Biomedical subjects

Christian C Voigt

Publications and source records attributed to Christian C Voigt.

10 recordsLinked to original sources

PubMed2006

Non-invasive blood sampling from primates using laboratory-bred blood-sucking bugs (Dipetalogaster maximus; Reduviidae, Heteroptera).

Primates are easily stressed by the conventional veterinary blood sampling routine and consequently, measured blood parameters may be biased. In this study, we tested blood-sucking bugs (Dipetalogaster maximus) on one lemur and two ape species (Microcebus murinus, Pongo abelii, Pan paniscus) as an alternative, non-invasive technique for bleeding primates. Within time periods of between 6 and 62 min we obtained blood volumes of 0.01-2.4 ml in 11 out of 12 trials from all three species. Therefore, we conclude that these bugs represent a new, gentle and effective tool for bleeding captive primates without stress.

Animals↗

PubMed2006

An alternative, less invasive blood sample collection technique for serologic studies utilizing triatomine bugs (Heteroptera; Insecta).

The collection of blood samples for serological studies is often stressful for the focus animal. Recently, the use of bloodsucking bugs, such as Dipetalogaster maximus or Triatoma infestans (Reduviidae; Triatominae; Heteroptera), has been suggested as a new and less invasive method for blood collection. To evaluate this technique, we collected paired blood samples from 20 domestic rabbits (Oryctolagus cuniculus) during a study of rabbit hemorrhagic disease virus (RHDV). For each rabbit, blood samples were collected by the conventional method (needle and syringe from the vena auricularis) and through feeding by D. maximus. Samples were tested for RHDV antibodies using standard test kits at three different dilutions. Antibody titers were identical for 56 paired samples and differed in only four cases. The simple matching indices were 1 for the 1:10 dilution and 0.9 for the 1:100 and 1:1000 dilutions. The major advantages of the new technique are 1) the possibility to obtain blood from animals where veins are inaccessible and 2) the fact that anesthesia of focus animals may not be necessary.

Animals↗

PubMed2005

Field metabolic rates of phytophagous bats: do pollination strategies of plants make life of nectar-feeders spin faster?

Recently, it was argued that extrinsic factors, such as high foraging costs, lead to elevated field metabolic rates (FMR). We tested this suggestion by comparing the FMR of nectar-feeding and fruit-eating bats. We hypothesized that the foraging effort per energy reward is higher for nectar-feeding mammals than for fruit-eating mammals, since energy rewards at flowering plants are smaller than those at fruiting plants. Using the doubly labelled water method, we measured the FMR of nectar-feeding Glossophaga commissarisi and fruit-eating Carollia brevicauda, which coexisted in the same rainforest habitat and shared the same daytime roosts. Mass-specific FMR of G. commissarisi exceeded that of C. brevicauda by a factor of almost two: 5.3+/-0.6 kJ g(-1) day(-1) for G. commissarisi and 2.8+/-0.4 kJ g(-1) day(-1) for C. brevicauda. Since nectar-feeding bats imbibe nectar droplets of only 193 J energy content during each flower visit, a G. commissarisi bat has to perform several 100 flower visits per night to meet its energy requirement. The fruit-eating C. brevicauda, on the other hand, needs to harvest only 3-12 Piper infructescenses per night, as the energy reward per Piper equals ca. 6-30 kJ. We argue that the flowering and fruiting plants exert different selective forces on the foraging behaviour and energetics of pollinators and the seed dispersers, respectively. A comparison between nectar-feeding and non-nectar-feeding species in various vertebrate taxa demonstrates that pollinators have elevated FMRs.

Animals↗

PubMed2005

Blood-sucking bugs as a gentle method for blood-collection in water budget studies using doubly labelled water.

