Do the Sponges Belong?

The first thing anyone identifying sponges has to do is to identify the animal to its basic group. In other words, "Is the sponge a hexactinellid, a demosponge or a calcareous sponge?" Hexactinellids are rare in shallow water, and are almost never seen on coral reefs, so most hobbyists can eliminate that choice immediately; nevertheless, in the unlikely event that one could turn up, I have included them in this discussion.

To determine a sponge's major group, first place a small piece of it in a small glass container (a vial or very small jar works well). Add enough chlorine bleach to cover it, then shake it well and let it stand for a while. When the sample quits bubbling, use a pipette to remove the fluid, being careful not remove any of the residue at the bottom. If the piece dissolves completely and no residue remains, the sponge is a demosponge. Some demosponges (such as bath sponges) will leave no residue at all after the bleach treatment.

• If there was residue, rinse the sample with tap or RO/DI water by squirting in some water, agitating the sample and then letting the residue settle. After this, pipette out all but a small bit of water and the residue. Add a few drops of muriatic acid (hydrochloric acid), available at hardware or swimming pool-supply stores. Be careful not to get any of the acid on you or your clothing; this stuff burns! If the residue fizzes, it is made of calcium carbonate and you have a calcareous sponge.

• If the residue does not fizz, you have either a demosponge or a glass sponge. Demosponges will leave a residue of fine powered or slivered glass fragments. These tend to look like fine sand in the container and are the spicules. Once having confirmed that it is a demosponge, your job is over. There is no way to accurately identify the sponge further without microscopic examination of its spicules, coupled with recourse to the taxonomic literature, and this is an ugly job, at best. If the spicules have remained in a more-or-less rigid network or lattice, you may have a hexactinellid or glass sponge. If you think your specimen is a hexactinellid, and you want to verify this, let it dry out in the glass container and send me the residue, and I will be glad to confirm it.

Step 2a. Identification of Demosponges to Species

If you have determined your sponge's major group and you are a brave, or foolhardy, soul, you might wish to try to determine its species. This may be a very difficult task, however; rather like the old saying about exceptions proving the rule, some demosponges ARE easy to identify. These are sponges whose the colony has a more-or-less defined shape and color. In tropical areas these are generally larger sponges and are found in high current areas. As such, they are not suitable for reef aquaria; they are either too big or they require both high currents and laminar water flow. Although many reef aquaria seem, at least to aquarists, to have impressive water turn-over rates, these rates are often small compared to the several knot currents that flow along, and over, reefs at flood tides. Additionally, virtually all aquaria are dominated by turbulent flow regimes, and these flow patterns are not suitable for many sponges. The natural environment's high water velocities and consistent laminar flow have worked as naturally selective agents, however, and this has resulted in the distinctive shapes of many of these sponges. These sponges may sometimes be identified by comparison with published images, provided, of course, that those images were correctly identified in the first place. Generally, large and distinctive sponges can be identified reasonably well by comparison to photographic guides AS LONG AS THE SPECIMEN'S GEOGRAPHIC ORIGIN IS KNOWN. Knowing the geographic locality is important, as different species from different regions may look effectively identical in photographs.

Figure 4. A couple of sponges that are identifiable by comparison to photographs: the purple sponges are Niphates ramosa and the orange sponges are a species of Agelus. They were identified by H. Reiswig, one of the premier workers studying sponges. The individual Niphates colonies are over an inch in diameter and are unsuitable for reef aquaria.

Sponges are found in many habitats, not just those dominated by laminar flow and high currents. In fact, sponges are found in just about all possible combinations of water currents and flow types, from high current areas in surge or highly turbulent areas to extremely calm waters. Sponges from many of these types of areas may do quite well in aquaria. Unfortunately, such sponges tend to mold their shapes to the currents and substrata surrounding them. In other words, the same species will have differing appearances in differing habitats. In the most extreme examples of this environmental sculpting of shape, many sponges change form and appearance as they grow, responding to changes in the water currents generated by either their own shapes or by nearby shapes in the environment. Such sponges have a labile shape and are damnably difficult to identify; about the only way of ensuring a proper identification is by comparing a microscopic examination of the sponge's spicules to what is known from the technical literature of the sponges from a given area. For such a process to work several different things must occur.

