http://ucmp1.berkeley.edu/porifera/porifera.html (Einblicke ins Internet, 10/1995)Porifera are commonly referred to as sponges. Living sponges are believed to be the legacy of the first major branch in animal history. Thus, they are considered to be the "sister group" of all other metazoans, i.e. animals. The fossil record of sponges extends back to the "Cambrian Explosion", some 530 million years ago, when the first animals with skeletons burst into the world with a bewildering diversity of form.
Poriferans are sedentary animals, and feed by filtering tiny particles out of the water in which they live. Poriferans don't have mouths. Instead, they have tiny pores in their outer walls through which water is drawn. Cells in the sponge walls filter goodies from the water as the water is pumped through the body and out other openings called excurrent pores if they are small or oscula if they are big. You can see the large opening at the top of the sponges shown above. These are the sponges' oscula.
There is one known exception to the general description of sponge feeding that you just read above. One recently discovered sponge species is actually carnivorous, preying upon tiny crustaceans that get entangled in the sponge's spicules. This sponge still ingests its food on a cell-by-cell basis.
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The sponges in the diagram above are Clathria basilana (Levi, 1959) and Haliclona fascigera (Hentschel, 1912). Identification provided over the net by spongiologist Rob van Soest of the Institute for Systematics and Population Biology (Zoologisch Museum), University of Amsterdam. Thanks!
