title: Ionoregulatory changes during metamorphosis and salinity exposure of juvenile sea lamprey (Petromyzon marinus L.).
abstract: Ammocoetes of the anadromous sea lamprey Petromyzon marinus L. spend many years in freshwater before metamorphosing and migrating to sea. Metamorphosis involves the radical transformation from a substrate-dwelling, filter feeder into a free-swimming, parasitic feeder. In the present work we examined osmoregulatory differences between ammocoetes and transformers (metamorphic juveniles), and the effects of salinity acclimation. We measured the expression of key ion-transporting proteins [Na(+)/K(+)-ATPase, vacuolar (V)-type H(+)-ATPase and carbonic anhydrase (CA)] as well as a number of relevant blood parameters (hematocrit, [Na(+)] and [Cl(-)]). In addition, immunofluorescence microscopy was used to identify and characterize the distributions of Na(+)/K(+)-ATPase, V-type H(+)-ATPase and CA immunoreactive cells in the gill. Ammocoetes did not survive in the experiments with salinities greater than 10 per thousand, whereas survival in high salinity (> or =25-35 per thousand) increased with increased degree of metamorphosis in transformers. Plasma [Na(+)] and [Cl(-)] of ammocoetes in freshwater was lower than transformers and increased markedly at 10 per thousand. In transformers, plasma ions increased only at high salinity (>25 per thousand). Branchial Na(+)/K(+)-ATPase levels were approximately tenfold higher in transformers compared to ammocoetes and salinity did not affect expression in either group. However, branchial H(+)-ATPase expression showed a negative correlation with salinity in both groups. Na(+)/K(+)-ATPase immunoreactivity was strongest in transformers and associated with clusters of cells in the interlamellar spaces. H(+)-ATPase (B subunit) immunoreactivity was localized to epithelial cells not expressing high Na(+)/K(+)-ATPase immunoreactivity and having a similar tissue distribution as carbonic anhydrase. The results indicate that branchial Na(+)/K(+)-ATPase and salinity tolerance increase in metamorphosing lampreys, and that branchial H(+)-ATPase is downregulated by salinity.
authors.affiliation: Centro Interdiscplinar de Investigação Marinha e Ambiental, Rua dos Bragas 289, 4050-123 Porto, Portugal.
authors.forename: Patrick
authors.initials: P
authors.lastname: Reis-Santos
authors.forename: Stephen D
authors.initials: SD
authors.lastname: McCormick
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Wilson
mesh_terms: D000064:Acclimatization; D000818:Animals; D002256:Carbonic Anhydrases / Q000378:metabolism; D002712:Chlorides / Q000097:blood; D005618:Fresh Water; D005880:Gills / Q000378:metabolism; D007150:Immunohistochemistry; D017136:Ion Transport; D008675:Metamorphosis, Biological; D048428:Petromyzon / Q000254:growth & development* / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000378:metabolism; D054712:Salinity; D012623:Seawater; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014882:Water-Electrolyte Balance
chemical_list: D002712:Chlorides; D012964:Sodium; D006180:Proton-Translocating ATPases; D002256:Carbonic Anhydrases; D000254:Sodium-Potassium-Exchanging ATPase