Incubation energetics of the Laysan Albatross

Summary The energy expenditure of incubating and foraging Laysan Albatross (Diomedea immutabilis, mean body weight 3.07 kg) was estimated by means of the doubly-labelled water technique. During incubation, the energy expenditure was similar to that of resting birds that were not incubating an egg. The energy expenditure of foraging albatross (2072 kJ/day) was 2.6 times that of resting birds. It was concluded that the energy expenditure of the tropical Laysan Albatross was not less than that of species foraging over cold, high-latitude oceans. An energy budget compiled for an incubating pair of albatross revealed that the energy expenditure of the female was greater than that of the male bird, during the incubation period.     

Plasmodium berghei: infective exoerythrocytic schizonts in primary monolayer cultures of rat liver cells.

Suspensions of rat liver cells which included hepatic exoerythrocytic schizonts (HEX) of Plasmodium berghei were used to initiate primary monolayer cultures of rat hepatic cells. These cell suspensions were prepared by using an enzymatic method for the dissociation of the livers of rats that had been infected with sporozoites of P. berghei 3 to 10, 18 to 28, and 29 to 36 hr prior to the liver dissociation procedure. These cell suspensions included HEX which were infective for recipient rodents when inoculated intraperitoneally into the recipients. HEX were considered to have been successfully maintained if they retained their infectivity for rodents following the cultivation period. The relative number of infective HEX present in the liver cell suspensions before and after cultivation was determined by use of an infectivity assay. Using this infectivity assay, it was observed that less infective HEX were present in the cell population following cultivation than were present before cultivation. Infective HEX were recovered from culture in experiments in which the time in vitro ranged from 3 to 44 hr. Twelve of fifteen (80%) attempts to maintain infective HEX in culture for 21 to 28 hr were successful, while one of eight (12.5%) attempts to maintain HEX in culture for 36 to 48 hr were successful. Thus, these experiments have provided an 80% success rate for maintaining HEX for a period equivalent to over 50% of the incubation period of HEX of this parasite. This technique should be sufficient for studying in vitro the factors which influence the development of HEX, as well as for testing methods of causal prophylaxis.     

Plasmodium berghei: preparation of rat hepatic cell suspensions that include infective exoerythrocytic schizonts.

Employing an enzymatic method to dissociate rat liver, we prepared suspensions of liver cells from rats infected with sporozoites of Plasmodium berghei 3 to 10, 18 to 28, or 29 to 36 hr prior to liver dissociation. These suspensions of liver cells included hepatocytes, Kupffer cells, fibroblasts, and unidentified cells, as well as hepatocytes infected with exoerythrocytic schizonts (HEX) of P. berghei. These HEX were infective for recipient rodents when inoculated intraperitoneally into the recipients. The number of infective HEX present in the liver cell suspensions was quantitated by varying the number of HEX inoculated into recipients. This infectivity assay made it possible to compare the numbers of HEX in suspensions of liver cells from different donor rats. Infective HEX were obtained from donor rats in 35 of 41 experiments. The greatest number of infective HEX was obtained from donors injected with sporozoites 18 to 28 hr prior to liver dissociation. For morphological observation of mature HEX in cell suspensions, hepatic cells were prepared from donors infected with sporozoites 48 hr prior to liver dissociation. For experimental purposes, the preparation of infective HEX in suspensions of liver cells is superior to the preparation of infective HEX in liver fragments, because it is possible to quantitate the number of HEX which are present either visually or by means of the infectivity assay.     

