Meeting Abstract
P2.82 Friday, Jan. 4 Osmoregulatory changes during metamorphosis and salinity exposure of juvenile sea lamprey (Petromyzon marinus L.) REIS-SANTOS, Patrick; WILSON, Jonathan M.; MCCORMICK, Stephen D.*; USGS, Conte Anadromous Fish Research Center, Turners Falls, MA USA and Laborat�rio de Ecofisiologia, Centro Interdiscplinar de Investiga��o Marinha e Ambiental (CIIMAR), Porto, Portugal ; Laborat�rio de Ecofisiologia, Centro Interdiscplinar de Investiga��o Marinha e Ambiental (CIIMAR), Porto, Portugal ; USGS, Conte Anadromous Fish Research Center, Turners Falls, MA USA mccormick@umext.umass.edu
Ammocoetes of the anadromous sea lamprey (Petromyzon marinus L.) spend many years in fresh water before metamorphosing and migrating to sea. Metamorphosis involves the radical transformation from a substrate dwelling filter feeding ammocoete into a free swimming parasitic feeder. In the present work we examine osmoregulatory differences between ammocoetes and transformers, and the effects of salinity acclimation (15 d) in juvenile lamprey before and during transformation. Ammocoetes did not survive in salinity > 25�, whereas survival in high salinity (> 25-35�) increased with increased degree of metamorphosis in transformers. Plasma [Na+] and [Cl-] of ammocoetes in fresh water was lower than transformers and increased markedly at 10�. In transformers, plasma ions only increased at high salinity (>25�). Branchial Na+,K+-ATPase levels were ~10-fold higher in transformer 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 chloride cells in the interlamellar spaces. H+-ATPase (B subunit) immunoreactivity was localized to a separate cell type in a similar pattern as carbonic anhydrase. The results indicate that as with smolting salmonids, branchial Na+,K+-ATPase and chloride cells increase in transforming lamprey just prior to downstream migration and result in increased salinity tolerance.
