William J. Mautz

Ontogenetic Changes in Diet, Field Metabolic Rate, and Water Flux in the Herbivorous Lizard Dipsosaurus dorsalis

Dietary energetics of Dipsosaurus dorsalis were studied to test the hypothesis that high mass-specific food energy requirements of small (3.5 g) hatchlings preclude herbivory in early life. This was not the case. Hatchlings were no less herbivorous than adults; arthropod prey constituted only 1% of the diet of both age classes. Field metabolic rate, water turnover, and feeding rate were measured in different seasons for separate age classes using doubly labeled water (H3H18O), and assimilation efficiency was measured for different age classes eating natural and exclusively arthropod (Tenebrio larvae) diets. Compared to spring vegetation, Tenebrio diets yielded 2.3 times the assimilable energy per g dry matter consumed, owing to higher energy content and greater assimilability of the arthropods. Assimilation efficiency for the natural autumn diet during a drought season declined to 0.29 in adult Dipsosaurus; however, hatchling lizards maintained an assimilation efficiency of 0.54 by specializing on flowers of Coldenia palmeri, which were too small for adults to harvest effectively. High mass-specific energy requirements associated with small body size did not impose a physiological limitation precluding herbivory in a lizard as small as hatchling Dipsosaurus. Hatchlings supported mass-specific energy expenditures more than double those of adults by processing vegetation at more than twice the mass-specific rates of adults. However, drought-related temporal variation in vegetative food quality can impose an ecological limitation on small herbivores. Among lizard species, specialist herbivores tend to be large and have herbivorous hatchlings, while small lizard species tend to be carnivorous. Ontogenetic shifts in the balance of the diet from carnivory at hatching toward herbivory at maturation is found among omnivorous species of intermediate adult size.

Breathing pattern and metabolic rate responses of rats exposed to ozone

Breathing pattern (frequency and tidal volume), minute ventilation (VE), oxygen consumption (MO2), and rectal temperature (TR) were measured from rats exposed to 0.8, 0.6, 0.4, and 0.2 ppm O3 to determine the relation between breathing pattern responses to O3 and metabolic rate. In 0.8 ppm O3, rapid-shallow breathing began at 60 min exposure while VE and MO2 declined beginning at 40 min. In comparison to clean air exposed animals, rats (n = 8) during the third hour of 0.8 ppm O3 exposure had a 27% increase in frequency, 35% decline in tidal volume, 20% decrease in VE, 24% decrease in MO2, and 1.3 degrees C decrease in TR. At lower O3 concentrations, responses were diminished in magnitude, and in rats exposed to 0.2 ppm O3, only MO2 was significantly decreased, irritant-induced depression of VE did not imply a state of hypoventilation or hypoxia because ventilation equivalent for O2 (VE/MO2) did not decline during O3 exposures. Body temperature and metabolic rate depression have not been observed during the development of rapid-shallow breathing in dogs or humans exposed to these low levels of O3, and the present observations in rats may reflect a more labile thermoregulatory physiology among rodents. Ventilatory and metabolic rate depression in response to irritant inhalation can be an effective pulmonary defense in rodents and other heterothermic mammals.

Population Densities of the Coquí, Eleutherodactylus coqui (Anura: Leptodactylidae) in Newly Invaded Hawaii and in Native Puerto Rico

Abstract Eleutherodactylus coqui was accidentally introduced to east Hawaii Island in the late 1980s and has since become established as scattered populations across the island. Mark-recapture study plots indicate that population size remains small for the first year after initial colonization. Plots in heavily forested areas where the Coquí has become well-established yield population estimates of frog density three times the estimates reported from native populations in Puerto Rico. Surveys of the Hilo area using sound pressure level meters found many loud chorusing populations producing sound pressure levels up to 73 dB suggesting that this frog will achieve high densities through broad areas of Hawaiian forest and towns. We suggest that the apparent lack of native or exotic predators in Hawaii and abundance of suitable retreat sites contribute to achievement of unusually high population densities of E. coqui in Hawaii compared with Puerto Rico.

Enhancement of ozone-induced lung injury by exercise.

Rats were exposed for up to 3.75 h to 0.20-0.80 ppm O3 under conditions of rest and treadmill exercise up to 30 m/min, 20% grade, to assess the importance of exposure duration, O3 concentration, and exercise on lung tissue injury. Focal lung parenchymal lesions increased in abundance and severity in response to the three variables; however, exercise was the most important. Lesion response to exercise was greater than that predicted by a simple proportion to estimated effective dose of O3. The results emphasize the importance of including exercise in assessment of possible adverse health effects of exposure to airborne pollutants.

Chronic inhalation exposure to ozone and nitric acid elevates stress-inducible heat shock protein 70 in the rat lung.

The ability of urban oxidant and acid air pollutants to induce heat shock proteins (HSPs) in the mammalian lung is not known. Such proteins are known to be correlated with environmental stress and pathophysiological conditions. In this study, stress-inducible HSP 70 was assessed by slot-blotting in rat lungs (N=10 per group) following inhalation exposures for 4 h per day, 3 days per week for 40 weeks to the following pollutants: (a) purified air;(b) 0.15 ppm ozone (O3);(c)50 micrograms/m3 nitric acid (HNO3); or(d) a combination of both 0.15 ppm O3 and 50 micrograms/m3 HNO3. At 24 h following the last exposure, samples from the right apical lobe of the lung were obtained for either slot-blotting or gel electrophoretic separation, subsequent protein immunoblotting, and chemiluminescence detection of HSP 70 levels. Experiments demonstrate that stress-inducible HSP 70 was present constitutively in the control lungs and was separable from the constitutive form of HSP 70. Slot-blotting analysis demonstrate that the O3 and HNO3 exposures alone produced significant elevations of HSP70. Specifically, either O3 or HNO3 alone significantly elevated lung stress-inducible HSP 70 levels by 277% and 221% respectively, above control levels. The group exposed to combined O3 and HNO3 showed a 177% elevation in lung stress-inducible HSP 70 that was significantly greater that the group inhaling purified air, but this effect was less than the effects of either pollutant component alone. Moreover, all exposure groups were significantly different from one another. These results indicate that stress-inducible HSP 70 in the rat lung is highly elevated after chronic inhalation exposures to both O3 and HNO3 when administered either alone or in combination within the range of urban ambient concentrations.

Evaporative water loss: humidity acclimation in Anolis carolinensis lizards

Anolis carolinensis lizards maintained for 7+ days in dry air ( 95% rh). Evaporation rates from skin isolated from lizards living in dry air were also less than half those from skin of lizards kept in humid air. These results indicate that A. carolinensis can improve its water balance status in desiccating conditions by reducing water loss via evaporation, and that reduction of cutaneous evaporation is an important component of this adjustment. The plasticity of evaporation rates of individual lizards in response to prior conditioning is large, and raises the question of whether the well-known correlation between evaporation rate and habitat aridity in reptiles reflects primarily inherited or acquired characteristics.

Parasite loss and introduced species: a comparison of the parasites of the Puerto Rican tree frog, (Eleutherodactylus coqui), in its native and introduced ranges

The Puerto Rican frog, Eleutherodactylus coqui has invaded Hawaii and reached densities far exceeding those in their native range. One possible explanation for the success of E. coqui in its introduced range is that it lost its co-evolved parasites in the process of the invasion. We compared the parasites of E. coqui in its native versus introduced range. We collected parasite data on 160 individual coqui frogs collected during January-April 2006 from eight populations in Puerto Rico and Hawaii. Puerto Rican coqui frogs had higher species richness of parasites than Hawaiian coqui frogs. Parasite prevalence and intensity were significantly higher in Hawaii, however this was likely a product of the life history of the dominant parasite and its minimal harm to the host. This suggests that the scarcity of parasites may be a factor contributing to the success of Eleutherodactylus coqui in Hawaii.