• First, the area of the sponge's origin must be known.

• Second, the aquarist has to have access to, and know how to properly use, a microscope.

• Finally, the aquarist has to have access to the technical literature describing the sponges by spicular type.

The odds of satisfying all of these requirements are slim to none for most hobbyists and, because of that, many of the common demosponges in their tanks cannot be identified with any degree of certainty. This results in an interesting paradox; the sponges that they can identify by comparison to photographs are ones that generally can't be kept, and the sponges that generally do well in tanks are not easily identified.

At this point, I should probably discuss a small group of sponges called "Sclerosponges." These animals secrete siliceous spicules imbedded in a calcareous matrix, and the living cells form a layer upon and covering this stony matrix, much like tissue frosting on a calcareous cake. Sclerosponges are somewhat uncommon, but are generally found living on coral reefs. They were first discovered living in caves, which is one of their preferred habitats. Although unlikely, it is possible that they have been collected incidentally for the reef hobby. The only way these sponges can be identified is by examining the rocky matrix underlying the tissue frosting to find the silica spicules it contains. Superficially, they appear to be a thin layer of sponge living on rock; however, in this case, they actually secrete the "rock." For a few years, from about 1970 to about 1985, many authorities considered them in a separate class, but a lot of research has showed that the "Class Sclerospongia or Stromatoporoidea" is an artificial grouping of several superficially similar sponges from several demosponge subgroups. Basically, this "grouping" is a good example of convergent evolution at work.

Figure 6. A sponge that is possibly a sclerosponge photographed on the roof of a cave in a Caribbean reef. The surface's "star-like" or "stellate" pattern is characteristic of some sclerosponges, but the sponge's identity must remain uncertain, as the specimen was not collected for definitive identification. The field of view is about 5 cm (2 inches) across.

Step 2b. Identification of Calcareous Sponges

Compared to demosponges, the calcareous sponges are significantly less diverse, and the ones typically found in aquaria are relatively easy to name. Whether or not that name is a "real" one, well, that is open to question. Calcareous sponges are generally small; although some species get quite large in nature, colonies in aquaria that are an inch in size are giants. In natural environments, larger species may be relatively common, but such species are not often found in aquaria. The typical aquarium example is cylindrical or tubular, and while other colors are found in nature, aquarium species are almost uniformly white, tan or a drab, nondescript gray.

Probably the type of calcareous sponge most likely found in reef aquaria are the so-called "Pineapple" sponges. These small, white or gray sponges often appear in a reef aquarium a few weeks or months after it is set up, and may or may not persist for a long time. They tend to appear in areas of relatively high current flow, and big ones reach heights of an inch or so. Aquarists commonly say that they are in the genus Scypha. This may be true, but see the discussion and example in the next couple of paragraphs for the problem: calcareous sponges of essentially the same shape, size and color are described from different areas under the generic names of Scypha, Grantia, Sycon, Leucilla and Leucandra. Species from these species cannot be distinguished by cursory examination. Snap "off-the-wall" identification by aquarists is particularly problematic with the calcareous sponges, which tend to be smaller and more symmetrical than most other sponges.

A Few Words of Caution

Even within a group that has consistent structures and shapes, the identification of sponges is not an easy task. For example, not only do some species of calcareous sponges in the genera Scypha, Grantia, Sycon, Leucilla and Leucandra look alike, small individuals of species from the other classes of sponges can have the same shapes, colors and symmetry. The ONLY way to really tell all of these animals apart is by microscopic examination of spicular patterns and abundances. Nevertheless, some aquarist literature references and other "experts" claim to be able to tell these various species apart using only pictures or simple verbal descriptions. This is simply not possible.

To illustrate some of the difficulties of sponge identification even within a group of "well-characterized" and "well-known" species, I have included the following portion, called a couplet, of a taxonomic reference specifying the differences between two calcareous sponge species. Several choices precede this choice, basically determining that the body is wrinkled, flattened and sac-like.

Choice 1:

Height typically 2-3 cm, width 1-2 cm; with a very short fringe of oxeas around the osculum; oxeas 150-500µm, triact rays 40-150 µm, short tetract ray 50-60 µm, long tetract rays 60-90 µm...

