Porifera Life Cycle

The life cycle of a sponge is a relatively simple one. Sponges can reproduce sexually and asexually. There are many sponge species in which each sponge is considered male and female. When it comes to sexual reproduction, a sponge can play either role. The male sponge releases sperm into the water which travels towards and enters the female sponge. After fertilization occurs, a larvae is released from the female sponge into the water. The larvae floats around for several days until it can find a suitable substrate to stick to. At this point, the larvae will begin to grow into an adult sponge. Sponges become more diverse when different sponge species reproduce with one another (Myers, 2001). The sexual life cycle is depicted below in Figure 1.

When sponges go through asexual reproduction, it is by a system called budding. This occurs when a small piece of the sponge is broken off and is able to grow into a whole new sponge. Like in sexual reproduction, this small piece of the sponge must find a substrate to cling to in order to grow into an adult sponge (Myers, 2001).

 

 

 

Sponges and their Associations with Other Organisms

Sponges make up an important component of coral reefs and filter the surrounding water and cycle nutrients (Hultgren, 2014). Sponges have a wide range of associations with other organisms, which can include facilitating primary production, providing a habitat for another organism, or even providing protection to organisms from predation. Sponges interact with a wide range of organisms, so it is sometimes difficult to understand the role sponges play in these relationships (Bell, 2008).

To facilitate primary production, sponges associate themselves with photosynthetic organisms. A review paper by Bell (2008) mentions that these photosynthetic relationships contribute between 48 and 80% of the sponge’s energy requirements and around 10% of the reef’s productivity. This paper also mentions that the role of sponges as primary producers may only be important for nutrient-poor waters, such as those found in the tropics. Sponges are also involved in secondary production because other organisms such as fish, crustaceans, and molluscs consume them. These predators vary over the differing ecosystems that sponges are found in (tropical, temperate, polar, etc.). Since sponges harbor photosynthetic organisms, the sponges being eaten by predators could be seen as a herbivorous interaction because the photosynthetic organisms may be of greater nutritional value than the actual sponge itself (Bell, 2008).

Sponges also provide microhabitats for smaller species. Costs and benefits to each organism in the relationship are not well studied. In an experiment by Hultgren (2014), the relationship between the Synalpheus species of snapping shrimp and the marine sponges they inhabit. It was found that the shrimp had varying effects on the sponges. When predators were present, the shrimp had positive effects on the sponges and negative effects during periods when the sponge was actively growing. These negative effects were likely the shrimp consuming the sponge as it grew. This study suggested a future study in which abiotic and biotic stressors should be manipulated to see if the relationship between shrimp and sponge changes. Sponges also interact with other organisms such as bivalves. When bivalves had sponges living on their valves, their risk of predation by starfish was reduced. The sponges benefit from the association by having an increased feeding efficiency. Sponges are also associated with crabs, which have been observed to use the sponges to cover their bodies as a form of camouflage (Bell, 2008).

 

Where Can Poriferans be Found?

Sponges have a global distribution that encompasses polar and tropical latitudes alike.  They can be found from deep depths in the ocean to shallow rock pools.  Poriferans have been known to occupy habitats that include marine thermal vents as well as freezing arctic waters.  While many may associate sponges with a solely marine habitat, a portion of the phylum occupies freshwater as well such as the preserved specimen pictured below, found near a hatchery in New York.  These freshwater sponges are represented by 219 out of the 15,000 species of Poriferans, all belonging to the suborder Spongillina of the class Demospongiae.  While the diversity of freshwater sponges may be limited in comparison to their marine relatives, their abundance within their freshwater habitats is often greater.  What is most amazing about freshwater sponge diversity is the specificity of the taxa found occupying a body of water.  Around 47% of freshwater sponges originated from the body of water they inhabit, and new species discoveries can often been associated with new genre as well (Manconi and Bronzanto, 2008).

