Editing Sponge (section)

=== Respiration, feeding and excretion ===

[[File:Venus Flower Basket.jpg|thumb|''[[Euplectella aspergillum]]'', a [[glass sponge]] known as "Venus's flower basket"]]

Sponges do not have distinct [[circulatory]], [[respiratory]], [[digestion|digestive]], and [[excretory]] systems – instead, the water flow system supports all these functions. They [[filter feeding|filter]] food particles out of the water flowing through them. Particles larger than 50&nbsp;micrometers cannot enter the [[wikt:ostium|ostia]] and [[pinacocyte]]s consume them by [[phagocytosis]] (engulfing and intracellular digestion). Particles from 0.5&nbsp;μm to 50&nbsp;μm are trapped in the ostia, which taper from the outer to inner ends. These particles are consumed by pinacocytes or by [[archaeocyte]]s which partially extrude themselves through the walls of the ostia. Bacteria-sized particles, below 0.5&nbsp;micrometers, pass through the ostia and are caught and consumed by [[choanocyte]]s.<ref name="Ruppert_2004"/> Since the smallest particles are by far the most common, choanocytes typically capture 80% of a sponge's food supply.<ref name="Bergquist_2001">{{cite book |contribution=Porifera (Sponges) |last=Bergquist |first=P.R. |title=Encyclopedia of Life Sciences |year=2001 |publisher= John Wiley & Sons |doi=10.1038/npg.els.0001582 |isbn=978-0-470-01617-6}}</ref> Archaeocytes transport food packaged in [[Vesicle (biology)|vesicles]] from cells that directly digest food to those that do not. At least one species of sponge has internal fibers that function as tracks for use by nutrient-carrying archaeocytes,<ref name="Ruppert_2004"/> and these tracks also move inert objects.<ref name="Bergquist_1998"/>

It used to be claimed that [[glass sponge]]s could live on nutrients dissolved in sea water and were very averse to silt.<ref name="Krautter_1998">{{cite journal |last=Krautter |first=M. |title=Ecology of siliceous sponges: Application to the environmental interpretation of the Upper Jurassic sponge facies (Oxfordian) from Spain |journal=[[Journal of Iberian Geology|Cuadernos de Geología Ibérica]] |pages=223–239 |year=1998 |volume=24 |url=http://www.ucm.es/BUCM/revistas/geo/16986180/articulos/JIGE9898110223A.PDF |archive-url=https://web.archive.org/web/20090319205858/http://www.ucm.es/BUCM/revistas/geo/16986180/articulos/JIGE9898110223A.PDF |archive-date=March 19, 2009 |access-date=2008-10-10 |url-status=dead }}</ref> However, a study in 2007 found no evidence of this and concluded that they extract bacteria and other micro-organisms from water very efficiently (about 79%) and process suspended sediment grains to extract such prey.<ref>{{cite journal |doi=10.4319/lo.2007.52.1.0428 |author1=Yahel, G. |author2=Whitney, F. |author3=Reiswig, H.M. |author4=Eerkes-Medrano, D.I. |author5=Leys, S.P. |year=2007 |title=In situ feeding and metabolism of glass sponges (Hexactinellida, Porifera) studied in a deep temperate fjord with a remotely operated submersible |journal=[[Limnology and Oceanography]] |volume=52|issue=1|pages=428–440|citeseerx=10.1.1.597.9627|bibcode=2007LimOc..52..428Y|s2cid=86297053 }}</ref> Collar bodies digest food and distribute it wrapped in vesicles that are transported by [[dynein]] "motor" molecules along bundles of [[microtubule]]s that run throughout the [[syncytium]].<ref name="Ruppert_2004"/>

Sponges' cells absorb oxygen by [[diffusion]] from water into cells as water flows through body, into which [[carbon dioxide]] and other soluble waste products such as [[ammonia]] also diffuse. Archeocytes remove mineral particles that threaten to block the ostia, transport them through the mesohyl and generally dump them into the outgoing water current, although some species incorporate them into their skeletons.<ref name="Ruppert_2004"/>