Effects of Salinity Challenge on Ion Regulation in Early and Late Upstream Migrating Sea Lamprey, Petromyzon marinus.

Abstract

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The sea lamprey, Petromyzon marinus, is an anadromous species in which the adults re-enter freshwater, and migrate upstream for terminal spawning. A reduction in salinity tolerance has been document in migrants although the underlying mechanisms have not been characterized. The aim of this study was to determine the capacity for marine osmoregulation in late, upstream migrants by characterizing the morphological and physiological effects of salinity challenge from a molecular perspective. For this two experiments were performed using early and late upstream migrants. Animals salinity limited was found to be 17.5‰ for late upstream migrants, thought some early migrants were able to perform at 24‰. A number of relevant blood and intestinal parameters were measured to assess ionoregulatory and biochemical changes as well as the expression of key ion-transport related proteins by immunoblotting (IB) [Na+/K+-ATPase (NKA), vacuolar-type H+-ATPase, carbonic anhydrase, and Na+:K+:2Cl-contransporter]. NKA activity was also measured, in addition to oxidative stress indicators. The Na+ and Cl- levels with plasma and intestinal fluid were quantified and it was found that in non performing animals these fluids approached environmental concentrations (osmoconforming and failure of drinking mechanism, respectively). A drop in hematocrit was also observed with plasma lactate indicating hemolytic anemia. Plasma [ALT], GST activity and [GSH] were used to assess oxidative damage to tissues. An increase in Na+/K+-ATPase activity in mid-intestine in late migrants and posterior intestine in early migrates showed a potentially adaptive ionoregulatory response to salinity increase. (FCT grant PTDC/MAR/98035/2008).

Keywords

• osmoregulation
• Spawning Migration
• osmotic stress
• Ionoregulation
• Seawater acclimation