As mentioned earlier, sponge fossils have been found dating back to the Precambrian, where poriferan remnants have been identified in marine strata (Porifera: Fossil Record, 2006).  Colonization of freshwater by sponges has been dated back to the Mesozoic period, which occurred some 220 million years ago.  This theoretical date is based off of structures found in the oldest known freshwater sponge fossils, called gemmae.  These are highly conserved features within Spongellina, and act as asexual propagules of the sponge which can become dormant if environmental conditions are not favorable.  This is a feature that has been associated with the ability of sponges to occupy some of the unique inland habitats they are found in (Manconi and Bronzanto, 2008).  Until relatively recently in Earth’s geological time scale, sponges have constituted a large part of the framework of oceanic reefs.  Today, sponges still remain an important part of reef communities, however do not contribute nearly as much to mass as corals (Porifera: Fossil Record, 2006).

 

Diversity in Sponges

There are many times when it is difficult to differentiate between two sponge species. On more than one occasion, two sponge species were thought to be one until scientists took their observations of the sponges one step further and realized that there was a difference between the two. There are various ways in which sponge species can be distinguished from one another. Some are seen as a food source to certain animal species while other very similar sponges are not, such as seen in fire sponges (Tedania ignis) and volcano sponges (Tedania klausi). These two sponge species used to be seen as one diverse species, fire sponges, until scientists performed feeding choice experiments as well as a morphological and molecular study and determined that they were not the same species at all. Volcano sponges are eaten by sea stars, while fire sponges are not, leaving the species to live in very different habitats. These two species were also found to have a difference in their susceptibility to disease and ability to withstand a wide change in temperature and salinity. Molecular markers also helped scientists to see the difference between the sponge species Scopalina blanensis and Scopalina lophyropoda. S. blanensis responds positively to seasonal environmental changes in temperature and food availability, while S. lophyropoda responds similarly throughout these environmental changes (Wulff, 2012).

Differences in sponge species can be seen in many different aspects of the sponge and its life. They can be based upon the role that a sponge takes in its community, their association with other species, morphological (physical) characteristics, and their vulnerability to hazards. An example of the morphological differences between sponges can be seen below in Figures 3 and 4. Some of these contrasting features can be determined through observation, while others require the use of experiments (Wulff, 2012).

 

Figures 3 and 4. The physical diversity of sponges is clearly seen between these two dried marine sponge specimens. Pictures taken by Christine Koporc at the OSU Museum of Biological Diversity.

 

 

Freshwater and Saltwater Sponges

Sponges live in a wide variety of ecosystems. Sponges are such simple organisms that they have been able to adapt to many different environments, which is why they are able to be found in nearly every type of body of water. They are found in the deep sea, in coral reefs, near hydrothermal vents (which are 3,000 to 7,000 feet below the water’s surface), and in various freshwater environments (Masters, n.d.). While most live in marine environments, such as oceans, there are still some that live in freshwater environments, such as lakes, ponds, and streams. Around 200 of the 15,000 known species of sponges live in freshwater environments (Skelton & Strand, 2012). The important functions of marine sponges have been determined by their impact on substrate (reef creation and erosion of hard oceanic substrate), their coupling with other organisms living at the bottom of the sea (their role in the carbon cycle, silicon cycle, nitrogen cycle, and oxygen depletion), and their interactions with other organisms (Bell, 2008). Much less is known about freshwater sponges and the roles that they play in their ecosystems, though it is believed that their roles will be very similar to those that are seen in marine sponges (Skelton & Strand, 2012). Even with this limited amount of information for their functional roles, freshwater sponges are found to be very hardy creatures that can withstand a wide variety of situations, such as drought, chemical pollution, and fluctuations in water flow, pH, and temperature (Masters, n.d.).

 

How sponges are used today

Sea sponges have vast economic importance. The types used are mainly demospongiae because they possess spongin which is the flexible skeleton like structure of the sponge.

Video 1. Student demonstrates the flexibility of the spongin using a dissecting microscope.

 

The most popular sponge used is the Wool sponge; it is the softest and most durable sponge. Firstly, they are used in industry. There is a city in Florida called Tarpon Springs located in the Gulf that is the acclaimed Sponge Capital of the World. They harvest and export a majority of the worlds sponges. Before World War II, Florida produced 600,000 pounds that is 7,800,000 individual sponges on average for human use. In recent years they produce around 70,000 pounds, that is 910,000 individual sponges on average (Stevely & Sweat, 2015).

