Porifera
Jesse Carmen
"Porifera" are sponges.

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This is a common sea sponge. Sea sponges like these are thought to be the first truly multicellular organisms ever. (JAC) http://www.ri.net/schools/West_Warwick/manateeproject/ocean/animals.htm

I. Diagnostic Characteristics that define the Group

One definite characteristic of sponges is that they are sedate and barely move. Because of their lack of motion, some scientists even mistake sponges for plants! Also, sponges have porous bodies. Lastly, sponges do not have specialized nerve or muscle tissue (a group of cells with a common purpose). This is very interesting since nerve and muscle tissue is a characteristic of animals, and sponges are in the animal kingdom. Instead, sponges are composed of different types of cells that have their own specific function which serve to benefit a sponge. However, sponges are sometimes said to be a sub-kingdom of their own. Sponges are very diverse in apperance, size and complexity. Sponges can take the shape of small tubes, large sheets or even resemble elephant ears. All sponges also have canal systems (sponges get their food directly from the nutrients in the water so filtering water is how they eat); water is absorbed by the pores, goes through various canals to reach the spongocoel and then exit the sponge through the osculum. Sponges vary in complexity because when they increase in size , they increase in folds of the outer cells and then the sponge creates the need for more canals to allow all its cells to be fed. (10 SV).

There are three different groups of sponges: the Hexactinellida, the Demospongia, and the Calcarea. The Hexactinellids are "glass sponges." They have a skeleton made of siliceous spicules (spicules are sharp, needle-like structures). Siliceous means that a material is made of silicates, which are chemical compounds made of silicon and oxygen. The spicules of Hexactinellids form six rays. Most of the tissue of a hexactinellid is made of a single large cell, with several nuclei. This allows it room to make spicules inside the cell (3). Demonspongia are the most diverse sponge group. Demospongiae also form spicules (5), but they differ from Hexactinellida in that their body shapes are not symmetrical, and they form one- to four-rayed spicules instead of six-rayed spicules (4). Members of Calcarea have spicules made out of calcium carbonate -- a compound made of calcium, carbon, and oxygen -- unlike the other other two groups. They are mostly found in shallow waters (5). [HZ]
There are three morphologic dividing categories in sponges. Asconoid sponges have a single tubular body perforated by pores. Syconoid sponges also have a tubular body with a single osculum. Leuconoid sponges on the other hand have many tubes and canals that lead to different chambers lined with flagellated cells (11, NK).

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This is a diagram of a part of the outer wall of a "glass sponge." You can clearly see the six-ray spicules inside the wall of the sponge. Choanocyte cells are also visible in the diagram (HZ).

II. Acquiring and Digesting Food

Porifera diet consists of bacteria and other organic matter (SES 15). Some feed on green algae, dinoflagellates, and cyanobacteria (SES 15). The water that flows thourgh provides the sponge with its food(8 VM). Sponges are known as “suspension feeders.” Sponges collect nutrients from the water through their choanocyte cells. About 90% of the bacteria in the water that flows through them (which is pushed through with the help of beating flagella) is absorbed as nutrients (SES 15). The choanocyte cells consist of a flagella surrounded by a collar cell. As the choanocyte cells uptake the food, the flagella (a cellular 'tail' that aids in motion) creates a water current and the collar cells ingest the food. The choanocytes take up the nutrients through phagocytosis. Phagocytosis is the uptaking of large food particles. Sponges also consist of amoebocytes, which along with discarding of foreign bodies also are responsible for uptaking nutrients from the water and from choanocyte cells. Once amoebocytes uptake the nutrients, they digest these nutrients and then transport the nutrients to other cells.
While the vast majority of Porifera are filter feeders that use the method explained above to acquire food, there are a few noted species of carnivorous Porifera, most from the family Cladorhizidae and a few from the families Guitarridae and Esperiopsidae. These species occur where the supply of food particles is relatively low; they prey on crustaceans and other small animals. Little is known on how most of these species capture their prey. Various theories include the use of sticky threads, hooks, or venom. Most carnivorous sponges have completely lost their water flow system. (14 Nangia)


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    • This drawing shows the many different parts that sponges are composed of:

