Animalia-porifera

__**Porifera**__ By Paul Southard **__Diagnostic Characteristics:__**

Sponges have no organized tissues, they are just masses of specialized cells with no symmetry and very little organization. In fact, they are the only branch of the kingdom animalia with no tissues. Because of this, they have no organs and no nervous system. They are very similar to the choanoflagellates, small colonies of protists in the ocean from which animals evolved, and very similar to colonies in general, only slightly more organized and specialized. They live in ocean water, except for about a hundred species that can live in fresh water. Sponges can form all different shapes, such as fans, cups, cones, tubes, blobs, barrels, and crusts. They range in size from just a few millimeters to two meters tall. There are 5,000 to 10,000 known species of sponges. (IL)

Porifera have three distinct types of specialized cells. **Choanocytes** are flagellated cells meant for feeding with either phagocytosis or pinocytosis. **Archaeocytes** are ameboid cells that are free to move around within the mesophyl and can secrete spicules and collagen fibers. **Pinacocytes** are cells that from the epidermis that covers the sponge- these are just flat, thing epithelial cells with a limited contractile ability. (JP- Source 2) Amoebocytes, the specialized cells that serve to digest and transport food around the sponge, also contribute to the formation of the structure of sponges. As they move around the sponge, they secrete spicules, which are hard structural fibers made out of calcium carbonate or silica. Some sponges have amoebocytes that secrete elastic protein fibers made of collagen that create a skeleton called spongin. The structure of the sponges’ skeletons is what helps to divide them into the three different classes. (MR; Source 21)

The Porifera phylum is divided into three classes based on skeleton type; these classes entail the Calcispongiae, Hyalspongiae, and Demospongiae. (ZJ)

Calcispongiae: Found in shallow coastal waters, this class possesses distinctive spicules (tiny spike like structures) that are composed of calcium carbonate. This class of porifera is the smallest, where all species do not exceed a height of 10 centimeters. (ZJ)

Hyalspongiae: Commonly known as glass sponges, this class is known as the most symmetrical and individualized class. The spicules of this class are triaxon, meaning that they are six pointed. (ZJ)

Demospongiae: Containing the greatest number of sponge species, this class of porifera has variable shape, size, and composition of its skelaton. Some species in this group have siliceous spicules while others possess a skeleton composed of spongin fibers. (ZJ- source 10) Porifera have totipotency where a cell of the organism can generate part of or the entire organism. (AR)


 * = [[image:shsapbiop2-taxa/choan.png width="307" height="424" align="center" caption="A choanoflagellate"]] ||= [[image:http://www.emc.maricopa.edu/faculty/farabee/biobk/sponge_1.gif width="306" height="394" align="center" caption="Figure 2. Sponge Structure (RK)"]] ||

(AP)

__**Acquiring and Digesting Food:**__

Sponges are suspension feeders. The sponge absorbs water through its pores into a cavity in its center: the spongocoel. The cavity is fairly large in relation to the sponge. The water flows out of the sponge through the osculum. The sponge collects food from the water that enters its spongocoel. The spongocoel is lined by choanocytes, which consists of a main cell with a collar and a flagellum. The cells use the flagellum to propel water into the collar, where it is filtered for food particles. The cells then use phagocytosis to consume the food particles. The choanocytes are grouped in chambers. The structure of the pincoderm are such that they direct water into these chambers so the sponge can maximize its feeding ability. (LPE) After a collar cell collects enough nutrients, another type of cell called an **amoebocyte** will transfer the food to other cells within the sponge. Second, the back and forth beating of the flagella drives water into the canals. The water makes collecting nutriends and oxygen possible, and carbon dioxide and waste easy to remove. The forces water through the sponge work to keep the animal alive and healthy. (RW)

__**Sensing the Environment:**__ They have no nervous system, so single cells have to detect changes in the environment. They are so sedate that many thought they were plants. The main movement is that of the flagella on the choanocytes, which beat water into the cells. There are also specialized amoebocyte cells that transport nutrients from the choanocytes to other cells.
 * __Locomotion:__**

Although porifera are considered immobile, due to coordinated movements of cells, the organism has behavioral patterns like crawling, production of filament body extensions, and contractions of the body. (AR)



The sponge itself cannot perform respiration, but individual cells do with the nutrients they recieve from the amoebocytes.
 * __Respiration:__**

The sponge consists of singular cells, and these individual cells all have their own form of individual respiratin by which they absorb oxygen from the passing stream of water. This is because the entire clump of cells of which the sponge consists doesn't have an overall respiratory mechanism. (JP)

__**Metabolic Waste Removal:**__ The individual cells of the organism exchange waste with environment, because they all touch water.