Sea sponges are very popular in the health and beauty field. They can be used for cleaning an array of surfaces and have better water retention than that of the artificial sponge. Most popular uses include car care, household cleaning, makeup application and removal, skin exfoliant for when bathing, and personal care. If taken care of properly, they can last years on end where an artificial sponge can fall apart and be riddled with bacteria after months of use.

Other organisms use sponges

Dolphins will use marine sponge to protect themselves while searching for food. They will grab a sponge from the seafloor and fit it around their beak to protect it from chunks of coral or rock that could hurt them. It is hypothesized that they hunt the bottom dwelling fish instead of the ones out in the open ocean because the bottom dwelling fish are more nutritious (Morell, 2011). Also, a variety of microorganisms, worms, crabs and shrimp will inhabit the cavities in the sponges. Sponges also serve as a protection mechanism for scallops. The sponges will attach and live on the shell and protect it from organisms such as starfish which can damage it (Bean-Mellinger, 2015).

Human Impact

Sponges have been harvested since the 1800’s because they are beneficial and durable for many uses. They are a huge industry in Florida. The regeneration of the sponges that are harvested is important for the health of the ecosystem; there are now certain parts of Florida where harvesting sponges is illegal. In the beginning sponges were harvested using the hook method. This entails a diver using a pronged hook to grab the sponge then rip it free of its base. It was later discovered that the hook method inhibits the chance of that sponge fully regenerating. It is now a law that sponges have to be harvested using the cutting method, making sure to leave enough left at the base of the sponge for proper re-growth. This entails using a knife to cleanly cut the sponge away. Doing this brings the chance of survival for the sponge to 71% versus 41% for hooked ones (Stevely & Sweat, 2015).

Conclusion

It’s now easy to see why we can appreciate phylum porifera and its place in basal Metazoa.  What may represent one of the first multicellular organisms that successfully survived and diversified to current day is also a reminder of Metazoa’s more humble beginnings in evolutionary history.  While these hermaphroditic organisms may not have organized tissue, they certainly have specialized cells and organelles to carry out the functions that would otherwise be performed by more complex structures in higher animals. Though their mobility is limited to larval stages, gametes, and the occasional passive gemmae in freshwater specimens, these organisms have also managed to occupy an incredible diversity of habitats, all at varying depths, latitudes and longitudes.

Sponges have had a large impact on their environment as well.  This includes not only their primary role in reef structure throughout geological history, but direct use by other animals.  Animals like humans, who rely on marine sponges in particular as an industry, can also have a significant influence on their survival through overharvesting.  Poriferans are certainly amazing creatures, and their ancient lineage in conjunction with their diversity in taxa, habitat, chemical production, and ecological utility represent the merit in appreciation of these organisms.

 

 

Literature cited

Bean-Mellinger, B. (2015). Relationship Between Scallops and Sponges. Animals. Retrieved from http://animals.pawnation.com/relationship-between-scallops-sponges-9329.html.

Bell, J. J. (2008). The Functional Roles of Marine Sponges. Estaurine, Coastal and Shelf Science, 79(3), 341–353.

Hultgren, K.M. (2014). Variable effects of symbiotic snapping shrimps on their sponge hosts. Marine Biology 161, 1217-1227.

Manconi, R., Masters, R. (2008). Global Diversity of Sponges (Porifera: Spongillina) in freshwater. Hydrobiologia, 595(1), 27-33.

Masters, M. (n.d.). Habitats of Sea Sponges. Retrieved from http://animals.pawnation.com/habitats-sea-sponges-2396.html.

Morell, V. (2011, July). Why Dolphins Wear Sponges. Science. Retrieved from http://news.sciencemag.org/environment/2011/07/why-dolphins-wear-sponges.

Myers, P. (2001). Porifera Sponges. Retrieved from http://animaldiversity.org/accounts/Porifera/.

Porifera: Fossil Record. (2006). Retrieved March 28, 2015, from http://www.ucmp.berkeley.edu/porifera/poriferasy.html.

