Victor H. Hutchison

Relation of Body Size and Surface Area to Gas Exchange in Anurans

T HE skin, lungs, and buccal cavity may all serve as respiratory surfaces in adult terrestrial amphibians. The relative role of these respiratory surfaces has been shown to be an important consideration in the ecology, geographic distribution, and phylogenetic relationships of caudate amphibians (Whitford and Hutchison, 1963, 1965, 1966, 1967). Respiration in anurans has been reviewed by Foxon (1964). Information on the comparative importance of the various respiratory surfaces in anurans has been based primarily on the anatomical studies of vascularization of respiratory surfaces (Czopek, 1955a, 1955b; Czopek and Czopek, 1959; Bieniak and Watka, 1962). Physiological studies dealing with the role of these respiratory surfaces in anurans have been limited to the classical studies of Krogh (1904) and Dolk and Postma (1927) on the European frogs, Rana esculenta and R. tem-

Body Size and Metabolic Rate in Salamanders

W HEN the metabolic rates of large and small individuals of the same species or different species are compared, small animals are found to have the highest metabolic rate; that is, small organisms consume more oxygen per unit weight than large ones. Metabolism is generally more uniform when expressed as a power function of body weight. The relationship between body size and metabolic rate has been extensively reviewed by Kleiber (1947), Hemmingsen (1950, 1960) and Zeuten (1953). These authors state that the relationship between body size and metabolism is similar for homeotherms and

Gas Exchange in Salamanders

M EMBERS of the class Amphibia utilize every type of respiratory gas exchange known in the vertebrates-gills, lungs, skin, and buccopharyngeal mucosa-different species using them in various combinations. For example, the adults of most families of salamanders and frogs use skin, lung, and buccopharyngeal respiration, but the lungless salamanders of the family Plethodontidae use only buccopharyngeal and cutaneous gas exchange. Gills are common in the larval stages of most amphibians and cease to function at metamorphosis, but in some neotenic salamandrids and ambystomids gill respiration is retained in the adults. In aquatic, permanently larval Proteidae, such as Necturus maculosus, gills, skin, lungs, and buccopharyngeal mucosa may all be functional in respiration in sexually mature individuals (Noble, 1931). Thus, in their evolution the Amphibia have developed all the possible types of respiratory surfaces available to vertebrates. Since amphibians exhibit such a variety of mechanisms for respiratory exchange, a qualitative and quantitative knowledge of the relative roles of these respiratory surfaces in gas exchange in representatives of various families of am-

Thermoregulation in a Brooding Female Indian Python, Python molurus bivittatus

At varying environmental temperatures, measurements of body temperatures and gas exchange of a female Indian python (Python molurus bivittatus) show that during the brooding period this animal can regulate its body temperature by physiological means analogous to those in endotherms. Ambient temperatures below 33�C result in spasmodic contractions of the body musculature with a consequent increase in metabolism and body temperature.

Respiration and metabolism of embryonic vertebrates

Oxygen transfer in viviparous vertebrates is facilitated by the close proximity of fetal and maternal circulatory systems. Among the fishes, facilitation is accomplished by a remarkable diversity of maternal-fetal anatomical specializations. Maternal-fetal 02 transfer is further enhanced by a fetal blood which has a higher 02 affinity than that of the adult. The diversity of anatomical specializations suggests that there may be a similar variety of molecular specializations as well to ensure a relatively high fetal blood O2 affinity. Study of adult and fetal bloods of the seaperch, Embiotoca lateralis have shown that fetal blood has a higher O2 affinity than that of the adult. It appears that the E. lateralis fetus utilizes a different hemoglobin and a lower organic phosphate concentration to ensure this higher blood O2 affinity; a lower mean corpuscular hemoglobin concentration may contribute to the higher 02 affinity as well. A higher fetal than adult O2 affinity of whole blood exists in at least some sharks. The molecular basis for such affinity differences also appears to involve different fetal and adult hemoglobins; different intraerythrocytic organic phosphate concentrations may contribute as well. However, further studies are required to clarify the molecular basis of the facilitation of maternal-fetal 0, transfer in the fishes.

Energetics for Activity in the Diamondback Water Snake, Natrix rhombifera

The diamondback water snake, Natrix rhombifera, exhibited significant daily cycles of rate of oxygen consumption (

Acute adjustment of thermal tolerance in vertebrate ectotherms following exposure to critical thermal maxima

\dot{V}O_{2}

Pulmonary, branchial and cutaneous gas exchange in the mud puppy, Necturusmaculosus maculosus (Rafinesque)

) when acclimated at 15 and 35 C but not at 25 C. Routine activity followed the

Critical Thermal Tolerances and Heating and Cooling Rates of Lizards from Diverse Habitats

\dot{V}O_{2}

Glucose and lactate concentrations during activity in the leopard frog,Rana pipiens

cycles at 15 and 35 C but not at 25 C. Oxygen consumption and total body lactate production during 10 min forced activity showed a high dependence (65.8%-85.9%) on anaerobiosis at all temperatures. The oxygen debt at 25 C could account for all of the energy required for gluconeogenesis of all the lacta te removed during the period of a measurable oxygen debt, but lactate removal and gluconeogenesis continued beyond this time. Muscle lactate was highest and muscle glycogen lowest immediately after activity. Both had returned to resting concentrations by 3 h after activity, at which time blood and liver lactate concentrations were still high. The continued rise in blood glucose during recovery and the lack of any significant change in liver glycogen during either activity or recovery indicate a high dependence on gluconeogenesis to remove the lactate formed and to restore muscle glycogen. The strong dependence on anaerobiosis during activity may be an adaptation to a semiaquatic life-style.