Effect of elevated carbon dioxide on chicken eggs during the early and late incubation periods

Carbon dioxide (CO₂) is always maintained at ambient levels by ventilation in commercial egg incubators. However, elevated CO₂ levels during the early and late periods have been reported to improve the quality of chicks and shorten the hatch window. This study investigated the effect of precise CO₂ supplementation during the early and late periods of incubation on embryo growth and incubation performance by developing and using a CO₂ supplementation system to increase the CO₂ level in an experimental egg incubator. The CO₂ level was maintained at 1% in the early period (from the beginning to the 10th day of incubation, E0–E10) and in the late period (from internal pipping (IP) to the 21st day of incubation (E21), IP–E21) in an incubator for the treatment group, whereas the CO₂ level was maintained at the ambient level in the other incubators for the control group. A comparative assessment of embryonic development, hatching characteristics, and hormone and nutrient levels was conducted for each trial. The experiment comprised three trials, with 300 Jing Hong No. 1 breeding eggs in each incubator. The elevated CO₂ treatment significantly shortened the chick hatching time (H0) by 4 h (P < 0.05) and the hatch window by 3 h (P < 0.05) without affecting hatchability, chick weight at 1 d of age, brooding period, or quality score. At external pipping (EP), the heart weight, intestinal weight, relative intestinal weight, and relative heart weight in the treatment group were significantly higher than those in the control group (P < 0.05). In addition, the embryonic intestine, relative intestine, and relative heart weights of the newly hatched chicks in the treatment group were significantly higher than those in the control group (P < 0.05) at H0. The treatment significantly increased the concentration of corticosterone in the embryonic plasma during the period from IP to EP (P < 0.05), promoted the secretion of triiodothyronine and tetraiodothyronine (P < 0.05), and increased the glycogen content of the embryonic liver on E21 (P < 0.05). This result indicates that elevated CO₂ (1%) during the early and late periods of incubation accelerated embryonic organ development and shortened the chick hatching time and hatch window without affecting hatchability or hatchling quality, which can be explained by the synergistic functions of the secretion of plasma corticosterone and thyroid hormones and the accumulation of liver glycogen between the early and late periods of incubation.     

菲牛蛭交配及卵茧人工孵化初步研究

人工饲养条件下,比较观察了不同养殖模式(水体、土壤)和不同温度(24℃、26℃、28℃、30℃、32℃和34℃)对菲牛蛭(Hirudinaria manillensis)交配率的影响,并进行了不同卵茧质量(＜0.6 g、0.6～1.0 g、1.0～1.5g、1.5～2.0 g、＞2.0 g)及不同温度(22℃、24℃、...     

Effects of carrier, sterilisation method, and incubation on survival of Bradyrhizobium japonicum in soybean (Glycine max L.) inoculants

The production and quality of rhizobial inoculants in many developing countries is limited by the availability of suitable carriers or technological limitations. Experiments were conducted to evaluate the potential of various inexpensive and widely available carrier materials. The carriers, evaluated, were: perlite with pH adjusted with calcium carbonate or charcoal, 1:4 mixtures of perlite and malt residue, sugarcane bagasse, coal, and rice husk. We also contrasted sterilisation procedures (autoclaving or gamma irradiation) and incubation after injection (with or without initial two weeks incubation at 28 °C) for these various carriers. Survival of Bradyrhizobium japonicum strain CB1809 was monitored over a period of 6 months upon storage at 4 °C. Most carriers evaluated, were able to maintain rhizobial populations of more than 1 × 10⁹ rhizobia per gram of inoculant over that time period, with mixtures of perlite with either sugarcane bagasse or malt residue supporting the largest rhizobial populations and a mixture of perlite and rice husk the lowest. All carriers supported rhizobial growth over the 6 months period. Initially, rhizobial populations were greater with gamma irradiation than autoclaving, however after 6 months, this response was significant only with the perlite and sugarcane bagasse mixture. The incubation of the inoculant after injection also ultimately did not benefit rhizobial levels for any of the carriers, tested. Using simple sterilisation procedures and without incubating after injection, perlite based carriers can produce high quality inexpensive inoculants, maintaining bacterial populations of more than 1 × 10⁹/g rhizobia for at least 6 months.     

