Biomedical subjects
F H Pough
Publications and source records attributed to F H Pough.
Diploid and tetraploid grey treefrogs (Hyla chrysoscelis and Hyla versicolor) have similar metabolic rates.
We measured oxygen consumption of the diploid frog Hyla chrysoscelis and its recently evolved tetraploid cryptic species Hyla versicolor at rest and during forced locomotory exercise. We also measured whole-body lactic acid concentrations of individuals of the two species at rest and following 4 min of exercise. Contrary to predictions based on tissue-culture experiments, rates of organismal metabolism are not different in this diploid/tetraploid species pair: the diploid and tetraploid species did not differ in rates of oxygen consumption at rest or during exercise. Furthermore, whole-body lactate concentrations of frogs at rest and following forced locomotion were the same in the diploid and tetraploid species. For these species, polyploidy does not appear to be associated with lower maintenance costs at the level of the organism. However, polyploidy also does not appear to have metabolic consequences that would limit the behavioral or ecological repertoire of an anuran.
Control of arterial pressure in aquatic sea snakes.
Cardiovascular responses to head-up tilt, acutely graded hemorrhage, and pharmacologic stimulation by principal autonomic drugs were studied in four species of marine snakes, principally Aipysurus laevis (family Hydrophiidae). Arterial pressure varied inversely with tilt angle and blood volume deficit in conscious snakes outside of water, indicating that physiological regulation was poor or lacking. Calculated arterial pressures at head level typically diminished to zero in A. laevis tilted to angles greater than or equal to 30 degrees. Arterial pressure (corrected for external water pressure) did not change when these snakes were tilted in seawater. Changes of arterial pressure induced by tilt, blood loss, or autonomic drugs elicited reflex adjustments in heart activity, but the magnitude of these responses was less than that observed in terrestrial species of snake. It is concluded that baroreflexes are present but comparatively ineffective in sea snakes. Snakes tolerated large losses of blood volume, and extravascular fluids were absorbed into the circulation during hemorrhage; both hemorrhage and estimated hemodilution volumes exceeded 100% of the initial blood volume in Acalyptophis peronii. Thus, in marine snakes major fluid shifts between nonvascular and vascular compartments significantly compensate hypovolemia but, because of minor autonomic adjustments, do not result in a well-regulated arterial pressure.
Internal fertilization in an oviparous frog.
Eleutherodactylus coqui, an oviparous frog, undergoes internal fertilization. If this mode of fertilization occurs in other species of anurans, interpretations of anuran reproductive strategies based on the assumption of external fertilization must be reviewed.
The effect of rattlesnake venom on digestion of prey.
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Melanin deposits associated with the venom glands of snakes.
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Ontogenetic change in molecular and functional properties of blood of garter snakes, Thamnophis sirtalis.
At birth the blood of garter snakes (Thamnophis sirtalis) has high oxygen affinity (P50 at 25 degrees C and pH 7.2 = 21 mm Hg), low hematocrit (14%), and a high proportion of inactive hemoglobin (44%). Growth of the snakes is accompanied by a steady decrease in oxygen affinity (P50 = 44 mm Hg in adults), increased hematocrit (to 44%), and decreased inactive hemoglobin (to 3%). These adult values are reached in the second or third year of a snake's life. There is a continuous change in the electrophoretically separable hemoglobin fractions during this period, but there is no ontogenetic change in the oxygen affinity of phosphate-stripped hemoglobin in solution. Organic triphosphates do not fully explain the ontogenetic change in blood oxygen affinity. Similar ontogenetic changes in blood oxygen affinity were found in two other species of snakes. The unusual morphology of snake lungs and consequent changes in pulmonary pO2 and pCO2 during ontogeny may be the basis for the unusual relationship between body size and blood oxygen affinity in snakes.
Acid precipitation and embryonic mortality of spotted salamanders, Ambystoma maculatum.
Spotted salamanders breed in temporary pools formed in early spring by melted snow and rain. Many of these pools reflect the low pH of precipitation in the northeastern United States. Egg mortality is low (less than 1 percent) in pools near neutrality, but high (greater than 60 percent) in pools more acid than pH 6. Developmental anomalies and the embryonic stage at which death occurs are the same in field situations as at corresponding pH's in laboratory experiments.
A physical basis for head-body temperature differences in reptiles.
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Geographic variation of blood proteins and the systematics of kingsnakes (Lampropeltis getulus).
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Temperatuer selection by the red-backed salamander, Plethodon c. cinereus (Green) (Caudata: Plethodontidae).
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Natural daily temperature acclimation of eastern red efts, Notophthalmus v. viridescens (Rafinesque) (Amphibia: Caudata).
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Theoretical investigations of automimicry: multiple trial learning and the palatability spectrum.
We previously explored automimicry assuming that a species of prey was so unpalatable as to promote conditioned avoidance for a period of time after a predator encountered a single individual (Case 1). In this paper, we assume that the prey is less noxious and that two encounters are required. Case 2 allows the two encounters with unpalatables to be separated by any number of palatables, while in Case 3 the predator must encounter two unpalatables, consecutively.The general relationships in the three cases are similar, but the automimetic advantage is reduced moderately in Case 2 and greatly in Case 3. To attain the same automimetic advantage as in Case 1 requires an increase in the proportion of unpalatables, or in the induced rejection period, or both. Consequently, selection will tend to increase the unpalatability so that Cases 2 and 3 converge to Case 1.Species that are uniformly and highly unpalatable can afford to be more dispersed than automimetic species. Case-2 and -3 automimetic species will benefit greatly from gregariousness, while in Case-1 automimicry situations this is less important.
Theoretical investigations of automimicry, I. Single trial learning.
The theory of automimicry is explored mathematically on the assumption that predators can learn to avoid noxious prey by sight for some finite period after a single noxious experience. Automimetic advantage is an inevitable consequence of the evolution of an unpalatability dimorphism. An established automimetic situation is analogous to an established perfect Batesian mimicry situation, although the evolutionary bases of the two phenomena are different. In both situations, the mimetic advantage depends upon the proportion of unpalatable prey, the memory span of the predators, and the abundance of the prey relative to the predators. Automimetic advantage is maximal when the prey are neither too common nor too rare. Remarkably low proportions of unpalatable prey can confer very substantial immunity to the population. A surprising prediction of the model is that the evolution of unpalatability will not occur in rare prey species unless they first become Batesian mimics. This in turn could lead to the evolution of mimicry complexes containing many species forming a whole spectrum of unpalatability.