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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.
Hexactinellid sponges are sponges with a skeleton made of four- and/or six-pointed siliceous spicules, often referred to as glass sponges. They are usually classified along with other sponges in the phylum Porifera , but some researchers consider them sufficiently distinct to deserve their own phylum, Symplasma .
However, molecular and morphological evidence show that the Homoscleromorpha do not belong in this class. The Homoscleromorpha was therefore officially taken out of the Demospongiae in 2012, and became the fourth class of phylum Porifera. [14] Nevadacoelia wistae, a fossil anthaspidellid demosponge from the early Ordovician of Nevada.
Porifera (sponges), multicellular organisms that have bodies full of pores and channels allowing water to circulate through them; Priapulida, or penis worms, are a phylum of marine worms that live marine mud. They are named for their extensible spiny proboscis, which, in some species, may have a shape like that of a human penis;
Of this group only surviving sponges, which belong to the phylum Porifera, and Trichoplax in the phylum Placozoa. Parazoa do not show any body symmetry (they are asymmetric); all other groups of animals show some kind of symmetry. There are currently 5000 species, 150 of which are freshwater. The larvae are planktonic and the adults are sessile.
The phylum Porifera includes the aquatic fauna sponges. Subcategories. ... Sponges and humans (2 C, 2 P) P. Prehistoric sponges (6 C, 4 P) T. Sponge taxa by rank (5 C)
These sponges are massive or encrusting in form and have a very simple structure with very little variation in spicule form (all spicules tend to be very small). Reproduction is viviparous and the larva is an oval form known as an amphiblastula. This form is usual in calcareous sponges but is less common in other sponges.
Using their ostia and osculum these sponges filter the water for various small aquatic organisms such as protozoans, bacteria, and other free-floating pond life. [4] Sponges of the genus Spongilla partake in symbiotic relationships with green algae, zoochlorellae. The symbiotic zoochlorellae give the sponges a green appearance and without them ...