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The phylum Porifera is further divided into classes mainly according to the composition of their skeletons: [17] [29] Hexactinellida (glass sponges) have silicate spicules, the largest of which have six rays and may be individual or fused. [17] The main components of their bodies are syncytia in which large numbers of cell share a single ...
Sponges, known scientifically as Porifera, are the oldest metazoans and are used to elucidate the basics of multicellular evolution. [2] These living fossils are ideal for studying the principal features of metazoans, such as extracellular matrix interactions, signal-receptor systems, nervous or sensory systems, and primitive immune systems.
Homoscleromorpha is phylogenetically well separated from Demospongiae. [4] Therefore, it has been recognized as the fourth class of sponges. [5] [6]It has been suggested that Homoscleromorpha are more closely related to eumetazoans than to the other sponge groups, rendering sponges paraphyletic. [7]
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] A few studies have also supported a sister group relationship between calcareans and Ctenophora (comb jellies). Many authors have strongly ...
A major radiation occurred in the Lower Cambrian and further major radiations in the Ordovician possibly from the middle Cambrian. [12] The Systema Porifera (2002) book (2 volumes) was the result of a collaboration of 45 researchers from 17 countries led by editors J. N. A. Hooper and R. W. M. van Soest. [13]
Based on the discovery that the Porifera share one common ancestor, the Urmetazoa, with the other animals, [25] [26] it was deduced that these animals represent the oldest, still extant animal taxon. Even more, the emergence of these animals could be calculated back to 650–665 million years ago [Ma], a date that was confirmed by fossils ...
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.
The siliceous sponges form a major group of the phylum Porifera, consisting of classes Demospongiae and Hexactinellida. They are characterized by spicules made out of silicon dioxide, unlike calcareous sponges. Individual siliachoates (silica skeleton scaffolding) can be arranged tightly within the sponginocyte or crosshatched and fused together.