Skelton, J., & Strand, M. (2012). Trophic ecology of a freshwater sponge (Spongilla lacustris) revealed by stable isotope analysis. Hydrobiologia, 709(1).

Stevely, J., & Sweat, D. (2015). Florida’s Marine Sponges: Exploring the Potential and Protecting the Resource. Retrieved March 28, 2015, from http://edis.ifas.ufl.edu/sg095.

Wulff, J. (2012). Ecological Interactions and the Distribution, Abundance, and Diversity of Sponges. In Advances in Marine Biology (pp. 273–344).

 

An Introduction to the Sponges

Many of us may find it easy to appreciate the diversity of animals that inhabit our planet. Whether it be a bird, insect, or mammal, we humans are often drawn towards some sort of fascination of their mere existence. But what preceded all of the animals we see around us? What may come to mind are images of dinosaur, trilobite or coral fossils, but there existed animals much less complex than any of these. Porifera, or sponges, represent some of the most primeval of animals, lacking body symmetry or specialized organs.  Instead, their body consists of specialized, individual cells that serve different functions for these filter-feeding, sedentary organisms (Blair, 2009). Sponges can be found worldwide, from shallow reefs to deep ocean trenches. They inhabit both marine and freshwater environments, and come in a variety of shapes and sizes. If these organisms represent such ‘ancient’ animals, how old are they? The oldest reliable sponge fossils date back 535 million years ago from Northern Iran (Antcliffe et al, 2014). In addition, sponges are thought to have diverged from the animal phylogeny during the Precambrian, which lasted up until 540 million years ago (Antcliffe et al, 2014). Their basal status in Metazoa, or animals, and ancient lineage represent just a portion of the significance of these bizarre organisms.

Porifera Phylogeny

The group of organisms known as sponges (Porifera) is considered the earliest branching group of Metazoans, or animals, with fossils described from the Vendian Period, dating back 650-543 million years ago (Porifera: Systematics, 2006). Phylogeny in this phylum, or group of organisms, is an ongoing debate, with the current consensus viewing sponges as possibly mono- or paraphyletic (Blair, 2009). Monophyly would indicate a recent common ancestor of all sponges, while paraphyly would indicate that the group of organisms we regard as sponges is actually made up of groups that developed separately over a relatively extensive time. The sponge phylum consists of four currently recognized classes; the Hexactinellidae, Demospongiae, Calcarea and Homoscleromorpha. The relationship between these four classes is still unresolved (Wörheide et al, 2012). Gross morphology suggests the clade is monophyletic.  With the advent of molecular systematics, this monophyly was put into question; however, after extensive sampling and inclusion of specimens from all classes, one recent paper suggests monophyly may be the agreed relationship (Wörheide et al, 2012). Regardless, Hexactinellida and Demospongia are both regarded as being monophyletic, representing those sponges which contain silica-based skeletons (Blair, 2009).

One of the main diagnostic features of sponges had previously been their spicules, which constitute the hard support structure of these organisms. This was later proven to be an inaccurate means of identification, as currently existing sponges have been discovered with solid calcium-based skeletons, matching some features observed in the fossil record (Porifera: Systematics, 2006). Phylogenetic analysis of Porifera is conducted using mitochondrial DNA sequences, in conjunction with analyses of morphological features as well (Wörheide et al, 2012). Porifera are not just significant for their roles in ecology, pharmaceuticals, and commercial products but also in developing hypotheses of what the last common ancestor of all animals could have been.

 

Two proposed models for Porifera phylogeny.  Hex= Hexactinellida, Demo= Demospongia, Cal= Calcarea, and Homo= Homoscleromorpha.  In the left tree, Homoscleromorpha and Calcarea are more closely related to the rest of Metazoa than the other two sponge classes.  In the right tree, all classes share a common ancestor. (Adapted from Wörheide et al, 2012, by Dylan Sedmak)

Fossil Record

          Porifera are the first animals on the metazoan phylogeny, having diverged from choanoflagellates 1020 million years ago (mya). The sponge group Hexactinellida diverged from the Demospongia group around 750 mya and it is estimated that the Calcarea group later diverged from the other two groups an estimated 754 mya (Sperling, et al., 2010). Porifera are the most primitive of animals and thus have an early branch on the animal phylogenetic tree, so they’re likely candidates for Precambrian ancestry (Gehling & Rigby, 1996). To understand this, one needs to look at two sponge groups: the Hexactinellids and the Demosponges. These are the two oldest sponge groups, and both have siliceous spicules. Sperling, et al., (2010) suggests that these spicules must have evolved before the common ancestor of Hexactinellids and Demosponges, which means that these spicules were present in the Precambrian, but not fossilized.

