Modeling the Metabolic Energetics of Brief and Intermittent Locomotion in Lizards and Rodents

SUMMARYCallinectes sapidus (Rathbun), the Atlantic blue crab, commonly harbors low to moderate amounts of bacteria in hemolymph and other tissues. These bacteria are typically dominated by Vibrio spp., which are known to cause mortality in the blue crab. The dose-dependent lethality of an isolate of Vibrio campbellii was determined in crabs; the mean 48h LD 50 (half-maximal lethal dose) was 6.2ϫ10 5 colony forming unitsg -1 crab. Injection of a sublethal dose of V. campbellii into the hemolymph of the crab resulted in a rapid and large depression (30-42%) of metabolic rate, which persisted for 24h. Because gills are an organ of immune function as well as respiration, we were interested in how bacteria injected into the crab would affect the energetic costs associated with walking. Overall metabolism (aerobic and anaerobic) more than doubled in crabs walking for 30min at 8mmin -1 . The metabolic depression resulting from bacterial injection persisted throughout the exercise period and patterns of phosphagen and adenylate consumption within walking leg muscle were not affected by treatment. The ability of crabs to supply required energy for walking is largely unaffected by exposure to Vibrio; however, Vibrio-injected crabs are less aerobic while doing so. This depressed metabolic condition in response to bacteria, present during moderate activity, could be a passive result of mounting an immune response or may indicate an actively regulated metabolic depression. A compromised metabolism can affect the performance of daily activities, such as feeding and predator avoidance or affect the ability to cope with environmental stressors, such as hypoxia.

Section: Discussionsupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Energy metabolism and metabolic depression during exercise inCallinectes sapidus, the Atlantic blue crab: effects of the bacterial pathogenVibrio campbellii

Thibodeaux

Burnett

2009

“…In our study, the subjects did not appear to utilize speeds that minimized their energetic costs. Our data agree with those from other studies that indicate that small mammals do not move efficiently, as a rule; they exhibit poor EMA, use relatively high stride frequencies and tend to move in costly, intermittent bouts (Biewener, 1989;Fischer, 1994;Gleeson and Hancock, 2001;Hodson-Tole and Wakeling, 2010). Rather than optimize efficiency, small mammals seem to optimize maneuverability and acceleration (Fischer, 1994).…”

Section: Cost Of Transportsupporting

confidence: 91%

Crouching to fit in: the energetic cost of locomotion in tunnels

Hörner

Hanna

Biknevicius

2016

Animals that are specialized for a particular habitat or mode of locomotion often demonstrate locomotor efficiency in a focal environment when compared to a generalist species. However, measurements of these focal habitats or behaviors are often difficult or impossible to do in the field. In this study, the energetics and kinematics of simulated tunnel locomotion by two unrelated semifossorial mammals, the ferret and degu, were analyzed using openflow respirometry and digital video. Animals were trained to move inside of normal (unconstrained, overground locomotion) and height-decreased (simulated tunnel, adjusted to tolerance limits for each species) Plexiglas chambers that were mounted flush onto a treadmill. Both absolute and relative tunnel performance differed between the species; ferrets tolerated a tunnel height that forced them to crouch at nearly 25% lower hip height than in an unconstrained condition, whereas degus would not perform on the treadmill past a ∼9% reduction in hip height. Both ferrets and degus exhibited significantly higher metabolic rates and cost of transport (CoT) values when moving in the tunnel condition relative to overground locomotion. When comparing CoT values across small (<10 kg) mammals, ferrets demonstrated a lower than predicted metabolic cost during both tunnel and terrestrial locomotion, whereas degus were very close to the line of best fit. Although tunnel locomotion requires a more striking change in posture for ferrets, ferrets are more efficient locomotors in both conditions than mammals of similar mass.

“…As a result, their reported running speeds are substantially greater than those recorded in this study, and represent what lizards can achieve during burst sprints involving brief, high accelerations. This is unsurprising, as it is well known that intermittent locomotion can increase peak locomotor performance, and is a common strategy employed during regular, undisturbed locomotion in nature (Weinstein and Full, 1998;Gleeson and Hancock, 2001;Weinstein, 2001). The findings in this study therefore address locomotor parameters that represent the performance capacity of sustained locomotion in these lizards.…”

Section: Kinematic Changes Associated With Tail Lossmentioning

confidence: 78%

Tail loss and narrow surfaces decrease locomotor stability in the arboreal green anole lizard (Anolis carolinensis)

Hsieh

2015

Tails play an important role in dynamic stabilization during falling and jumping in lizards. Yet tail autotomy (the voluntary loss of an appendage) is a common mechanism used for predator evasion in these animals. How tail autotomy has an impact on locomotor performance and stability remains poorly understood. The goal of this study was to determine how tail loss affects running kinematics and performance in the arboreal green anole lizard, Anolis carolinensis. Lizards were run along four surface widths (9.5 mm, 15.9 mm, 19.0 mm and flat), before and following 75% tail autotomy. Results indicate that when perturbed with changes in surface breadth and tail condition, surface breadth tends to have greater impacts on locomotor performance than tail loss. Furthermore, while tail loss does have a destabilizing effect during regular running in these lizards, its function during steady locomotion is minimal. Instead, the tail probably plays a more active role during dynamic maneuvers that require dramatic changes in whole body orientation or center of mass trajectories.