Compensatory investment in zebra finches: females lay larger eggs when paired to sexually unattractive males

The classical version of the differential allocation hypothesis states that, when females reproduce over their lifetime with partners that differ in their genetic quality, they should invest more in reproduction with high-quality males. However, in species with lifetime monogamy, such as the zebra finch, partner quality will typically remain the same. In this case, the compensatory investment (CI) hypothesis predicts higher investment for low-quality males, because low genetic quality offspring are more dependent on maternal resources. Here, we show that female zebra finches invested more resources, both in terms of egg volume and yolk carotenoid content, when paired to a low genetic quality male, as judged from his previous ability to obtain extra-pair paternity in aviary colonies. We also found that females deposited slightly larger amounts of testosterone into eggs when paired to a low parental quality male, as judging from his previous success in rearing offspring. This is, to our knowledge, the first experimental support for the CI hypothesis in a species with lifetime monogamy. We stress that in more promiscuous species, the benefits of classical differential allocation may partly be neutralized by the supposed benefits of CI.     

Great tits, Parus major, lay too many eggs: experimental evidence in mid-boreal habitats

This study shows that great tits lay too large clutches in mid‐boreal habitats. First, breeding success, measured with number of fledglings or proportion of eggs that produce fledglings, in northern Finland (65°N) is much poorer than in central and western Europe. Second, brood size manipulations (ca ±30% of the natural mean) revealed that reduced broods produced equal numbers of and larger‐sized fledglings than control and enlarged broods, giving thus the best fitness value for reduced broods. Third, parents of enlarged broods could not adjust (i.e. increase) their feeding effort to the greater number of nestlings. Fourth, extra feeding (about 1/3 of the theoretical maximal needs of the nestlings) during the nestling period resulted in more numerous and larger‐sized fledglings in comparison to control broods. We suggest that the ultimate explanation for the too large clutches is gene flow from the southern population, which prevents local adaptations in the north. Consequently, the main reason for food limitation during the nestling period is that northern great tits apply “southern” decision rules for timing of breeding, clutch size and foraging behaviour. Thus, they tend to breed too early in comparison to the food abundance peak, lay too large clutches in comparison to the level of resources and, perhaps, forage on a too narrow diet (75% caterpillars). Since the late broods that matched the local food abundance peak did not succeed better than the mismatched earlier ones, the most crucial fault of northern great tits seems to be that they overestimate food abundance during peak demands and lay too large clutches. Another explanation for this could be that northern great tits have adopted a brood reduction strategy. However, the long‐term data reveal that years of high breeding success, which would maintain large clutches in the population, are very rare in the north. Therefore, it is unlikely that a brood reduction strategy per se could explain the phenomenon. Instead, it could work together with the gene flow against local adaptation for clutch adjustment.     

Reproductive allocation in Aidablennius sphynx (Teleostei, Blenniidae): females lay more eggs faster when paired with larger males

Individuals are expected to invest more in current reproductive effort when paired with a partner of higher than average quality. Aidablennius sphynx is an external fertilizing fish with paternal care in which females gain direct benefits from spawning with large males, but often 'make do' with small males. In this study, female reproductive responses to large and small males were investigated. When paired with large males, females spawned more eggs per unit time (i.e., at a faster rate). There was no difference in the size of the eggs spawned by females in relation to partner size. By ovipositing at a faster rate, females may have allocated more reproductive effort to large males. In addition, since small males are known to release far fewer sperm than large males, females may have reduced their spawn rate with small males as a tactic to ensure fertilization.     

Differential allocation in a lekking bird: females lay larger eggs and are more likely to have male chicks when they mate with less related males

The differential allocation hypothesis predicts increased investment in offspring when females mate with high-quality males. Few studies have tested whether investment varies with mate relatedness, despite evidence that non-additive gene action influences mate and offspring genetic quality. We tested whether female lekking lance-tailed manakins (Chiroxiphia lanceolata) adjust offspring sex and egg volume in response to mate attractiveness (annual reproductive success, ARS), heterozygosity and relatedness. Across 968 offspring, the probability of being male decreased with increasing parental relatedness but not father ARS or heterozygosity. This correlation tended to diminish with increasing lay-date. Across 162 offspring, egg volume correlated negatively with parental relatedness and varied with lay-date, but was unrelated to father ARS or heterozygosity. Offspring sex and egg size were unrelated to maternal age. Comparisons of maternal half-siblings in broods with no mortality produced similar results, indicating differential allocation rather than covariation between female quality and relatedness or sex-specific inbreeding depression in survival. As males suffer greater inbreeding depression, overproducing females after mating with related males may reduce fitness costs of inbreeding in a system with no inbreeding avoidance, while biasing the sex of outbred offspring towards males may maximize fitness via increased mating success of outbred sons.     