During doubly-labelled water (DLW) experiments, blood collection by venous puncture may traumatize animals and consequently affect the animals' behaviour and energy budget. Recent studies have shown that blood-sucking bugs (Triatominae; Heteroptera) can be used instead of conventional needles to obtain blood from animals. In this paper, we validate the bug method in captive nectar-feeding bats, Glossophaga soricina, for water budget analysis by comparing the daily water flux estimated with the DLW method with values measured by an energy balance method. As the mean daily water flux of the DLW method was not significantly deviating from the expected value, blood-sucking bugs may substitute more invasive methods of blood collection in DLW experiments. Based on the DLW estimates, daily energy and water intake rates were calculated and compared to values measured with the energy balance method. The DLW method and the energy balance method yielded on average similar results regarding the daily energy intake (DLW method: 48.8+/-14.2 kJ d(-1) versus energy balance method: 48.1+/-9.9 kJ d(-1)) and daily water intake (DLW method: 13.7+/-2.4 mL d(-1) versus energy balance method: 14.7+/-3.0 mL d(-1)). Based on the calculated water and sugar intake per day, we estimated the sugar concentration of ingested nectar to equal on average 16.2+/-2.4% (mass/mass), which fell close to the measured sugar concentration of 17% (mass/mass) bats fed on during the experiment. We conclude that it is possible to extrapolate mean daily energy and water intake for animal groups, populations and species based on DLW estimates, but due to the large variance of results (low accuracy), it seems inadequate to calculate values for single individuals.

Animals↗

PubMed2005

The energetics of trading nuptial gifts for copulations in katydids.

During copulation, male Isophya kraussi transfer a large nuptial gift to females. In this study, we hypothesized that the energy content of spermatophores should meet the energy requirements of both body maintenance and egg production of females. We measured the field metabolic rate of male and female I. kraussi using the doubly labeled water method and the energy content of spermatophores and male bodies with microbomb calorimetry. The energy content of male nuptial gifts averaged 0.66+/-0.09 kJ, approximately 20% of the total body energy content of male I. kraussi (3.24+/-0.26 kJ). Field metabolic rates averaged 0.41+/-0.17 kJ d(-1) (n = 8) for males and 0.30+/-0.15 kJ d(-1) (n = 5) for female I. kraussi. Thus, the energy content of spermatophores exceeded the daily energy requirements of existence in male I. kraussi. A single nuptial gift provides for all energy requirements of females for 1 or 2 d, depending on their activity, egg production, and ambient temperature. Because the shortest known remating interval of female katydids varies between 1 and 3 d, female I. kraussi could theoretically exist exclusively on spermatophores to meet their nutritional requirements.

Animals↗

PubMed2004

The power requirements (Glossophaginae: Phyllostomidae) in nectar-feeding bats for clinging to flowers.

Nectar-feeding bats are the heaviest pollinators exploiting flowers in a hovering foraging mode. As hovering flight is considered to be energetically costly, clinging to flowers would be beneficial from an energetic perspective. I examined the rate of oxygen consumption and carbon dioxide release during clinging flower visitation in two 10-g Glossophaga soricina (Glossophinae: Phyllostomidae) to evaluate the potential energetic benefit of clinging versus hovering. In addition, I measured the duration of flower visits of free-ranging glossophagine bats to Markea neurantha (Solanaceae), a bat-pollinated plant that allows both hovering and clinging flower visitation. After 20 s of clinging to an artificial respiratory mask, the bats' respiratory exchange ratio did not significantly deviate from 1, indicating the combustion of sugar. The average oxygen uptake rate equaled 1.39 ml min(-1) (+/-0.38 SD, STPD) and the carbon dioxide release rate equaled 1.33 ml min(-1) (+/-0.20 SD, STPD) for feeder visits longer than 20 s (n = 79). Converting the oxygen uptake rate into power input yielded 0.49 W, less than a third of the power requirements for hovering for a 10-g bat. Free-ranging 10-g glossophagine bats exploited flowers of M. neurantha for, on average, 0.32 s (+/-0.14 SD, n = 273) during hovering and for 0.39 s (+/-0.18 SD, n = 152) during clinging visitations. A comparison between the power requirements of flower exploitation in differently sized bats indicates that clinging would benefit larger nectar-feeding bats to a greater extent than smaller species.

