Carol Beuchat

Institute of Canine Biology

Augmenting the genetic diversity of small, inbred populations by the introduction of new individuals is often termed “genetic rescue“. An example is the Norwegian Lundehund, a small spitz dog with inbreeding-related health problems that is being crossed with three Nordic breeds, including the Norwegian Buhund. Conservation breeding decisions for th...

La degradación bacteriana de compuestos urinarios que contienen nitrógeno ha sido documentada en los ciegos de varias especies de aves herbívoras y omnívoras, y la absorción de los productos de esa degradación en los ciegos se ha documentado en gallinas. Este reciclaje de nitrógeno podría tener un papel importante en el balance de este elemento, es...

Degradation of urinary nitrogen-containing compounds by bacteria in the ceca of birds occurs in a number of herbivorous and omnivorous species, and cecal absorption of the products of that degradation has been reported in chickens. This recycling of nitrogen may play an important role in nitrogen balance, especially in those species with low dietar...

Little is known about the cellular mechanisms involved in the tolerance of deep-diving marine mammals to hydrostatic pressures that cause serious pathologies when experienced by other mammals. We compared fatty-acid composition, cholesterol content, and the effects of pressure on the molecular order of erythrocyte membranes from deep-, shallow-, an...

The Cape clawless otter (Aonyx capensis) is one of the few species of mammals that occur in both freshwater and marine habitats, and it therefore must be able to tolerate the high rates of water flux typical of aquatic animals as well as the desiccating effects of seawater. The clawless otter has paired, discrete multirenculate kidneys (total mass...

Hummingbirds have rates of water turnover that are among the highest of any bird, consuming up to five times their body mass in nectar each day. To determine if the processing of these extraordinary volumes of water is associated with structural specializations in the kidney, we examined the renal morphology of Anna's hummingbird (Calypte anna) usi...

We measured levels of glucose and glycated hemoglobin in the blood of three of the world's smallest nectarivorous birds, the Anna's (Calypte anna), Costa's (Calypte costae), and ruby-throated hummingbirds (Archilochus colubris). Plasma glucose levels of hummingbirds that were fasted overnight (17 mM) were higher than those in any mammal and are amo...

The kidneys of Anna's hummingbird (Calypte anna) differ in several significant ways from those of other birds that have been examined. The kidneys of this nectarivore contain very little medullary tissue; 90% of the total volume of the kidneys is cortical tissue, with medulla accounting for only an additional 2%. More than 99% of the nephrons are t...

In their report “A general model for the origin of allometric scaling laws in biology” ([4 Apr., p. 122][1]), Geoffrey B. West et al. explore the ubiquity of quarter-power scaling relationships in biology. They ([p. 122][2]) propose that a common mechanism underlies these laws: Living things are

Hummingbirds at rest and during long flights such as migration meet their energy needs by the catabolism of fat, but to support short flights they rely entirely on oxidation of carbohydrates. The duration of short flights is limited by glucose and glycogen stores in muscle, liver, and blood, which have yet to be measured. We determined glucose leve...

Mammals with relatively long loops of Henle for their body size tend to have greater than average urinary concentrating ability, but the relationship between urine osmolality (Uosm) and absolute length of the loop of Henle (generally estimated as medullary thickness) is neither proportional nor direct. Uosm is independent of the thickness of the ou...

Body mass of migrant Rufous Hummingbirds (Selasphorus rufus) on refueling stopovers increased on average from 3.2 to 4.6 g over a period ranging from several days to 3 wk. In birds arriving with body masses below ≈3.5 g, the initial period of mass gain was very slow. This slow gain was not explained by energy costs associated with territory establi...

Osmometry is an important tool in the investigation of biological phenomena, and commercially available instruments for freezing point and vapor pressure osmometry can determine the osmolality of solutions quickly and inexpensively. However, accurate measurements of osmolality using these techniques require that the solutions have specific characte...

The ultrastructure of the urinary bladder in selected species of lizards, turtles, tortoises, toads, and frogs was examined using light, scanning electron, and transmission electron microscopy. In all lizards examined, ciliated cells were found on the luminal surface of the tubular stalk that attaches the bladder to the cloaca but were absent in th...

The hummingbird's high metabolism requires efficient extraction of energy and nutrients from a dilute food source that is passing rapidly through the gastrointestinal (GI) tract. The ability of the hummingbird to efficiently process and excrete such large volumes of water must surely entail structural or functional specializations of the kidney and...

