Cardiorespiratory upregulation during seawater acclimation in rainbow trout: effects on gastrointestinal perfusion and postprandial responses

• Increased gastrointestinal blood flow is essential for euryhaline fishes to maintain osmotic homeostasis during the initial phase of a transition from freshwater to seawater. However, the cardiorespiratory responses and hemodynamic changes required for a successful long-term transition to seawater remain largely unknown. In the present study, we simultaneously measured oxygen consumption rate ((M)over dot(O2)), cardiac output (CO), heart rate (HR), and gastrointestinal blood flow (GBF) in rainbow trout (Oncorhynchus mykiss) acclimated to either freshwater or seawater for at least 6 wk. Seawater-acclimated trout displayed significantly elevated ((M)over dot(O2)) (day: 18%, night: 19%), CO (day: 22%, night: 48%), and GBF (day: 96%, night: 147%), demonstrating that an overall cardiorespiratory upregulation occurs during seawater acclimation. The elevated GBF was achieved via a combination of increased CO, mediated through elevated stroke volume (SV), and a redistribution of blood flow to the gastrointestinal tract. Interestingly, virtually all of the increase in CO of seawater-acclimated trout was directed to the gastrointestinal tract. Although unfed seawater-acclimated trout displayed substantially elevated cardiorespiratory activity, the ingestion of a meal resulted in a similar specific dynamic action (SDA) and postprandial GBF response as in freshwater-acclimated fish. This indicates that the capacity for the transportation of absorbed nutrients, gastrointestinal tissue oxygen delivery, and acid-base regulation is maintained during digestion in seawater. The novel findings presented in this study clearly demonstrate that euryhaline fish upregulate cardiovascular function when in seawater, while retaining sufficient capacity for the metabolic and cardiovascular changes associated with the postprandial response.

Ämnesord

NATURVETENSKAP  -- Biologi -- Zoologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Zoology (hsv//eng)

Nyckelord

saltwater

gut blood flow

cardiovascular

feeding

metabolic rate

ACID-BASE REGULATION

GUT BLOOD-FLOW

ONCORHYNCHUS-MYKISS

FRESH-WATER

OXYGEN-CONSUMPTION

SALMO-GAIRDNERI

ALKALINE TIDE

BICARBONATE

SECRETION

METABOLIC-RESPONSE

DYNAMIC ACTION

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)