Animals↗

PubMed2004

Validation of a minimally invasive blood-sampling technique for the analysis of hormones in domestic rabbits, Oryctolagus cuniculus (Lagomorpha).

Previous studies in small mammals showed that blood-sucking bugs (Reduviidae, Heteroptera) can be used to obtain blood from veins difficult to access by human experimenters. In the present study, we validated the use of reduviid bugs for endocrinological studies in endotherms using domestic rabbits as a model organism. Two processes could alter the hormone concentrations in the blood ingested by the bug: (1) Mixing of ingested blood with saliva, gut fluid, or hemolymph and (2) digestive processes. We compared concentrations of progesterone, testosterone, and hydrocortisone in blood samples that were acquired from domestic rabbits (Oryctolagus cuniculus) by bugs (Dipetalogaster maxima) with hormone concentrations in blood obtained from the same individual rabbits with a conventional method, i.e., syringe. We found no significant differences in hormone concentrations between the two methods. Thus, the mixing effect is negligible immediately after the blood meal. In addition, we also could not find significant changes in concentrations of progesterone and hydrocortisone for up to 8h after the blood meal. Whereas levels of hydrocortisone remained unchanged for even 24h, progesterone levels significantly increased between eight and 24h. Thus, the bugs' excretory apparatus did not fractionate between water and hormones. Thirdly, we hypothesized that reduviid bugs impose less stress on the rabbits than the conventional method. We showed that deviations in hydrocortisone concentrations between the two blood sampling routines were lower when the bug method was used first and higher when the conventional method was used first. Thus, bugs imposed less stress on the study animals than the conventional method. Overall, we conclude that reduviid bugs present a minimally invasive method for obtaining blood from endotherm animals for endocrinological studies.

Animals↗

PubMed2004

Nitrogen stress causes unpredictable enrichments of 15N in two nectar-feeding bat species.

We estimated the effect of nitrogen stress on the nitrogen isotope enrichments in wing membrane and blood of two nectar-feeding bats (Glossophaga soricina and Leptonycteris curasoae) by offering a nitrogen-poor diet with a high delta(15)N and delta(13)C. Before the experiment, bats were sustained on a normal diet with a low delta(15)N and delta(13)C. Under this first food regime, the fractionation of nitrogen isotopes averaged 3.1 per thousand delta(15)N for blood and 4.4 per thousand delta(15)N for wing membrane, which was almost twice as high as the corresponding fractionation of carbon isotopes. After switching to the nitrogen-poor diet, the enrichment of heavy isotopes increased for both elements in all tissues under study. The recently published estimates of half-life of carbon isotopes indicated a low turnover rate of carbon in wing membrane and blood and an almost constant half-life over varying losses of body mass. The estimates of half-life of nitrogen were two to six times higher than those of carbon. We argue that this discrepancy was caused by the mixing of nitrogen isotopes from internal and external sources. The mixing effect was probably negligible for carbon as the amount of ingested carbon outweighed the amount of mobilized carbon from internal sources. A correlation between the estimated turnover rates of nitrogen and losses of body masses was probably obscured by the additional fractionation of nitrogen isotopes in catabolic animals. We conclude that the interpretation of nitrogen isotope data of free-ranging animals is difficult when the animal's diet is changing to a critical nitrogen content.

Analysis of Variance↗

PubMed2003

Validation of a non-invasive blood-sampling technique for doubly-labelled water experiments.