Measurement of ad libitum food intake, physical activity, and sedentary time in response to overfeeding

Given the wide availability of highly palatable foods, overeating is common. Energy intake and metabolic responses to overfeeding may provide insights into weight gain prevention. We hypothesized a down-regulation in subsequent food intake and sedentary time, and up-regulation in non-exercise activity and core temperature in response to overfeeding in order to maintain body weight constant. In a monitored inpatient clinical research unit using a cross over study design, we investigated ad libitum energy intake (EI, using automated vending machines), core body temperature, and physical activity (using accelerometry) following a short term (3-day) weight maintaining (WM) vs overfeeding (OF) diet in healthy volunteers (n?=?21, BMI, mean ± SD, 33.2±8.6 kg/m(2), 73.6% male). During the ad libitum periods following the WM vs. OF diets, there was no significant difference in mean 3-d EI (4061±1084 vs. 3926±1284 kcal/day, p?=?0.41), and there were also no differences either in core body temperature (37.0±0.2°C vs. 37.1±0.2°C, p?=?0.75) or sedentary time (70.9±12.9 vs. 72.0±7.4%, p?=?0.88). However, during OF (but not WM), sedentary time was positively associated with weight gain (r?=?0.49, p?=?0.05, adjusted for age, sex, and initial weight). In conclusion, short term overfeeding did not result in a decrease in subsequent ad libitum food intake or overall change in sedentary time although in secondary analysis sedentary time was associated with weight gain during OF. Beyond possible changes in sedentary time, there is minimal attempt to restore energy balance during or following short term overfeeding. Trial registration: ClinicalTrials.gov NCT00342732.     

Female canaries produce eggs with greater amounts of testosterone when exposed to preferred male song

Male birdsong has a great influence in the stimulation of female reproduction. However, female physiological responsiveness to song may depend on the degree of complexity of male song. This is expected because females of iteroparous organisms may increase their fitness by matching their reproductive investment to the predicted value of each reproductive attempt. To the extent that the expression of male ornaments is a signal of male quality, we expect females to increase their investment when paired to highly ornamented males. However, female investment may be cryptic and difficult to detect, such as androgen content in the eggs. In this study, we exposed female canaries (Serinus canaria) to attractive and unattractive song repertoires using a crossover design. As predicted, females invested greater concentrations of testosterone in their eggs when exposed to attractive repertoires than when exposed to unattractive repertoires. This implies that song repertoires convey important information about the reproductive value of a given male and suggests that testosterone deposition in egg yolk may be costly.     

The effect of acclimation upon the survival of Ptinus tectus and Tenebrio molitor when exposed to low temperatures

Ptinus tectus and Tenebrio molitor adults were acclimated for 24 hours to 15°, 25° and 35°. Evidence of acclimation was given by measurement of the chill coma point, heart beat and respiration rates. The respective chill coma points for insects acclimated to 15°, 25° and 35° were 2.9°, 3.7° and 4.7° for P. tectus, and 5.4°, 6.9° and 8.3° for T. molitor. The rates of heart beat and oxygen intake showed that P. tectus could acclimate from 25° to 15° but not to 35°, whilst T. molitor could acclimate from 25° to 35° but not to 15°. Acclimation also affected the undercooling point and fat content, but not the water content. The acclimated insects were exposed to a range of low temperatures for varying periods of time and allowed to recover at 15°, 25° or 35°. The dosage mortality data produced were subjected to probit analyses. In both species mortality varied with the time and temperature of exposure. In P. tectus there was a zone of resistance to freezing extending from 0° (L.D.₅₀=1820h) to -9° (L.D.₅₀=49–76h) and acclimation affected the terminal region (-9° to-12°) of this zone by altering the undercooling point. Resistance to freezing was minimal in T. molitor and was unaffected by acclimation. The time taken to recover in both species varied with the recovery temperature and the quantity and intensity of cold, but was unaffected by acclimation.