Grantia ? compressa

Choice 2:

Height typically 6-16 cm, width 2-5 cm; without an evident fringe of oxeas around the osculum; oxeas 400-500µm, triact rays 120-350 µm, short tetract ray 40 µm, long tetract rays 150 µm...

Leucandra similar to levis

The distinction between these species is pretty clear, provided that you can determine which spicules are called oxeas, triacts and tetracts, as well as being able to measure them. To use this couplet of descriptions, you need a compound microscope. Additionally, although using this couplet to identify the sponges seems to be straightforward, notice the many places where the characteristics overlap - and these are not closely related animals! Secondly, note that when finished, both choices lead to incompletely described species. This faunal key (Kozloff, 1996) was published in 1996 and covers one of the world's better-known marine faunas - and yet it is still impossible to definitely identify some common sponges. The sponge fauna of most tropical marine areas is poorly characterized and described... and yet we have people foolishly purporting to be able to identify sponges by pictures alone.

Aquarium Husbandry

I suppose that after "What is it?," the next question most aquarists ask is, "How do I keep it?" Unfortunately, for this group, as well as for other diverse animal groups, there is no simple good answer. There are well over 5,000 species of sponges, and as with all other animal groups, each species is adapted for its own particular set of conditions. There simply is no "one size fits all" answer. Unfortunately, most aquarists keep trying to prove that there is. A lot of animals get killed in such endeavors.

To keep any animal in good health, it must be kept under the environmental conditions in which it does best. In the case of reef sponges, probably all of them will thrive under the salinity and temperature conditions of the average tropical coral reef; in other words, a temperature around 82°F, with a salinity of 36 psu. Such conditions are easy to duplicate in aquaria. And they are a good first step.

But they are only a first step.

The primary environmental condition that will determine the survival of any sponge is the water flow regime. To understand why water conditions are important, it is necessary to review how sponges gain nutrition. In general, sponges fill a volume with "tissue" and pump water through that volume to extract usable particulate food. A simple tubular or cylindrical sponge with its food collection area on the inner surface of a large cavity "wastes" a lot of internal space. Some of this is "dead" space caused by water currents, other space is wasted when water currents carry the suspended particulate material too far from the choanocytes. Consequently, most sponges' filtration area has been maximized by filling the cavity with - dare I say it? - a "spongy" mass of small chambers, each lined by choanocytes. Large sponges may have more than 10,000 chambers/mm3 (164 million chambers/cubic inch) containing, in total, many billions of choanocytes. Some of these large sponges have been calculated to pump their own weight of water through themselves about every five seconds. The larger ones likely can filter several thousand liters per day, removing up to 95% of bacteria and particulate organic material from the water. These sponges also differ from the "basic" sponge described in last month's article in that their body is often asymmetrical and without ostia; the visible pores on the outer surface are the openings of the water channel system (Reiswig, 1975; Ruppert, et al., 2003).

As a general rule, sponges feed primarily on very small particulate organic material of the size category containing bacterioplankton and the smallest phytoplankton. Larger phytoplankton also may be eaten, but this material is generally not collected by the choanocytes, but rather by the cell's surfaces around the small incurrent water passages. Many tropical sponges supplement their filter-feeding by having a symbiotic relationship with zooxanthellae. Regardless of this symbiosis, all sponges need to feed. They absorb dissolved organic material from the water, but also need to have a source of bacterial or nanoplankton. This source may be maintained in aquaria by having a good sand bed with sufficient infauna to cause some rapid turnover in bacterial productivity. Sponges will compete with other bacteriovores such as tunicates and, potentially, some SPS corals for this resource. Supplementation of the system with small, less than 5µm in diameter, phytoplankton cells may provide additional nutrition. Interestingly, a few sponges that are apparently wholly carnivorous in the family Cladorhizidae, catching prey by the action of hooked spicules on their body's surface, have recently been described from caves in the Mediterranean and deep seas elsewhere (Vaceletand Boury-Esnault 1995). These animals, not found in aquaria, eat small crustaceans.

