![]() The mesohyl is penetrated by a complex system of canals and choanocyte chambers (termed the aquiferous system), which is the most characteristic feature of the poriferan anatomy. The rigidity of the spongeīody is ensured by the collagen and spongin fibrils (in some Demospongiae orders) and by the internal inorganic skeleton, consisting of either calcium carbonate (CaCO 3) (Calcarea, some Demospongiae) or silica (SiO 2) (Hexactinellida, Demospongiae, many Homoscleromorpha). Is covered by a simple single-layered flat epithelium (called exopinacoderm), while the internal parts of the animal body are occupied by a highly complex mesenchymal tissue (called mesohyl) that comprises numerous mobile cell types embedded in its extracellular matrix. Their organization is peculiar: they have no distinct gut, muscles, gonads, nervous system, or respiratory system. The body size of sponges varies as much as their body shapes: from 3–10 mm to 1.5–2 m. The body shape of sponges is very diverse they may be film-like, encrusting, lumpy or spherical, tubular, branching, flabellate, and so on. As such, they represent a key group for the understanding of the evolutionary history of animals, including the origin and evolution of regeneration mechanisms. Porifera) are thought to be the sister group of all other animalsĪnd the earliest branching multicellular lineage of extant animals. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |