needs to suddenly swim very fast to catch a mayfly for dinner The vigorous swimming will cause its muscles to release large amounts of lactic acid into poorly buffered blood; this can severely disturb the blood's acid-base balance and thus impede the contraction of the trout's swimming muscles before it has captured its prey, One adaptation that helps fish solve this dilemma is that their muscles consist of two forms red muscle that is primarily oxidative and white muscle that is primarily glycolytic. The red muscle can be activated dur- ing slow swimming and the white muscle during fast swim- ming to avoid predators or capture prey. he graph presents the results of an experiment designed to explore how a trout solves this dilemma. In the experiment, a trout was made to swim vigorously for 15 minutes in a laboratory tank, then allowed a day's recovery. The lactic acid concentration in its blood was monitored periodically during swimming and recovery phases. How Do Swimming Fish Avoid Low Blood Ph? onuin DAnimals that live in oxygen-poor environments, like worms Iiving in the oxygen-free mud at the bottom of lakes, are not able to obtain energy from cellular respiration. Their cells lack the oxygen needed to act as a final electron acceptor for electron transport. Instead, these animals rely on glycolysis to obtain ATP and on regenerating NAD by reducing pyru- vate to lactic acid. Although the energy yield is much lower, this fermentative metabolism does not require oxygen. Even when oxygen is plentiful, the muscles of an active animal may use available oxygen, and so, be forced to rely on gly- colysis temporarily to generate the ATP for continued 1 contraction. s baisnThis presents a particular problem for fish. Fish blood ori is much lower in carbon dioxide than yours is, and as a con- 2sequence, the amount of sodium bicarbonate acting as a buf- vol fer in fish blood is also quite low. Consider a trout, which Analysis 160 BU3 CC 10 Mesdin 1. Applying Concepts a. Variable. What is the dependent variable? b. Recording data. Lactic acid levels are presented for both swimming and recovery periods. In what time units are the swimming data presented? The How Lactic Acid Levels Change After Exercise 18 Trout 1601 EYol TTZ pollw bos matodenm Zo Dnool avul An recovery data? 14- 2. Interpreting Data a. What is the effect of exercise on the level of lactic acid in the trout's blood? 12- TSTOMO HEAIREN b. Does the level of lactic acid change after exercise stops? How? 3. Making Inferences About how much of the total lactic acid created by vigorous swimming is released after this exercise stops? (HINT: Replot all points to the same scale on the X-axis and compare the areas under the curve.) 10- enouto 8 mallon P81 d 90-9 pilpe 4- 2 4. Drawing Conclusions Is this result consistent with the hypothesis that fish maintain blood pH levels by delaying the release of lactic acid from muscles? Why might this be beneficial to the fish? 0 5 10 15 2 468 10 12 14 16 18 20 22 24 Exercise (minutes) Recovery time (hours) eoitabixo 8 S ulA Duare Rover US. Fish and Wildife Service. 152 Part I Blology of the Cell ubu nalysis Relative lactic acid levels in blood Co