Sponge Natural History Considerations for Aquarists

In nature, space often is a limiting resource for marine filter-feeders. Given that sponges sit in one place and filter water, they must have some way of maintaining their environmental space or they would be quickly overgrown or killed. As it turns out, sponges are masters of chemical warfare. Some of their chemicals are potent, and not only to marine animals. Several tropical sponges are toxic or irritating to the touch to humans (Humann, 1992). Nevertheless, a sponge's chemical warfare capabilities are not intentionally directed against humans; rather, these exceptionally toxic chemicals are meant to be effective against predators or potential competitors for space such as corals (Porter and Targett, 1988). Because of the toxic array of chemicals they contain, relatively few animal groups have members that eat sponges. Some of these are the snails such as dorid nudibranchs, a few sea stars and a few fishes (Mauzey, et al., 1968; Bloom, 1981; Pawlik et al, 1995; Wulff, 1995). These predators often metabolically modify sponge's chemicals for their own defense. Both the sponges and their predators may at times liberate copious quantities of chemically-laden mucus. In natural situations, this chemical soup would deter predators or competitors and then disperse. In the closed environment of a reef aquarium, the chemicals are contained and may be toxic to many aquarium animals. Many of these poison factories are brightly colored, presumably to alert potential predators of their presence. Humans tend to view these colors as pleasing and attractive, a rather perverse twist on their presumed purpose. Consequently, few attractive sponges or their predators are good candidates for inclusion into a closed reef aquarium system. Aquarists need to remember that sponges are not passive lumps of tissue. They continuously fight for space; even if, in your opinion, they don't need to. In this ongoing struggle, they can and will produce very nasty substances that can affect other animals, and one can almost never be sure which ones will be affected and which ones will not. On the flip side of this record (does anybody still remember records, and flip sides?), Halichondria moorei, for example, has long been used by New Zealand natives to aid healing. Nearly 10% of the sponge's weight is composed of the potent anti-inflammatory drug, potassium fluorosilicate. Unfortunately, the sponges found in aquaria are more likely to cause inflammation rather than heal it.

Some other sponges are not necessarily the best of reef tank inhabitants for another reason. These sponges, the clionids, are typically yellow or reddish sponges that are specialized to live inside calcareous substrates. In aquaria and on reefs, that means they erode corals away from the inside out. These are very important bioerosive organisms on reefs, and often what appears to be large "solid" coral heads consist of nothing more than a veneer of coral tissue and a thin calcareous layer over a wholly or partially eroded coral skeleton that has been replaced by the sponge. In some aquaria, they have become somewhat of a problem.

Some sponges may easily be kept in reef and fresh-water aquaria, if a few precautions are followed. As a general rule, most sponges should never be exposed to air. Many shallow water sponges produce copious amounts of mucus, and this mucus can form a protective layer if the sponge is exposed to air. These species are not affected at all by even prolonged exposure to air. Many moderate to deep water sponges, however, often lack such a mucous coat, and if they are exposed to air, even briefly, many of the very small passages in their water system become filled with air and are effectively plugged. The animal has no way to clear this air from its tiny tubules and cells adjacent to air die, decompose and produce gases which plug other tubes. This effect cascades and the sponge dies. These animals are never naturally exposed to air or bubbles, and air is deadly to them. As aquarists seldom know where their sponges originate, it is prudent not to cause problems by carelessly handling the animals at the air/water interface. Additionally, it is necessary to be aware of the reef aquarium's water conditions. If the water has been treated to remove silica, most sponges will not grow well as they require silica for their spicules. Calcareous sponges will do all right under those conditions, but remember that, like corals, they depend on the amount of calcium in the water. They also compete with the corals for calcium, so you need to monitor the calcium levels closely if heavy sponge growth is present.

Sponges often enter aquarium systems as incidental, and often unnoticed, hitchhikers on live rock. If they grow and start to spread, and you don't notice a concurrent decline in your other animals, then you know 1) that you can keep some sponges, and 2) the ones you have are relatively benign. Alternatively, if you purchase a sponge, try to get one that has been maintained in your dealer's tank for a while. Dying sponges generally become obvious in a hurry, so if the sponge has survived for a week or two, it may be okay. Sponges that can injure people are unlikely to show up at dealers; however, it occasionally happens. Ask the dealer if he has ever had a "reaction" to the sponge. If the sponge has been kept in a tank with other inhabitants, try to determine if those animals seem to have reacted to the sponge. Once the sponge has been placed in the home aquarium, monitor its condition carefully. If it starts to develop a gray or white film growing over it, it has started to die. Most sponges that have this film will not recover. If you wish to try to keep the animal alive, transfer it to a separate tank so that it will not foul your main system's water.