Incubation scheduling by Northern Fulmars ( Fulmarus glacialis ) in the Canadian High Arctic

Northern Fulmars (Fulmarus glacialis) are a ubiquitous seabird of the North Atlantic and North Pacific oceans that breed in colonies surrounded by markedly different marine environmental conditions. I have studied the incubation behavior of fulmars at a remote colony in the Canadian High Arctic, where the birds had to cross 200 km of sea-ice during the early incubation period to reach feeding areas. These fulmars completed incubation in fewer shifts and had a longer mean incubation shift duration (5.3 days) than their counterparts breeding in the Boreal oceanographic zone. In particular, the mean duration of the first incubation shift by males in successful pairs (10.3 days) was 2 days longer than that for males in unsuccessful pairs and was longer than that reported at any other colony. This exceptionally long shift by the male may be required at this site to give females enough time to recoup energetic reserves after egg-laying, at a time when marine productivity in the Arctic is still seasonably low.     

Parental sex roles of Malaysian plovers during territory acquisition,incubation and chick-rearing

Shorebirds show high variability in parental care strategies among species, populations, and environments. Research on shorebird parental sex roles can help to understand the selective pressures that shape avian breeding strategies. Although several studies have examined parental care strategies in holarctic shorebirds, very little research has been conducted in the tropics. Here we examined parental sex roles during territorial defence, incubation, and chick-rearing in Malaysian plovers Charadrius peronii in the Gulf of Thailand. The costs and gains of particular parental behaviour may vary between the sexes and can be affected differently by environmental factors and chick age. Thus we also examined how temperature, prey availability, chick or embryo age, and time of day affected parental sex roles. Males spent more time defending territories and were further away from chicks whereas females spent more time incubating eggs. Both adults contributed to chick defence during disturbances throughout the entire chick-rearing period. Total nest attendance (sum of both sexes) was affected by the modelled temperature of an unincubated egg. Prey availability, embryo age, and time of day had no effect on total nest attendance. Males adjusted incubation effort in response to temperature only at high temperatures (>36°C) whereas females adjusted nest attendance at high and low temperatures. Chick age had no effect on the proportion of time adults spent defending territories or responding to disturbance. Pairs were more likely to fledge chicks if both the male and female spent more time defending territories. For Malaysian plovers, high cooperation between the sexes during parental care may help to achieve high quality breeding territories, maintain body conditions during hot days, protect offspring from predators and attacking conspecifics, and contribute to high lifetime reproductive success.     

Avian brood patch temperature: Relationships with female body mass,incubation period,developmental maturity and phylogeny

Brood patch temperatures (BPT) of 76 species of birds were collated from the literature and compared with female body mass (FBM) and incubation period (I_p) of the species concerned.     

Thermal emissivity of avian eggshells

The hypothesis has been tested that evolution has resulted in lower thermal emissivity of eggs of birds breeding openly in cold climates than of eggs of birds that nest under protective covering or in warmer climates. Directional thermal emissivity has been estimated from directional–hemispherical reflectance spectra. Due to several methodological difficulties the absolute emissivity is not accurately determined, but differences between species are obvious. Most notably, small waders of the genus Calidris, breeding in cold climates on the tundra, and in most cases with uniparental nest attendance, have low directional emissivity of their eggshells, about 0.92 when integration is carried out for wavelengths up to 16 μm. Species belonging to Galloanserinae have the highest directional emissivity, about 0.96, of their eggs. No differences due to climate or breeding conditions were found within this group. Eggs of most other birds tested possess intermediate emissivity, but the values for Pica pica and Corvus corone cornix are as low as for Calidris. Large species-dependent differences in spectral reflectance were found at specific wavelengths. For instance, at 4.259 μm the directional–hemispherical reflectance for galliforms range from 0.05 to 0.09, while for Fratercula arctica and Fulmarus glacialis it is about 0.3. The reflection peaks at 6.5 and 11.3 μm due to calcite are differentially attenuated in different species.In conclusion, the hypothesis that evolution has resulted in lower thermal emissivity of bird eggs being exposed in cold climates is not supported by our results. The emissivity is not clearly related to nesting habits or climate, and it is unlikely that the small differences observed are ecologically important. The spectral differences between eggs that nevertheless exist should be taken into account when using infrared thermometers for estimating the surface temperature of avian eggs.