Sponges have a fossil record that extends back further than 500 million years. The oldest fossil found for Hexactinellids are siliceous spicules that were found in Northern Iran and date back to approximately 535 mya and the earliest fossil found for Demosponges came out of Siberia and was dated to be 523.5-525.5 mya (Antcliffe, et al., 2014). These fossil remains appear to be dated around the Precambrian-Cambrian boundary, which is associated with great diversification of animals. Finding fossils for the Calcarea sponges is very difficult because they are not as diverse as the other two groups and they lack siliceous spicules which makes it difficult to find preserved specimens (Antcliffe, et al., 2014).

Finding these fossils and correctly identifying them as sponges is a difficult task, as most reported sponge fossils tend to be volcanic shards or inorganic crystals (Gehling & Rigby, 1996). One paper by Antcliffe, et al., (2014) discusses 20 potential candidates for being the oldest Porifera fossil found. This paper also discussed how it can be difficult to define the criteria that determines the oldest fossil because there is no substantial studies done on the formation of cells that make up sponges. There are no studies that study fossilized sponge spicules that look like today’s sponges or vise versa – looking at potential spicules that look nothing like spicules we find today. Antcliffe, et al. (2014) also made the point that these potential fossils may be misinterpreted as individuals rather than part of a larger organism, which further complicates the fossil record.

Finding just the fossilized spicules makes it difficult for scientists to get a clear picture of the shape and form these sponges took. Sponge fossils found in Australia that date back to the Ediacaran period (Precambrian) give some insight into what these first sponges must have looked like. Gehling and Rigby (1996) found that these fossils were formed in hypo-relief on sandstones, with external molds of fossils commonly found. These fossils indicate that the sponges were dome shaped with an osculum at the apex. Since there are no siliceous spicules that have been found before the Precambrian-Cambrian boundary, Gehling and Rigby (1996) note that the siliceous spicules would not be expected to survive longer than the organism’s tissue during fossilization due to being preserved in sandstone substrate.

 

Molecular Clock

        The molecular clock for Porifera suggests that their origin was prior to the Cambrian explosion. This fits with the assumptions made by Sperling, et al. (2010) that based on the siliceous spicule fossils of Hexactinellids and Demosponges, these spicules must have evolved prior to the Cambrian explosion. Though this indicates a gap in the fossil record, molecular clock analyses can still be done to determine divergence time estimates.

          A paper by Antcliffe, et al., (2014) discussed how it is sometimes difficult to get accurate divergence times because fossils are needed to help the molecular clock to be more accurate in its predictions. The dates of the fossils help the clock analyses to better date divergence times. These dates were found using a small number of nuclear housekeeping genes, which are genes that are generally used to date animal phylogenies. This paper found that the housekeeping genes indicated Porifera diverged from the animal lineage around 800 mya in the Precambrian.

Another paper by Sperling, et al. (2010) did two sets of molecular analyses. One set was with multiple sponges from Hexactinellida and Demosponges. The second set was done without Hexactinellida because the Hexactinellid group is the first group that diverged from the metazoan lineage. Their analyses led to the conclusion that the Silicea (both Hexactinellids and Demosponges) originated around 759 mya and also Demosponges greatly diverged within its own clade around 699 mya. For more divergence dates in the Poriferan phylogeny, refer to Figure 2.

