Physiological cost of pregnancy in a viviparous lizard (Sceloporus jarrovi)

✍ Scribed by Demarco, Vincent ;Guillette, Louis J.

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 768 KB
• Volume: 262
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402620404

✦ Synopsis

Abstract

The V̇o~2~ (standard metabolic rate; cc · h^−1^) of pregnant Sceloporus jarrovi increases to a maximum near term. Immediately following parturition, V̇o~2~ decreases sharply. Approximately 93.6% of the V̇o~2~ of late pregnant S. jarrovi is due to litter and non‐reproductive female V̇o~2~. The difference between measures of the V̇o~2~ of late pregnant lizards and late pregnant V̇o~2~ estimated by summing litter and nonreproductive V̇o~2~ (6.4%) represents the physiological cost of maintaining a litter. This estimate of the physiological cost of pregnancy in S. jarrovi is similar to that reported for mammals; however, it is lower than other estimates of the cost of pregnancy in reptiles. Estimates of litter metabolism were obtained by measuring maximum embryo metabolism, using an in vitro technique and multiplying embryo V̇o~2~ by litter size. These results suggest that others have overestimated the physiological cost of pregnancy in reptiles because maximum litter V̇o~2~ has been underestimated. Others have suggested that viviparity is an expensive mode of reproduction because the physiological cost of supporting a litter is an important component of an individual's reproductive effort. Data presented here support the alternative hypotheses that the cost of supporting a litter is not high and constitutes a small fraction of the energy apportioned into reproduction. © 1992 Wiley‐Liss, Inc.