Porocytes- doughtnut-shaped cells that align the body wall.
Choanocytes- flagellated cells that aid in circulation, water movement, and digestion.
Amoebocytes- cells that are important in getting rid of foreign bodies.
Mesohyl- a part of the sponge that separates the two layers of the sponge.
Spongocoel- the mid- cavity (compartment) of the sponge.
Osculum- larger openings within the sponge where water is passed through. (More complex sponges have more osculum)
Epidermis- tightly packed cells aligning the sponge.
Spicules- makes up the skeleton of the organism, they provide the support need to keep the pores open. Spicules are made of calcium carbonate and silica, or the organic substance spongin. (12) (RK)





    • The right-handed drawing is an enlarged version of a choanocyte cell. The drawing shows the different components of the choanocyte cell: the flagella and the collar cell. It also demonstrates the uptaking of food by phagocytosis. At the end of the choanocyte is an amoebocyte cell, which is responsible for getting rid of foreign bodies.

A sponge with a very large central cavity. (ER) (18)
A sponge with a very large central cavity. (ER) (18)



III. Sensing the Environment/ Self-protection

Amoebocytes also utilize phagocytosis to protect the sponge. As the amoebocytes sense the surrounding environment of the sponge, they recognize anything that is wrong, and correct this by eliminating all foreign bodies through phagocytosis. In addition, some sponges protect themselves with sharp silica spicules called gemmoscleres (9, DJ). These spicules or spikes float around water and have been known to cause eye lesions in swimmers of these waters (9, DJ). Sponges use chemical defense against environmental stress factors like predation. It is also said that sponges that are growing exposed instead of unexposed are more toxic. (6. Sharma)



IV. Reproduction

Sponges are hermaphrodites, which means that they have male and female reproductive parts. Sponges also produce female and male gametes (sperm and egg). Egg and sperm arise from the choanocyte and amoebocyte cells of the sponge. The eggs of sponges are housed in the mesohyl. The sperm is carried out through the water current that circulates the sponge. Sperm are created, concentrated and sent out the excurrent openings, sometimes in masses so dense that the sponges appear to be smoking(8 VM). The temperature of the water that the sponges live in usually determine when the sponges release the sperm (14 BL). These sperm are then captured by female sponges of the same species(8 VM). When the sperm enters a collar cell of a neighboring sponge, the collar cell loses its collar, transforming the cell into a specialized cell that brings the sperm to the eggs (2) (DP). Fertilization (the combination of egg and sperm) occurs in the mesohyl of the sponge. Sponges can also reproduce asexually (by not having sex) as pieces of the sponge break off and are then repaired. Some species will make internal buds, called gemmules, that can survive in extreme conditions which the rest of the sponge cannot survive in (2) (DP). Some sponges reproduce asexually (8 VM).
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(17)(RJS)

V. Osmotic Balance/ Circulation/ Respiration/ Waste Removal System

Since a sponge is composed of pores, water is brought from the pores into the spongocoel, which is the central cavity (or compartment) of the sponge. Then, from the spongocoel, the water goes out the osculum, which is a larger opening of the sponge. Sometimes cells circulating the pores and the osculum close, ensuring osmotic balance within the sponge. A water current is constantly circulating throughout the sponge, serving as a circulation system. Also, since the water flows into the spongocoel and out of the osculum the movement of water throughout the sponge serves as a waste removal system. Lastly, the movement of water (osmosis) into and out of the sponge serves as a type of respiration system. Water is substituted for the gases that are usually entering and leaving an animals body.