Figure 2. This timeline represents the estimated divergence times of the Porifera clade. Data represented in this timeline comes from class notes, Sperling, et al. (2010) and Antcliffe et al. (2014). Porifera diverged from the animal (Eumetazoan) lineage approx. 800 mya with Demosponges and Hexactinellids diverging 759 mya and Calcareans diverging 754 mya. Demosponges further diversified into its own clade 699 mya and Calcareans also further diversified 488 mya. Hex. = Hexactinellids, Demo. = Demosponges, Cal. = Calcareans. Phylogeny created by Sarah Petersen.

 

Key evolutionary innovations

Slime

Some sponges are able to produce slime as a defense against debris or other marine organisms. The amount of slime a sponge can make depends on the type of sponge. There are sponges that have absolutely no slime at all, while others only produce a little and others can produce a lot (Ackers, Moss, & Picton, 1992). The slime certain sponges produce is actually toxic. This natural defense comes from metabolic waste produced by the actual sponge or from toxins that the sponge has modified from these original chemicals (Goudie, Norman, & Finn, 2013).

Figure 3. In this image, a student is seen displaying the sponge’s natural slime excretions in a laboratory setting. Picture taken by Natalie Iannelli.

 

Spicules

Spicules are part of the sponge’s “skeleton” and help to give it shape. There are a wide variety of spicules that can be seen in varying sponges. They can help us determine when different sponge species evolved because of their ability to be genetically determined. The environment can also cause spicules to develop in different shapes or sizes and for more than one type of spicule to be present at a time. Spicules are thought to help sponge in a variety of other ways, such as by helping sponge larvae maintain buoyancy, allowing the larvae to reach a spot to settle, enhancing reproductive success, and catching prey (Uriz, Turon, Becerro, & Agell, 2003).

Figure 4. A microscopic view of a sponge slurry; the spicules can be observed. The view is on a compound microscope at 400X magnification. Picture taken by Christine Koporc and Sarah Petersen.

 

Toxins

Sponges are able to reuse toxins from other organisms around them, though they can also create their own toxins or in collaboration with the microbes that live inside of them. Many sponges have been found to release highly toxic chemicals and these excretions make up some of the most toxic chemicals in nature. Many of these toxins are used to protect themselves against predators or to outcompete other organisms in a crowded area, but they can be used by humans as well. It has been determined that some of these chemicals could be used in anti-cancer, anti-malaria, and pain control applications (Queensland Museum, 2012).

Apoptosis

Cell death, or apoptosis, is when a cell determines that it is no longer needed and it uses an intracellular death program to get rid of the excess cells. This is a common occurrence in organisms and it even takes place in healthy humans. For example, in a normal healthy human, billions of bone marrow and intestine cells die every hour. There are various reasons for this phenomenon, some of which are in order to properly form a structure when an organism is an embryo or to help ensure that the number of cells does not become too large (Alberts, et al., 2002). Apoptosis first developed in the transition between sponges and their ancestor, meaning that sponges were the first organisms to have a trait of this sort (Werner & Muller, 2003).

Water flow

Sponges contain holes in their bodies to maximize efficiency of water flow. The more surface area there is to absorb nutrients it gets from the water, the better off the sponge will be. The sponges have porocytes on the outside which are openings the water flows into. It then flows out through an opening called the osculum. They are able to pump the water because of flagella on the inside of their cell walls (Porifera: Systematics, 2006).

Figure 5. This diagram illustrates the method sponges use in order to create water flow through their bodies. Image created by Christine Koporc.

 Video 1. This video demonstrates the water flow system in a sponge. A neon green dye was injected into the sponge and the dye can be seen coming out of the sponge on the other side. Video taken by Natalie Iannelli, edited by Christine Koporc.

Tissue Regeneration   

Sponges have the ability to regenerate their tissue. A study of the capacity of sponges to redevelop conducted at the Carmabi Marine Research Institute located in the Caribbean showed that there are three phases as to how this happens. The first phase is where the damaged surface is closed off by a scar like tissue. During phase two, the tissue changed back to the normal appearance of the surface of the sponge. The only difference is that there is a depression in the surface.The third phase is the filling of the depression. The regeneration of the sponge does depend on the species; some sponges regenerate faster than others. The ability of sponges to regenerate is an important evolutionary characteristic to their survival because they are the food source in reefs for many fish species as well as turtles (Hoppe, 1988).

