The oxygen capacity of bloods from nineteen species of lizards representing eight genera and three families were determined. Mean values obtained for these species ranged from 7.7 to 12.6 vol %. Oxygen capacity was found to be uncorrelated with the extent of heat resistance characterizing the various species. Likewise no correlation was evident between oxygen capacity and the altitude at which the lizards had existed prior to study, whether the analysis was concerned with populations within a single species (Sceloporus jarrovi), species within a single genus (Sceloporus), or with the entire array of species studied. The values reported for this study fall within t'he general range previously established for reptiles by other authors. The upper portion of this range overlaps the lower portion of that for oxygen capacities of birds and mammals. This overlap suggests that the demands upon respiratory transport created with the intensification of metabolism in the evolution of homeothermy have been met primarily through such means as augmentation of cardiac output rather than through any major increase in the transport capacities of the blood. We have undertaken this study of oxygen capacity of lizard bloods as an initial step in the analysis of respiratory transport in this group. Bloods of nineteen species from southwestern United States, representing eight genera and three families have been analyzed. Acknowledgments. -We are extremely grateful to Dr. Mont A. Cazier, the Director of the Southwestern Research Station, for the numerous courtesies extended to us during our work in Arizona, and to Harvey F. Pough for the assistance rendered in the capture and maintenance of lizards. We also wish to thank Dr. Wilbur W. Mayhew of the University of Calilfornia at Riverside for supplying us with desert iguanas, Dipsosaurus dorsalis. This study was supported in part by grants from the National Science Foundation (G-2096 and G-9238) and from the Horace H. Rackham School of Graduate Studies, The University of Michigan. MATERIALS AND METHODS A majority of the lizards used in this study were obtained in extreme southeastern Arizona and southwestern New Mexico, within 25 miles of the Southwestern Research Station, near Portal, Arizona. Sceloporus poinsetti and Crotaphytus collaris were obtained in Hidalgo County, New Mexico. Sceloporus jarrovi, S. undulatus virgatus (designation of subspecies has been made only where two or more conspecific forms occur within the same county), S. clarki, Uta stansburiana, Holbrookia texana, Phrynosoma modestum, P. cornutum, P. douglassi, Cnemidophorus inornatus, C. sacki, and C. tigris, were obtained in Cochise County, Arizona. Lizards which could be approached closely were captured with a noose connected to the end of a trout pole. More wary animals were obtained by stunning them with a heavy rubber band Present address: Department of Zoology, Yale University.
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Nov 1, 1970
Stephen R Goldberg 
