Phylum Porifera

Topics: Sponge, Sclerocyte, Poriferans Pages: 4 (1062 words) Published: April 16, 2013
1Department of Biology, College of Science, University of the Philippines Baguio July 17, 2012

| | |Sponges [Porifera] are unusual animals whose body plans make interpreting phylogenetic relationships within the group and with other basal | |metazoan taxa a difficult task. In this exercise, different species of Poriferans were observed. It will be used then to determine their | |defining characteristics as an invertebrate. The skeletal elements of the Poriferans, the spicules, are formed enzymatically by the anabolic | |enzyme silicatein and the catabolic enzyme silicase. Both, the spicules of Poriferans, comprise a basal skeleton made up of calcium carbonate,| |central axial canal and an axial filament which harbors the silicatein. The data collected here substantiate the findings that Poriferans | |still exist. These findings are makes us further understand the basic pathways in the body plan formation of sponges. |

Poriferans get their nutrition by staying in one place, pumping water through themselves, and filtering it for small organisms and bits of food that they digest. Sponges are protected from predators by their low nutrition content as well as irritating spines distributed throughout their bodies, called spicules, which also double as a "skeleton. The spicules are secreted by specialized mesenchyme cells known as scleroblasts. Scleroblast secreting a calcareous spicule is called calcoblast while that producing a siliceous spicule is called silicoblast.

All the activities of their body of the sponges depend on the current of water entering through ostia and passing out through osculum or oscula. Inside the body, water current flows through system of spaces which collectively...
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