The lability of blood volume and its relationship to locomotor activity was investigated in two species of snakes Elaphe obsoleta, Say and Crotalus viridis, Rafinesque. Repetitive measurements of blood volume, determined from changes in the specific activity of circulating 51Cr-labelled erythrocytes, indicated that 15 min of locomotor activity reduced blood volume by 21% due to filtration of plasma from capillaries. This magnitude of plasma translocation exceeds that measured in exercising mammals by factors of 2 to 7, depending on the intensity and duration of muscular activity. Activity produced changes in arterial blood pressure, heart rate and haematocrit that were proportionately similar in both species, increasing approximately 57, 85 and 25%, respectively, above resting values. Arterial infusion of norepinephrine increased arterial pressure by more than 100% and reduced blood volumes 8.6 and 17.0% in Elaphe and Crotalus, respectively. These data demonstrate that blood volume varies substantially in relation to activity or the hypertensive state of these reptiles. Thus care must be employed in interpreting or comparing reported measurements of blood volume in these and probably other vertebrates.
In the field: an interview with Martha Muñoz
Martha Muñoz is an Assistant Professor at Yale University, investigating the evolutionary biology of anole lizards and lungless salamanders. In our new Conversation, she talks about her fieldwork in Indonesia, Costa Rica, the Dominican Republic and the Appalachian Mountains, including a death-defying dash to the top of a mountain through an approaching hurricane.
Graham Scott in conversation with Big Biology
Graham Scott talks to Big Biology about the oxygen cascade in mice living on mountaintops, extreme environments for such small organisms. In this JEB-sponsored episode, they discuss the concept of symmorphosis and the evolution of the oxygen cascade.
Trap-jaw ants coordinate tendon and exoskeleton for perfect mandible arc
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Trap-jaw ants run the risk of tearing themselves apart when they fire off their mandibles, but Greg Sutton & co have discovered that the ants simultaneously push and pull the mandibles using energy stored in a head tendon and their exoskeleton to drive the jaws in a perfect arc.
Hearing without a tympanic ear
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In their Review, Grace Capshaw, Jakob Christensen-Dalsgaard and Catherine Carr explore the mechanisms of hearing in extant atympanate vertebrates and the implications for the early evolution of tympanate hearing.
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