Many tropical sponges have photosynthetic symbiotic algae of a couple of types. These may be dinoflagellates similar, but not identical, to those found in corals. Additionally, many sponges also harbor symbiotic cyanobacteria and, actually, quite an array of other bacteria; in some species, the bacteria may account for as much as 40% of the weight of the sponge. The sponge/bacteria symbioses are particularly important in many tropical sponges - and presumably temperate ones as well - but they just haven't been investigated there. The symbiotic algae go a long way to providing enough sugars to fuel the sponge's metabolism, often providing a competitive edge for these sponges on a reef. Some of these species, as might be expected, do well in reef aquaria, but some sponges harboring similar species of zooxanthellae also do very well in the deep cold water of Antarctica. One of these sponges, Rossella racovitzae, has long (10 cm!) ossicles that act as fiber optic light pipes to direct light down to the zooxanthellae that live below the water sediment interface in the mud (Cattaneo-Vietti, 1996).

Figure 10. Some hitchhiking sponges can become pests. This calcareous sponge, similar to a species of Leucosolenia, was sent to me by a hobbyist for identification. The sponge has effectively taken over most of the rock surface in this tank and has proven essentially impossible to eradicate. Even with a specimen and microscopic analysis, I could not identify this species, as I did not know where the sponge originated.

If the animal seems to shrink or otherwise deteriorate, move it. Some of the variables to consider with sponges are light intensity (most species don't like really bright light - but a few do), currents (many species like strong currents), potential competitors (don't place it too close to either hard or soft corals; they fight with chemicals, too) and potential predators in your tank (keyhole limpets and angelfishes will graze on some sponges). Once you have found a good spot and your sponge is growing well, you will have a beautiful and interesting addition to your system.

References Cited:

Anderson, E. S. 1971. The association of the nudibranch Rostanga pulchra MacFarland, 1905, with the sponge Ophlitaspongia pennata, Esperiopsis originalis, and Plocamia karykina. Doctoral Thesis, Biology, University of California, Santa Cruz. 151 pp.

Bakus, G. J. 1966. Marine poeciloscleridan sponges of the San Juan Archipelago, Washington. Journal of Zoology, London. 149:414-531.

Bloom, S. A. 1981. Specialization and noncompetitive resource partitioning among sponge-eating dorid nudibranchs. Oecologia. 49:305-315.

Cattaneo-Vietti, R., G. Bavestrello, C. Cerrano, M. Sar, U. Benatti, M. Glovine and E. Gaino. 1996. Optical fibres in an Antarctic Sponge. Nature. 383:397-398.

Humann, P. 1992. Reef Creature Identification. Florida Caribbean Bahamas. New World Publications, Inc. Jacksonville, Florida. 344 pp.

Kozloff, E. N. 1996. Marine Invertebrates of the Pacific Northwest. 1st pbk. ed., with additions and corrections. University of Washington Press. Seattle. 539 pp.

Lambe, L. M. 1893. Sponges from the Pacific Coast of Canada. Proceedings of the Transactions of the Royal Society of Canada. 11:25-43.

Mauzey, K. P., C. Birkeland and P. K. Dayton. 1968. Feeding behavior of asteroids and escape responses of their prey in the Puget Sound region. Ecology. 49:603-619.

Pawlik, J. R., B. Chanas, R. J. Toonen & W. Fenical. 1995. Defenses of Caribbean sponges against predatory reef fish. 1. Chemical deterrency.

Porter, J. W. and N. M. Targett. 1988. Allelochemical interactions between sponges and corals. Biological Bulletin. 175:230-239.

Ruppert, E. E, R. S. Fox, and R. D. Barnes. 2003. Invertebrate Zoology, A Functional Evolutionary Approach. 7^th Ed. Brooks/Cole-Thomson Learning. Belmont, CA. xvii +963 pp.+ I1-I 26pp.

Vacelet, J. and N. Boury-Esnault. 1995. Carnivorous sponges. Nature. 373: 333-335.

Wulff, J. L. 1995. Sponge-feeding by the Caribbean starfish Oreaster reticulatus. Marine Biology (Berlin). 123:313-325.