title: Ammonia excretion in the marine polychaete Eurythoe complanata (Annelida).
abstract: Ammonia is a toxic waste product from protein metabolism and needs to be either converted into less toxic molecules or, in the case of fish and aquatic invertebrates, excreted directly as is. In contrast to fish, very little is known regarding the ammonia excretion mechanism and the participating excretory organs in marine invertebrates. In the current study, ammonia excretion in the marine burrowing polychaete Eurythoe complanata was investigated. As a potential site for excretion, the 100-200 µm long, 30-50 µm wide and up to 25 µm thick dentrically branched, well ventilated and vascularized branchiae (gills) were identified. In comparison to the main body, the branchiae showed considerably higher mRNA expression levels of Na+/K+-ATPase, V-type H+-ATPase, cytoplasmic carbonic anhydrase (CA-2), a Rhesus-like protein, and three different ammonia transporters (AMTs). Experiments on the intact organism revealed that ammonia excretion did not occur via apical ammonia trapping, but was regulated by a basolateral localized V-type H+-ATPase, carbonic anhydrase and intracellular cAMP levels. Interestingly, the V-type H+-ATPase seems to play a role in ammonia retention. A 1 week exposure to 1 mmol l-1NH4Cl (HEA) did not cause a change in ammonia excretion rates, while the three branchial expressed AMTs showed a tendency to be down-regulated. This indicates a shift of function in the branchial ammonia excretion processes under these conditions.
authors.affiliation: University of Osnabrück, Fachbereich Biologie, Department of Zoology, Osnabrück 49069, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Thiel
authors.affiliation: University of Osnabrück, Fachbereich Biologie, Department of Zoology, Osnabrück 49069, Germany.
authors.forename: Maja
authors.initials: M
authors.lastname: Hugenschütt
authors.affiliation: University of Osnabrück, Fachbereich Biologie, Department of Zoology, Osnabrück 49069, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Meyer
authors.affiliation: University of Osnabrück, Fachbereich Biologie, Department of Zoology, Osnabrück 49069, Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Paululat
authors.affiliation: University of Manitoba, Department of Biological Sciences, Winnipeg, Manitoba, Canada.
authors.forename: Alex R
authors.initials: AR
authors.lastname: Quijada-Rodriguez
authors.affiliation: University of Osnabrück, Fachbereich Biologie, Department of Zoology, Osnabrück 49069, Germany.
authors.forename: Günter
authors.initials: G
authors.lastname: Purschke
authors.affiliation: University of Manitoba, Department of Biological Sciences, Winnipeg, Manitoba, Canada Dirk.Weihrauch@ad.umanitoba.ca.
authors.forename: Dirk
authors.identifier: 0000-0002-3218-9093
authors.initials: D
authors.lastname: Weihrauch
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D000845:Annelida / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D001692:Biological Transport; D024402:Carbonic Anhydrase II / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D000242:Cyclic AMP / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D005880:Gills / Q000378:metabolism* / Q000648:ultrastructure; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000032:analysis / Q000235:genetics / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D000641:Ammonia; D000242:Cyclic AMP; D025262:Vacuolar Proton-Translocating ATPases; D024402:Carbonic Anhydrase II; D000254:Sodium-Potassium-Exchanging ATPase
keywords: AMTs; Acid–base regulation; Gill morphology; HEA; V-ATPase; cAMP