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Sponges constitute the phylum Porifera, and have been defined as sessile metazoans (multicelled immobile animals) that have water intake and outlet openings connected by chambers lined with choanocytes, cells with whip-like flagella. [13]: 29 However, a few carnivorous sponges have lost these water flow systems and the choanocytes.
Demosponges (Demospongiae) are the most diverse class in the phylum Porifera. They include greater than 90% of all species of sponges with nearly 8,800 species worldwide (World Porifera Database). [5] They are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite [citation ...
Parazoa (Parazoa, gr. Παρα-, para, "next to", and ζωα, zoa, "animals") are a taxon with sub-kingdom category that is located at the base of the phylogenetic tree of the animal kingdom in opposition to the sub-kingdom Eumetazoa; they group together the most primitive forms, characterized by not having proper tissues or that, in any case, these tissues are only partially differentiated.
Some molecular analyses suggest the class Calcarea is not exclusively related to other sponges, and should thus be designated as a phylum. This would also render Porifera (the sponge phylum) paraphyletic. Borchiellini et al. (2001) argued that calcareans were more closely related to Eumetazoa (non-sponge animals) than to other sponges. [9]
Spongilla lacustris is part of the class demosponges of the phylum Porifera. The Porifera phylum contains all sponges which are characterized by the small pores on the outer layer, which take in water. The cells in the sponge walls filter food from the water. Whatever is not uptaken by the sponge is pumped through the body out of a large opening.
Amphimedon compressa can grow to a length of 40 cm (16 in) and a diameter of 4 cm (1.6 in), but it is usually smaller in shallow water. The tree-like curved branches grow from a basal encrusting mass, but very occasionally this sponge grows as a small, unbranched, flattened hemisphere.
Porifera are suspension feeders, meaning they can filter plankton and other microorganisms through its osculum. Porifera contain choanocytes , pinacocytes , and archeocytes . The structure of the choanocyte being a singular flagellum surrounded by microvilli is a characteristic of most porifera which allows water to enter.
As members of the oldest phylum of metazoans, Suberites serve as model organisms to elucidate features of the earliest animals. [2] [3] [4] Suberites and their relatives are used to determine the structure of the first metazoans [2] and have been studied to determine how totipotency has replaced by pluripotency in most higher animals. [5]