Effects of exercise exposure on toxic interactions between inhaled oxidant and aldehyde air pollutants

Respiratory tract injury resulting from inhalation of mixtures of ozone (O3) and nitrogen dioxide (NO2) and of O3 and formaldehyde (HCHO) was studied in Sprague-Dawley rats under exposure conditions of rest and exercise. Focal inflammatory injury induced in lung parenchyma by O3 exposure was measured morphometrically and HCHO injury to the nasal respiratory epithelium was measured by cell turnover using tritium-labeled thymidine. Mixtures of O3 (0.35 or 0.6 ppm) with NO2 (respectively 0.6 or 2.5 ppm) doubled the level of lung injury produced by O3 alone in resting exposures to the higher concentrations and in exercising exposures to the lower concentrations. Formaldehyde (10 ppm) mixed with O3 (0.6 ppm) resulted in reduced lung injury compared to O3 alone in resting exposures, but exercise exposure to the mixture did not show an antagonistic interaction. Nasal epithelial injury from HCHO exposure was enhanced when O3 was present in a mixture. Mixtures of O3 and NO2 at high and low concentrations formed respectively 0.73 and 0.02 ppm nitric acid (HNO3) vapor. Chemical interactions among the oxidants, HNO3, and other reaction products (N2O5 and nitrate radical) and lung tissue may be the basis for the O3-NO2 synergism. Increased dose and dose rate associated with exercise exposure may explain the presence of synergistic interaction at lower concentrations than observed in resting exposure. No oxidation products were detected in O3-HCHO mixtures, and the antagonistic interaction observed in lung tissue during resting exposure may result from irritant breathing pattern interactions.

Cellular and immunologic injury with PM-10 inhalation

AbstractAirborne particles Jess than 10 μsm (PM-10) in mass median aerodynamic diameter (MMAD) are associated with adverse effects on human health including chronic lung diseases and mortality, but the mechanisms by which these particles might cause or aggravate diseases are not specifically known. PM-10 represents a complex mixture, both in terms of size and chemical composition, and it contains both aqueous-media soluble and insoluble particles. Furthermore, the ambient aerosol composition varies markedly in different locations and at different times in the same location. To test the effects of PM-10 on pulmonary defenses in relation to specific cell targets, barrier-reared Sprague-Dawley rats were exposed to purified air (control), to two important constituents of the fine-particle < 1 μm MMAD) fraction of PM-10–ammonium sulfate [(NH4)2SO42-] (20 or 70 μg SO42- m−3, 0.2 μm MMAD) and ammonium nitrate [NH4NO31 (90 or 350 NO3 μg m −3, 0.6 μm MMAD). Rats were also exposed to resuspended road dust (300 and ...

Toxicity of chemical components of ambient fine particulate matter (PM 2.5) inhaled by aged rats

The toxicity of two important chemical components of fine ambient particulate matter (PM 2.5)—ammonium bisulfate (ABS) and elemental carbon (C)—was studied using aged (senescent) rats. The study tested the hypotheses that fine particle exposure can damage lungs and impair host defenses in aged rats and that ozone would potentiate the toxicity of these particles. Ammonium bisulfate aerosols were generated by nebulization of dilute aqueous solutions. Elemental carbon was generated from an aqueous suspension of carbon black. Carbon and ABS mixtures were generated by nebulization of a suspension of carbon black in a dilute aqueous solution of ABS. Rats were exposed, nose‐only, for 4 h a day, three consecutive days a week, for 4 weeks. The rats were exposed to one of six atmospheres: (1) purified air; (2) C, 50 μg m−3, 0.3 μm mass median aerodynamic diameter (MMAD); (3) ABS, 70 μg m−3, 0.3 μm MMAD; (4) O3, 0.2 ppm; (5) ABS + C, 0.46 μm MMAD; and (6) ABS + C + O3, 0.45 μm MMAD. Data were analyzed using ANOVA and Tukey multiple comparison tests; a two‐tailed significance level of 0.05 was used. The nuclei of lung epithelial and interstitial cells were examined to determine the labeling of the DNA of dividing cells by 5‐bromo‐2‐deoxyuridine and to identify the location of injury‐repair‐related cell replication. Increased labeling of both epithelial and interstitial lung cells occurred following all pollutant exposures. Although epithelial cells are most likely impacted by inhaled particles first, the adjacent interstitial cells were the cells that showed the greatest degree of response. Exposure to the ABS + C + O3 mixture resulted in losses of lung collagen and increases in macrophage respiratory burst and phagocytic activities that were statistically significant. Our results demonstrate that ozone can increase the toxicity of inhaled particles (or vice versa), and suggest that detailed study of mixtures could provide a more comprehensive understanding of the mechanisms by which inhaled pollutants adversely affect human health. Copyright