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Résumé Ptinus tectus et Tenebrio molitor furent maintenus pendant 24 h à des températures de 15°, 25° et 35°, puis testés quant à leur résistance au froid, par la détermination de la température provoquant le coma et par les variations de leur rythme cardiaque ou de leur consommation d'oxygène. Dans les deux espèces on observe que le coma se manifeste pour une température d'autant moins basse que la température d'acclimatation était plus élevée. Les adultes de ces mêmes insectes ont été exposés à des températures sub-létales inférieures à 0°, pendant des durées variables, puis ramenés à des températures de 15°, 25° et 35°. La mortalité est alors estimée et comparée entre des lots préalablement acclimatés à tem températures de 15°, 25° et 35°. Chez les deux espèces étudiées la mortalité augmente avec la durée d'action de la température sub-létale (facteur quantité) et avec la baisse de température subie (facteur intensité). La température d'acclimatatio ppréalable n'affecte pas, chez Tenebrio molitor la D.L. 50, alors que chez Ptinus tectus il se révèle qu'une acclimatation à la plus basse température, diminue la mortalité après action de températures sub-létales comprises entre-9° et-12°. On a également comparé le taux de mortalité pour des températures égales ou supérieures à 0° (6°-15°-25°-29°-35°) chez des insectes acclimatés à 25° et ramenés à cette température après action du froid. La mortalité minimun s'observe alors pour une température de restauration de 15°. Les températures de surfusion, la teneur en eau et en lipides furent précisées pour chacun de ces insectes, en rapport avec la température d'acclimatation à laquelle ils avaient été préalablement soumis.

     

Human neutrophils permeabilized with digitonin respond with lysosomal enzyme release when exposed to micromolar levels of free calcium

We have recently reported that human neutrophils can be permeabilized with the cholesterol complexing agent saponin and that these cells can be induced to secrete the granule enzyme lysozyme in response to micromolar levels of free calcium. We now report that digitonin can be used in place of saponin and that it has several advantages. Permeabilization of human neutrophils was accomplished with 10 micrograms/ml digitonin in a high potassium medium. Normally impermeant solutes such as [14C]sucrose and inulin [14C]carboxylic acid gained access to one half of the intracellular water space marked with [3H]H2O. Between 30 and 100% of the cytoplasmic enzyme, lactate dehydrogenase, leaked from the intracellular space. The permeabilization process and calcium-triggered granule secretion were critically dependent upon temperature, time and digitonin concentration. Permeabilized neutrophils secreted beta-glucuronidase, lysozyme and vitamin B-12 binding-protein, constituents of both azurophil and specific granules, when exposed to micromolar levels of free calcium. Release of specific granule constituents appeared to be more sensitive to free calcium than release from azurophil granules. Although the amount of permeabilization varied considerably with each batch of cells, release of these granule markers was a consistent finding. Release of granule markers was accompanied by resealing of the cells to high-molecular-weight (Mr greater than 5000) solutes. Electron microscopic evidence also suggested that granule and plasma membranes were intact following digitonin treatment and that fusion of these membranes occurred in response to calcium. These results suggest that elevation of intracellular free-calcium levels is a sufficient condition for lysosomal enzyme release.     

Effect of roughage level in a total mixed ration on feed intake, ruminal fermentation patterns and chewing activity of early-weaned calves with ad libitum access to grass hay