Metabolic rates of gravid females of the viviparous lizard Sceloporus jarrovi are higher than those of nonreproductive lizards: the allometric relationship between oxygen consumption and body mass in gravid females () has a statistically equivalent slope but a significantly higher intercept than that for males (). The elevated metabolism of females...

Currently accepted theories of the urine concentrating mechanism of the mammalian kidney predict that concentrating ability should increase with increasing length of the loop of Henle. However, larger mammals have longer nephrons than do smaller ones, yet concentrating ability declines with increasing body mass (M, in kg) as M-0.097. Greenwald & St...

B. H. Blake (Comp. Biochem. Physiol. A Comp. Physiol. 58: 413-419, 1977.) and W. A. Calder and E. J. Braun (Am. J. Physiol. 244 (Regulatory Integrative Comp. Physiol. 13): R601-R606, 1983.) have predicted that urine concentrating ability of mammals should decline with increasing body mass (M, in kg) as M-0.08. Edwards (29), on the other hand, specu...

The frequency of activity of the viviparous iguanid lizard Sceloporus jarrovi in a high altitude (2895 m) population was determined by hourly censuses of visible lizards. Any given lizard was seen an average of six days out of seven, and within days activity did not vary with either age or sex of the lizard. Patterns of lizard activity throughout t...

In reptiles, there are two pairs of kidneys at birth: the mesonephros and the metanephros. The metanephric kidney in reptiles, as in all amniote vertebrates, is retained as the functional kidney in adults. However, the reptilian mesonephros does not degenerate until after birth, and its function during this time is unknown. In neonates of the iguan...

1.1.The length of geslation of the viviparous lizard Sceloporus jarrovi is strongly dependent upon the body temperature of the pregnant female.2.2.Significantly more abnormal or dead offsping were born of pregnant females maintained at constant temperatures of 26, 36 and 38°C than in the control group that was allowed to behaviourally thermoregulat...

Pregnant females of the viviparous lizard species Sceloporus jarrovi regulate their body temperatures at a lower level than do males or nonpregnant females. It has been suggested that such a shift in preferred body temperature during pregnancy reflects the presence of divergent optimal temperatures for the female and for development of her young; a...

Both male and female Sceloporus jarrovi thermoregulate on every day during the summer when weather is suitable for lizard activity. Pregnant females, however, regulate a lower body temperature (x̄ 32.0 C) than do males or post-parturient females (x̄ 34.5 C) and, using the standard deviation about the mean as a measure of precision, also thermoregul...

Neonatal lizards of the viviparous species Sceloporus jarrovi possess at birth a urinary bladder that contains a large amount (14% of body mass at birth) of very dilute (36 mosm/kg) urine. After birth, no additional urine is added to the bladder, and the fluid it contains declines in volume and increases in osmotic concentration as the bladder dege...

The response to simultaneous temperature and dehydration stress was examined in three species of Puerto Rican frogs.Eleutherodactylus antillensis is found primarily in hot, arid grasslands at low altitudes.Eleutherodactylus portoricensis is restricted to cool, forested montane habitats above 300 m.Eleutherodactylus coqui occurs in both the lowlands...

The metabolic responses to graded levels of exercise were determined for three species of anuran amphibians (Bufo americanus, Hyla crucifer, and Rana sylvatica). Both oxygen consumption () and lactate production were measured at low, moderate, and high levels of mechanically stimfilated activity. Significant elevations in whole-body lactate content...

The viviparous Brazilian scincid lizard Mabuya heathi exhibits a suite of reproductive specializations widely believed to be confined to the eutherian mammals. This skink ovulates the smallest known reptilian egg ( approximately 1.0 mm in diameter). Placental transport accounts for >99% of the dry mass of the periparturient fetus, representing a de...

Reptiles are ectotherms; that is, they depend on external sources of heat to maintain their body temperature. Body temperature is regulated behaviorally rather than metabolically, primarily via habitat choice (sun vs. shade), orientation to thermal energy sources, and posture. Many of the processes involved in a reptile’s ability to procure, proces...

Typescript (photocopy) Thesis (Ph. D.)--Cornell University, May, 1982. Bibliography: leaves 153-165.

Anna (Calypte anna) and rufous (Selasphorus rufus) hummingbirds exhibited regular diurnal changes in body mass, locomotor activity (flight time and frequency), and feeding activity (frequency and consumption) at ambient temperatures () from 38 to -1 C. Body mass of both species increased gradually throughout the day and amounted to increases of as...