They have a simple excretory system called protonephridia. This system con

Sponges have collar cells inside of their pores. These cells have flagella that move back and forth in order to force water through the sponge. This allows nutrients and oxygen while also getting rid of waste such as carbon dioxide. (CP source 3) __**Circulation:**__ Sponges have no circulatory system, but water does flow around the cells constantly, creating a substance for the cells to exchange materials with. Sponges are interesting because unlike other animals, theyre contstantly changing ane reorganizing in the effort to become more efficient at circulating water. (LPE) __**Self Protection:**__ Sponges have no defense mechanisms. If fragments do break off of them, though, they can reproduce asexually and form another sponge. Many sources state that the sharp spicules on a sponge, whose original function was to be components of its skeleton, are effective in fending off predators. Also, many sponges secrete toxic chemicals which especially taste or smell bad to predators. (SP)

__**Osmotic Balance:**__ Porifera have all their cells working to have osmotic balance individually. The cells are forced to do this because they have no specialization. (RJ)

__**Temperature Balance:**__ Porifera lack any sophisticated method of maintaining homeostasis. Because the cell layers are in constant contact with the surrounding environment (water), porifera are whatever temperature their environment is. In addition, because porifera are sessile, they cannot move to a new area if the temperature becomes inhospitable. As a result, porifera only grow in environments whose temperature is suitable for them. (Matt B - Source 9)

Sponges are capable of reproducing both asexually and sexually. Sponges that reproduce sexually are considered hermaphroditic, meaning they have both female and male sex organs, or in this case, cells that can either produce sperm or eggs. Most sponges have sequential hemaphroditism; they function as one sex for a period of time and then change to the other sex, preventing self-fertilization. (SP) Asexually, sponges reproduce by a method called budding, which is a form of asexual reproduction in which a new organism grows on another one. The new organism remains attached as it grows, separating from the parent organism only when it is mature. Asexual include fragmentation, budding, and **gemmules** (amoebocytic sporulation). Sexual reproduction is carried out by releasing sperm into the current. Fertilization is internal and occurs when sponges filter the sperm from the current (MP). Although the adult is sessile, the zygote matures into a ciliated larva and swims to new areas to implant itself. (SP)
 * __Reproduction:__**

To add on to the sexual reproduction of sponges, while most sponges are hermaphroditic, they can only be one gender at a time. During the reproductive period of a sponge, certain areas of the sponge will become differentiated to produce either sperm or ova. Sperm produced by a sponge is released into the canals of a sponge and then pumped out through the osculum, an excretory structure of the sponge. Once out of the sponge, the sperm is drawn into the canal system of another sponge and trapped by the choanocytes which then loose their flagellum and collar. Then, the sperm iS transferred to the ovocyte ( a cell generating ova), assuming that the sponge is in its female form. (VN)

When reproducing asexually, sea sponges form **gemmules**. External buds are formed when fragments of a sea sponge's body are broken off by water currents and carried to other locations. There the buds begin to grow into clones, or genetically identical sponges, of their parents. Some species will produce buds internally rather than externally. These buds are made to survive in extremely unfavorable conditions and this may result in the death of the parent sponge.(RW)

Fossil Record Porifera fossil record starts around the Precambrian period, where many species were fossilized. Reef formation was greatly contributed to by porifera in the Phanerozoic period. (CM) Porifera have been often recognized as the first animals to evolve because of their early presence in the fossil record. As stated prior they first appeared in the Precambrian period and became wide spread by the Cambrian era. During the Paleozoic and Mesozoic era porifera began to diversify into many new species. The greatest amount of species developed in the Cretaceous period. (MS 18)

__**Review Questions**__ 1. How is the sponge capable of producing both sexually and asexually? Answer this question and then choose two below. a) Describe in detail the three process of reproducing asexually. b) How is sexual reproduction carried out in the sponge? b) Describe in detail sequential hemaphrodism and why it is utilized. d) Describe gemmules in detail. (MB) 2) Explain why sponges are classified as animals, and state examples of certain characteristics which may lead one to believe sponges are part of the kingdom Plantae. (SP) Sources:

http://www.ucmp.berkeley.edu/porifera/poriferalh.html (TB) [] LPE 2. http://biosciweb.net/animal/pdf/porif.pdf 3. "Life of a Sponge." //Tree of Life Web Project//. Web. 29 Oct. 2011. . (CP) 4. [](MP) 5. [] (MM) 6. Figure 2. [](RK) 7. "Introduction to Animals, Sponges, Cnidarians." Web. 30 Oct. 2011. . 8. "Branches on the Tree of Life: Sponges." //Home Page//. Web. 30 Oct. 2011. . 9. http://www.kgs.ku.edu/Extension/fossils/sponge.html (Matt B) 10. Barnes, Robert. // Invertebrate Zoology //. 2nd. Philadelphia, PA: W.B. Saunders Company, 1969. Print. 11. [|http://universe-review.ca/R10-33-anatomy.htm#sponges] (JP) 12. [] (AR) 13. [] (AR) 14. "The Sponges (Phylum Porifera)." // The Earth Life Web //. Web. 11 Nov. 2011. . (VN) 15.[] (AP) 16.[] (RW) 17 [] (JS) 18. "Porifera Fossils." //Fossils Geological Time and Evolution//. Web. 13 Nov. 2011. []. (MS) 19.[] (RW) 20. "Sponges." //EnchantedLearning.com//. Enchanted Learning. Web. 14 Nov. 2011. . (IL) 21. "Porifera." //Animal Sciences//. Ed. Allan B. Cobb. New York: Macmillan Reference USA, 2010. //Gale Science In Context//. Web. 30 Nov. 2011.