Editing Hexactinellid (section)

=== Syncytia ===
Bodies of glass sponges are different from those other sponges in various other ways. For example, most of their cytoplasm is not divided into separate cells by membranes, but forms a [[syncytium]] or continuous mass of cytoplasm with many [[cell nucleus|nuclei]] (e.g., Reiswig and Mackie, 1983); it is held suspended like a [[spider web|cobweb]] by a [[scaffolding]]-like framework made of [[silica]] spicules.<ref name="Ruppert_2004" /> The remaining cells are connected to the syncytium by bridges of [[cytoplasm]]ic "rivers" that transport nuclei, [[organelle]]s ("organs" within cells) and other substances.<ref name="Leys_2003">{{cite journal | vauthors = Leys SP | title = The significance of syncytial tissues for the position of the hexactinellida in the metazoa | journal = Integrative and Comparative Biology | volume = 43 | issue = 1 | pages = 19–27 | date = February 2003 | pmid = 21680406 | doi = 10.1093/icb/43.1.19 | doi-access = free }}</ref> Instead of choanocytes, these bridges have further syncytia, known as choanosyncytia, which form bell-shaped chambers where water enters via perforations. The insides of these chambers are lined with "collar bodies", each consisting of a collar and flagellum but without a nucleus of its own. The motion of the flagella sucks water through passages in the "cobweb" and expels it via the open ends of the bell-shaped chambers.<ref name="Ruppert_2004" />

Some types of cells have a single nucleus and membrane each but are connected to other single-nucleus cells and to the main syncytium by "bridges" made of [[cytoplasm]]. The [[sclerocyte]]s that build spicules have multiple nuclei, and in glass sponge larvae they are connected to other tissues by cytoplasm bridges; such connections between sclerocytes have not so far been found in adults, but this may simply reflect the difficulty of investigating such small-scale features. The bridges are controlled by "plugged junctions" that apparently permit some substances to pass while blocking others.<ref name="Leys_2003" />

This physiology is what allows for a greater flow of ions and electrical signals to move throughout the organism, with around 75% of the sponge tissue being fused in this way.<ref name="Nishi 739–747" /> Another way is their role in the nutrient cycles of deep-sea environments. One species for example, ''Vazella pourtalesii'', has an abundance of symbiotic microbes which aid in the nitrification and denitrification of the communities in which they are present. These interactions help the sponges survive in the low-oxygen conditions of the depths.<ref>{{Cite journal |last1=Maldonado |first1=Manuel |last2=López-Acosta |first2=María |last3=Busch |first3=Kathrin |last4=Slaby |first4=Beate M. |last5=Bayer |first5=Kristina |last6=Beazley |first6=Lindsay |last7=Hentschel |first7=Ute |last8=Kenchington |first8=Ellen |last9=Rapp |first9=Hans Tore |date=2021 |title=A Microbial Nitrogen Engine Modulated by Bacteriosyncytia in Hexactinellid Sponges: Ecological Implications for Deep-Sea Communities |journal=Frontiers in Marine Science |volume=8 |doi=10.3389/fmars.2021.638505 |issn=2296-7745 |doi-access=free |hdl=10261/235467 |hdl-access=free }}</ref>