Figure 6. The result of a sponge slurry regenerating. The red masses that can be seen are what has formed after a couple days since the sponge was broken down in a blender. Picture taken by Christine Koporc.

Immune System

Studying the immune response of sponges has peaked an interest in the medical community as antibiotic resistance has become more of a problem. Sponges filter a lot of water during their lifetime. That water is not only composed of the food they need to survive, but also numerous amounts of viruses, fungi, and bacteria. On the surface of the sponge there are special receptors called lipopolysaccharide or LPS which is a protein that allows them to detect bacterial endotoxins. The sponge has the capability to detect what kind material it is filtering through physical and chemical means. It also is able to rid itself of these unwanted pathogens on a molecular basis. It has what is called a LPS-interacting protein and a macrophage-expressed protein that are activated depending on what its receptors recognize. It was discovered by a man named Metchnikoff that sponges use phagocytosis to kill off bacteria as well. Phagocytosis is the ingestion of bacteria or other kinds of material by a cell. Using its detection methods and the way it kills bacteria, viruses, and fungi, the sponge is able to eliminate the unwanted organic material to keep it from dying (Wiens et al., 2005)

 

Sources:

Ackers, R. G., Moss, D., & Picton, B. E. (1992). Sponges of the British Isles (“Sponge V”) (p. 7).

Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2002). Programmed Cell Death (Apoptosis). Molecular Biology of the Cell.

Antcliffe, J.B., Callow, R.H.T., & Brasier, M.D. (2014). Giving the earliest fossil  record of sponges a squeeze. Biological Reviews, 89, 972-1004.

Blair, J. E. (2009). Animals (Metazoa). In S. B. Hedges & S. Kumar (Eds.), The Timetree of Life (p. 223). Oxford University Press.

Gehling, J.G., & Rigby, J.K. (1996) Long expected sponges from the Neoproterozoic Ediacarda fauna of south Australia. Paleontological Society, 70(2), 185-195.

Goudie, L., Norman, M. D., & Finn, J. (2013). Sponges: A Museum Victoria Field Guide (p. 18).

Hoppe, W. F. (1988). Reproductive patterns in three species of large coral reef sponges. Coral Reefs, 7, 45–50. doi:10.1007/BF00301981

Porifera: Systematics. (2006). Retrieved February 06, 2015, from http://www.ucmp.berkeley.edu/porifera/poriferasy.html

Queensland Museum. (2012). Toxic Sponges & Pharmaceutical Properties. Retrieved October 02, 2015, from http://www.qm.qld.gov.au/Find+out+about/Animals+of+Queensland/Sea+Life/Sponges/Toxic+sponges+and+pharmaceutical+properties#.VNt_EObF-gu

Sperling, E.A., Robinson, J.M., Pisani, D., & Peterson, K.J. (2010) Where’s the glass? Biomarkers, molecular clocks, and microRNAs suggest a 200-myr missing Precambrian fossil record of siliceous sponge spicules. Geobiology, 8, 24-36.

Uriz, M.-J., Turon, X., Becerro, M. A., & Agell, G. (2003). Siliceous spicules and skeleton frameworks in sponges: Origin, diversity, ultrascrutural patterns, and biological functions. Microscopy Research and Technique, 62(4), 279–299.

Wiens, M., Korzhev, M., Krasko, A., Thakur, N. L., Perović-Ottstadt, S., Breter, H. J., … Müller, W. E. G. (2005). Innate immune defense of the sponge Suberites domuncula against bacteria involves a MyD88-dependent signaling pathway: Induction of a perforin-like molecule. Journal of Biological Chemistry, 280(30), 27949–27959. doi:10.1074/jbc.M504049200

Werner, E., & Muller, G. (2003). The Origin of Metazoan Complexity: Porifera as Integrated Animals. Integrative & Comparative Biology, 43(1), 3–10.

Wörheide, M., Erpenbeck, D., Larroux, D., Maldonado, C.,  Voigt, M. , C. B. and D. V. L. (2012). Deep Phylogeny and Evolution of Sponges (Phylum Porifera). Advances in Marine Biology, 61.