In this study, two total mixed rations (TMR, based on dry ingredients) consisting (per kg dry matter (DM)) of 300 or 400 g finely chopped hay mixture of grass and alfalfa (H30 versus H40) were compared concerning their effects on dry matter intake (DMI), ruminal fermentation patterns and chewing activity of early-weaned (8 weeks milk-fed) calves. Ten ruminally cannulated male German Holstein calves were randomly assigned to two dietary treatments (n = 5) and observed from an age of 8–15 weeks. One group received the H30 (11.3 MJ metabolizable energy (ME)/kg DM) and the other the H40 (10.7 MJ ME/kg DM) TMR. All calves received grass hay (9.0 MJ ME/kg DM) separately. Water, TMR and hay were offered ad libitum twice daily (08:00 and 16:00 h). Rumen fluid was collected via cannula at an age of 9, 11, 13 and 15 weeks, twice weekly just prior to as well as 1, 3, 5 and 7 h after morning feeding. Chewing activity was recorded by a special head collar. As the calves aged DMI increased rapidly congruent with the recommended range for weaned calves. Because of the differing energy supply, calves receiving the H30 TMR were heavier than calves receiving the H40 TMR (139 kg versus 123 kg, P=0.007). During the trial ruminal pH of all calves were within the target range (6.2 ± 0.5), indicating physiological ruminal fermentation patterns. Daily mean ruminal pH was uninfluenced by treatment, however at an age of 13 and 15 weeks H30 showed a higher short chain fatty acid (SCFA) level than H40 (P=0.098; P=0.036). At an age of 15 weeks H30 showed a critical decrease in ruminal pH (3 h after feeding: 5.7) corresponding to a higher ruminal SCFA concentration (148.2 mmol/L, P=0.007). Chewing activity was well developed at an early age due to an increasing DMI after weaning. At an age of 15 weeks chewing activity (per day: 613–743 min total chewing; 358–418 min rumination) was similar to that of adult cows. In summary, feeding a dry TMR consisting per kg DM of 300–400 g hay to early-weaned calves can be recommended for a successful calf rearing up to an age of 15 weeks.     

Stability of a single-chain Fv antibody fragment when exposed to a high shear environment combined with air-liquid interfaces

The effect of shear on the antigen binding activity of a recombinant scFv antibody fragment was investigated in the presence of air-liquid interfaces using a stirred vessel that was incompletely filled. Changes in binding activity of the scFv to its antigen were monitored using an optical biosensor which had been sensitized with hen egg lysozyme (the antigen). The biosensor response was used as a measure of scFv binding activity. In buffer solution (mean velocity gradient approximately 20,000 s-1), loss of binding activity followed a first-order model with a mean rate constant of 0.83 h-1. In unstirred buffer solution, no such loss was observed. Similarly, in sheared fermentation broth there was no loss of binding activity and protective effects were attributed to the antifoam PPG.     

Histopathological changes in livers of mice infected with tetrathyridia of Mesocestoides corti and exposed to different environmental temperatures

Novak M. 1982. Histopathological changes in livers of mice infected with tetrathyridia of Mesocestoides corti and exposed to different environmental temperatures. International Journal for Parasitology12: 41–45. Observations on the histopathology of the liver of mice infected with Mesocestoides corti and kept for 20 days p.i. (post-infection) at low (5 ± 1°C), room (21 ± 1°C) or high (35 ± 1°C) temperature revealed that the degree of liver pathology was directly proportional to the intensity of liver infection, which in turn was the result of the temperature effect. The most severe pathological changes occured in the heavily infected organs of mice kept at low temperature, followed by less prominent changes in moderately infected livers of mice kept at room temperature and the smallest changes in lightly infected livers of mice kept at high temperature. The pathological changes in infected and uninfected livers of hosts exposed to different environmental temperatures are described and compared.     

Aluminium resistance requires resistance to acid stress: a case study with spinach that exudes oxalate rapidly when exposed to Al stress

Spinach is a vegetable with a high oxalate concentration in its tissues. Oxalate efflux from spinach (Spinacia oleracea L. cv. Quanneng) roots was rapidly stimulated (within 30 min) by aluminium (Al) treatment. The efflux was constant within 6 h, but increased with increasing Al concentration. The efflux was confined to the root tip (0-5 mm), which showed a 5-fold greater efflux than the root zone distal to the tip (5-10 mm). Oxalate efflux could not be triggered by treatment with the trivalent cation lanthanum or by phosphorus deficiency, indicating that the efflux was specific to the Al treatment. All this evidence suggested that spinach possesses Al-resistance mechanisms. However, spinach was found to be as sensitive to Al toxicity as the Al-sensitive wheat line ES8, which had no Al-dependent organic acids efflux. The Al accumulated in the apical 5 mm of the roots of spinach which was also similar to that in the Al-sensitive wheat after 24 h treatment with 50 microM AlCl(3), indicating a non-exclusion mechanism. In addition, root elongation in spinach was significantly inhibited at pH 4.5, compared with that at pH 6.5. Based on this evidence, it is concluded that the sensitivity to acid stress in spinach could mask the potential role for oxalate to protect the plant roots from Al toxicity.     