Two techniques for bleeding small mammals have been used in doubly-labeled water (DLW) studies, including vena puncture and the use of starved nymphal stages of hematophagous reduviid bugs (Reduviidae, Hemiptera). In this study, we tested the validity of using reduviid bugs in doubly-labeled water experiments. We found that the isotope enrichment in initial blood samples collected with bugs was significantly lower compared to isotope enrichment in blood samples obtained using vena puncture. We therefore used the desiccation method for estimating total body water (TBW) in DLW experiments because TBW calculated using the isotope dilution method was overestimated when blood samples were collected using reduviid bugs. In our validation experiment with nectar-feeding bats (Glossophaga soricina), we compared estimates of daily energy expenditure (DEE) using DLW with those derived from the energy balance method. We considered Speakman's equation (controlling for 25% fractionated water loss) as the most appropriate for our study animal and calculated DEE accordingly. On average, DEE estimated with DLW was not significantly different from the mean value obtained with the energy balance method (mean deviation 1.2%). We conclude that although bug hemolymph or intestinal liquids most likely contaminate the samples, estimates of DEE are still valid because the DLW method does not depend on absolute isotope enrichments but on the rate of isotope decrease over time. However, dilution of blood with intestinal liquids or hemolymph from a bug may lead to larger variation in DEE estimates. We also tested how the relative error of DLW estimates changed with varying assumptions about fractionation. We used three additional equations for calculating DEE in DLW experiments. The basic equation for DLW experiments published by Lifson and McClintock (LM-6) assumes no fractionation, resulted in an overestimate of DEE by 10%. Nagy's equation (N-2) controls for changes in body mass but not for fractionation. Using Nagy's equation, DEE was overestimated by 8%. Under the assumption that 50% of total water flux fractionates, the alternative equation by Lifson and McClintock (LM-35) DEE was underestimated by 5%. The best fit between estimates of DEE based on DLW and energy balance measurements was derived by assuming that 32% of total water flux (TWF) is fractionated. We conclude that the outcome of DLW experiments is sensitive to assumptions regarding evaporative water loss, and thus recommend Speakman's equation 7.17 for use with bats.

Animals↗

PubMed2003

Low turnover rates of carbon isotopes in tissues of two nectar-feeding bat species.

Stable isotopes of carbon are commonly used to characterize dietary preferences in animals. Because turnover rates of carbon isotopes are related to metabolic rate, we wanted to determine the rates at which carbon isotopes are exchanged in tissues of two species of nectar-feeding bats (Leptonycteris curasoae and Glossophaga soricina), both of which have relatively high mass-specific metabolic rates. To test the hypothesis that isotope turnover is higher in nectar-feeding bats, because of their high mass-specific metabolic rates, than in other eutherian mammals, we conducted diet-switching experiments and chose three target tissues (hair, wing membrane and blood) to evaluate the isotopic turnover rates. We made the following predictions: (1) isotopic composition should change towards higher delta(13)C-values due to the turnover of carbon isotopes of C(3) origin with those of C(4)/CAM origin; (2) the turnover rates of carbon isotopes would differ between the three types of tissues in the following order of decreasing turnover rates: blood>wing membrane>hair; and (3) turnover rates of nectar-feeding bats should exceed those reported for other small mammals because of the high mass-specific metabolic rate of nectar-feeding bats. Compared to the initial diet, target tissues were enriched in heavy carbon isotopes by 2.8 per thousand in L. curasoae and by 2.6 per thousand in G. soricina. After changing the diet from C(3) to C(4)/CAM origin we found an increase in abundance of (13)C in blood and wing membrane in all experimental subjects. The estimated half life of carbon isotope turnover ranged from 100 to 134 days and did not differ significantly between blood and wing membrane, nor did it differ between the two species. The low turnover rate in wing membrane may reflect its specific composition and the relatively low temperature of this tissue, and long-lived erythrocytes in bat blood may be responsible for the low turnover rate of carbon isotopes in blood. The turnover rate of stable carbon isotopes in hair was low in L. curasoae and undetectable in G. soricina, which may be explained by the seasonal growth of the hair in these two species. Because both species are small (10 and 25 g, respectively) and nectar-feeding bats have higher mass-specific metabolic rates than bats in temperate regions or similar sized terrestrial mammals, our findings of low turnover rates were unexpected.

Analysis of Variance↗