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This pictures gives a clear representation of the central cavity of a porifera, which is where the water is brought into.
(16,GR)


VI. Locomotion


Sponges don’t have any locomotion because one of the diagnostic characteristics of a sponge is that they are sedate and do not move. Most sites confirm that adult sponges are largely sessile, living in an attached position. However, it has been noted that certain sponges can move slowly by directing their water current in a certain direction with the beating of their flagella. Sponges may move to quiet clear waters, because if the sediment is agitated by wave action or by currents, it tends to block the pores of the organism, lessening its ability to feed and survive. (7) (SS)
Some sponges can move along the bottom at a rate of between one and four millimeters per day with the help of ameba-like movements of their pinacocytes, the outer layer of cells. Some species of sponges can move by contracting their entire bodies as well. (2) (KN)

VII. Thermoregulation

A sponge doesn't have any specific system of thermoregulation (regulation of an internal environment). A sponge's temperature depends on the temperature of its habitat, which is the water that it is living in. Sponges can live in any type of aquatic environment, no matter the temperature of the water. They are most likely to be found in marine environments. (13 HS)

Review Questions
1. What does it mean for a sponge to be "siliceous" ? [OZ]
2. Explain how sponges use choanocyte cells to intake nutrients from water. (AR)
3. List 2 ways sponges defend themselves.(SJB)
4. Explain how a sponge would reproduce sexually. (BMB)
Source(s):

Campbell, Neil A., and Jane B. Reece. Biology. 6th ed. Boston: Benjamin-Cummings Company, 2002.
2.) Myers, P. 2001. "Porifera", Animal Diversity Web. December 01, 2008. <http://animaldiversity.ummz.umich.edu/site/accounts/information/Porifera.html>.
3.) "Hexactinellida." Palaeos: The Trace of Life On Earth. December 3, 2008 <http://www.palaeos.com/Invertebrates/Porifera/Hexactinellida.html>.
4.) Wheeler, K. 2001. "Demospongiae." Animal Diversity Web. December 04, 2008 <http://animaldiversity.ummz.umich.edu/site/accounts/information/Demospongiae.html
>.
5.) "Calcarea." University of California Museum of Paleontology. Dec 4, 2008 <http://www.ucmp.berkeley.edu/porifera>.
6.) Proksch,P. Defensive roles for secondary metabolites from marine sponges and sponge-feeding nudibranchs. <http://lib.bioinfo.pl/pmid:7940572>
7.) Myers, Phil. "Porifera." Animal Diversity Web. University of Michigan. 7 Dec. 2008 <http://animaldiversity.ummz.umich.edu/site/accounts/information/porifera.html>.
8.) "Porifera: Life History and Ecology." 7 Dec. 2008 <http://www.ucmp.berkeley.edu/porifera/poriferalh.html>
9.) Clarke, Matt. "Hundreds injured by freshwater sponges." Practical Fishkeeping 14 Feb. 2007.
10)"Porifera: More on Morphology." 8 Dec. 2008 <http://www.ucmp.berkeley.edu/porifera/poriferamm.html>
11)Myers, P. 2001. "Porifera" (On-line), Animal Diversity Web. Accessed December 11, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Porifera.html
12) "Porifera (sponges)." 1997. 14 Dec. 2008 <http://www.bumblebee.org/invertebrates/Porifera.htm>.
13) Myers, Phil. "Phylum Porifera." Animal Diversity Web
. 2008. University of Michigan Museum of Zoology. 14 Dec. 2008 <http://animaldiversity.ummz.umich.edu/site/accounts/information/porifera.html>.
14) "sponge."
Encyclopædia Britannica. 2008. Encyclopædia Britannica Online. 16 Dec. 2008 <http://www.britannica.com/EBchecked/topic/560783/sponge>.
15) "Typical Sponge Feeding."
Porifera: Life History and Ecology. 17 Dec. 2008. <http://www.ucmp.berkeley.edu/porifera/poriferalh.html>
16) "Sponge Structure."
Sponges__. 18 Dec. 2008 <http://www.trc.ucdavis.edu/.../bis10v/week9/07sponges.html>.
17)"Phylum Porifera (sponges)." 18 Dec 2008 <http://siera104.com/bio/porifera.html>.
18) http://ccma.nos.noaa.gov/reef_fish_photos/PORBTV_4_STJ_07_05.jpg
Page Edited by: DP, Hanna Z, Yasheka Sharma, Josh Czik, SS, Kevin Nayer, Vonai Moyo, Daisy Joo, Sarah Vlach, NK, Rachel Kornetsky, Hilary Stepansky, Becca Levenson, Sam Blatchford, Sarah Schwarzschild, GR, Ethan Ricman, Meru Nangia, Brittany Marcus-Blank