Great adaptability of brown adipose tissue mitochondria to extreme ambient temperatures in control and cold-acclimated gerbils as compared with mice

1. The gerbil (Gerbillus campestris) is a desert rodent able to tolerate high (38 degrees C) and low (-20 degrees C) ambient temperatures, probably due to both its low resting metabolic rate in hot environment and its high peak metabolic rate in cold. 2. Measurement of mitochondrial state IV respiration and cytochrome-oxidase activity (COX) were made in interscapular brown adipose tissue (IBAT), liver and hind limb muscles of gerbils and mice of nearly equal body mass, acclimated for 4 weeks at cold ambient temperature (CA) or reared at thermoneutrality (TN). 3. The most striking difference between these two animal species appears to be in IBAT mitochondria: in TN animals, the level of state IV respiration and COX activity was lower in gerbils than in mice, but the cold acclimation-induced increase in these parameters was greater in gerbils than in mice. 4. Alternatively, in gerbils as in mice, cold acclimation induced a reduction in muscle mitochondrial COX activity. No important change due to cold acclimation was observed in liver mitochondria, either in gerbils or in mice. 5. As compared with mice, the lower state IV respiration in IBAT mitochondria from TN gerbils may explain their low RMR, whereas the higher COX activity of IBAT mitochondria from CA gerbils may explain their higher PMR. 6. As a result of this great adaptability of BAT mitochondria, the gerbil seemed to be able to live in a wide range of ambient temperatures in its natural habitat.     

Microtubules at wound sites of Nitella internodal cells passively co-align with actin bundles when exposed to hydrodynamic forces generated by cytoplasmic streaming

The organization of cortical microtubules at wound sites in Nitella pseudoflabellata(A. Br. & Nordst.) em. R.D.W. and N. flexilis(L.) Ag. internodal cells was examined in relation to the regeneration of actin filament bundles in order to identify the mechanisms by which microtubules are oriented. Actin bundle regrowth occurs prior to that of microtubules, so it was considered possible that microtubule alignment is actin-dependent, perhaps mediated by cross-linking proteins. In all types of wounds investigated, subcortical actin bundles regenerated parallel to the direction of cytoplasmic streaming. Microtubule orientation patterns, however, varied according to the nature of wound formation and the type of wound wall eventually produced. In chloroplast-free windows induced by blue light irradiation, microtubule orientation varied according to the size of the window. Microtubules were randomized in 10- to 30-μm-wide windows where exposure to cytoplasmic flow is minimal, but were aligned more or less parallel to regenerated actin bundles in 80- to 100-μm-wide windows. Where co-alignment between microtubules and actin bundles was obvious after fluorescence labelling, electron micrographs revealed that microtubules and actin bundles were too widely spaced to account for any cross-linkages. Furthermore, treatments that inhibited or reduced cytoplasmic streaming without altering the direction of actin bundles caused randomization of microtubules previously oriented in the streaming direction, even in the presence of taxol. When evenly flat wound walls were induced by 10⁻⁴ M chlortetracycline, microtubules were co-aligned with nearby actin bundles at the surface of the wound wall. At wounds induced by treatment with 5 × 10⁻² M CaCl₂, however, microtubules were randomly oriented and preferentially located in the narrow clefts between the wound-wall protuberances, up to several micrometers away from the actin bundles near the wound-wall tips. These results indicate that microtubules regenerated in wounds are merely co-aligned with actin filament bundles because they are passively aligned by the hydrodynamic forces created by cytoplasmic flow. Received: 4 August 1998 / Accepted: 30 January 1999     

Susceptibility to damage of human lymphocyte chromosomes in different stages of the mitotic cycle when exposed to fast neutrons with an average energy of 6 MeV

Cytogenetic susceptibility of human lymphocytes in the culture to lesion is studied under the effect of neutrons with 6 MeV energy at different stages of the mitotic cycle. Radiosensitivity of human lymphocytes under the influence of gamma-quanta and neutrons is found to vary identically during the whole cycle. These variations are less expressed in the case of neutron irradiation. The data allow concluding that the repair system functions most actively at the S stage in case of both types of radiation.