I love fishing! I just returned from a weekend fishing trip with my family where we caught these beautiful trout (see photo).
Speaking of fish, I just finished listening to a LifeLines podcast from The American Physiological Society in which Barbara Block from Stanford University discussed her research on bluefin tuna.
Dr. Block uses electronic tags implanted in fish to record information on their location, depth, body temperature, heart rate, food intake, etc. These tags allow her to study the physiology of the animals in their natural environment. Audio clip.
Her research team has tracked these fish as they swim through the ocean to their feeding and breeding grounds. In this podcast, she discusses the bluefin tuna, which is the largest, warmest, farthest swimming, and deepest diving tuna. For researchers, their athletic prowess makes them interesting models in which to examine how the heart has evolved to supply oxygen during endurance exercise while at the same time remaining resistant to cold temperatures. Audio clip.
The cardiac function of fish is also studied in rainbow trout, like the ones my family caught on our recent trip (with the pink stripe in the picture). Besides being a very tasty fish, Drs. Battiprolu, Goddard, and Rodnick from Idaho State University have found that cardiac function differs in male and female rainbow trout under working conditions. When they stimulated hearts with a drug that activates pyruvate dehydrogenase, an enzyme involved in carbohydrate oxidation, they found that the hearts of female rainbow trout had better performance and reduced release of lactate. Male rainbow trout in contrast, have higher levels of citrate, an enzyme that inhibits glycolysis, and larger epicardium to endocardium ratios. To read more, visit APS.org.
On my last fishing trip, we arrived at our favorite fishing lake only to discover that it was still frozen over. Sadly, my attempt at ice fishing was rather unsuccessful, but I have always wondered how fish could survive under hypoxic conditions when the oxygen content becomes limited. Drs. Vornanen and Paajanen of the University of Joensuu in Finland examined this very question in Crucian carp, a cousin to the much beloved goldfish. They found that decreasing water temperatures trigger a physiological change in these fish to begin storing glycogen in their brains to survive the low oxygen environment of ponds from February to April. At the same time, the carp slow down the energy metabolism of their brains allowing them to survive without oxygen. Being able to survive in this rather inhospitable environment helps to protect these fish from predators.
APS.org. If only my childhood pet goldfish could have used this tactic to survive the bath bubbles my mother accidentally spilled in its tank...poor Goldie.
the carp slow down the energy metabolism of their brains
Meaning what? Rates of protein synthesis? Ion pumping / membrane permeability? "Energy metabolism" is an effect, not a cause.
Specifically, although the number of sodium-potassium ATPase units in the brain of the carp remain constant throughout the year, the activity (catalytic rate) of the sodium-potassium pump is reduced in the winter as a result of the lower temperatures. Moreover, these winter-acclimatized carp store excessive glycogen in their brains which fuels the sodium-potassium pump through the ATP that is generated from glycolysis. The authors conclude this translates into roughly 16 hours of glycogen supplied energy in the brain of the winter-acclimatized carp compared to only 8 minutes for the summer-acclimatized carp.
I saw Dr. Block give the Canon lecture at EB a few years ago. It was my favorite lecture ever. She really is one of my scientific heroes.