Incubation

About: Incubation is a research topic. Over the lifetime, 5748 publications have been published within this topic receiving 126541 citations.

The onset of incubation in birds

Abstract: Birds vary between and within species in the moment at which they begin incubation of a clutch. The timing of incubation in birds can have important effects on fitness and thus an adaptive explanation has seemed warranted. The most prominent of the several which have been offered is Lack's (1954) brood reduction hypothesis. More recently, we outlined a nest failure hypothesis (Clark and Wilson 1981) and showed that it was supported by existing data for small altricial birds. In this paper, we reply to Richter's (1982) critique of the nest failure hypothesis and further explore the problem of assessing the costs and benefits of incubating before a clutch is complete. First, we briefly review the logic of the general problem. One effect of incubating before the last egg is laid is hatching asynchrony and the production of offspring that are younger, and therefore smaller, than their nestmates. Lack (1954) proposed that this size asymmetry is itself an adaptation to facilitate brood reduction when food becomes suddenly scarce. If equally matched nestmates compete for insufficient food, they may all receive too little and all have reduced chances for survival as nestlings or fledglings. If some nestmates are smaller, however, these are likely to starve quickly while the others receive adequate food. Another possible purpose of early incubation is to minimize the potential for total nest failure, usually by predation. A clutch on which incubation is initiated sooner will have at least some young ready to fledge sooner, as observers have often noted (e.g., Marchant 1960). A nest that is destroyed after the first offspring fledges, but before the last, is at least partially successful. If incubation had been postponed, the same nest would have been a total loss. This interpretation suggests that early incubation serves to decrease the time spent in the nest by first eggs or offspring. Size and age differences among nestlings are a by-product of the adaptation, and mortality from these differences is a cost. We (Clark and Wilson 1981) built a specific model of the nest failure hypothesis, and tested it with data from 87 altricial bird species. We also reexamined the brood reduction hypothesis. Our conclusions can be briefly summarized as follows. 1. Most small altricial birds begin incubation before the last egg is laid; in contrast, proponents of the brood reduction hypothesis give an impression of general hatching synchrony.

Respiratory Acidosis and Eggshell Resorption by the Chick Embryo

Abstract: Eggs of the domestic fowl were injected with 45 Ca and then subjected to normal incubation or to incubation in 9% carbon dioxide in air. The embryos, yolk, albumen and shell were analysed at various times after incubation had started. The results demonstrate that there is normally a resorption of the eggshell during the latter part of incubation but that this process is depressed by hypercapnia. The results are discussed in relation to the events in normal development and in relation to possible mechanisms of shell resorption.

Hepatitis E virus infection in pregnant rhesus monkeys.

Abstract: Ten non-pregnant female monkeys and four pregnant monkeys (all Macaca mulatta) in the last third of their gestation period were infected intravenously with the stool sample of a patient with hepatitis E virus infection (immuno-electronmicroscopy positive for hepatitis E virus) Four more non-pregnant monkeys were inoculated with a lower dose (less number of virus particles by IEM) of a stool sample collected on a different day from the same patient The average incubation period as evidenced by the rise of serum alanine transferase in the non-pregnant monkeys, was 364 +/- 49 days The dose of the virus did not affect the incubation period Two of the pregnant monkeys had incubation periods of 9 and 13 days respectively They delivered healthy babies on 40th and 53rd day respectively after inoculation At the age of 11 months, both babies were negative for anti-HEV antibodies One monkey which delivered a healthy baby on the 2nd day after inoculation had incubation period of 36 days The baby of this monkey was anti-HEV positive at the age of 11 months The incubation period was 41 days in the fourth monkey which delivered a macerated foetus on the 36th day after infection No fatality was recorded in the infected monkeys Bile samples collected from all monkeys showed strong signals in nested polymerase chain reaction (PCR) It seems that the incubation period in pregnant monkeys was determined by the state of pregnancy

In vitro activation of cellular immune response to gross virus-induced lymphoma

Abstract: Spleen cells from W/Fu rats 40 days or more after immunization with a syngeneic Gross virus-induced leukemia were unreactive in direct cytotoxic assays Incubation of these immune cells at 37°C for 12 hr or longer, in the absence of antigen, resulted in the appearance of specific cytotoxic reactivity Other lymphoid cells from the immune rats also were activated upon in vitro incubation, but to a lesser extent Experiments were performed to define the necessary conditions and the mechanism for the in vitro incubation Activation was temperature dependent, occurring at 37°C but not at 4°C Immune serum suppressed the activation, but normal rat serum also had some inhibitory activity Passage of immune cells through a nylon column, before preincubation, prevented activation In contrast, exposure to nylon after preincubation did not remove cytotoxic reactivity These findings demonstrate the reversal of a central inhibition of immune cell activity The explanations offered for this phenomenon included change in surface characteristics of the immune cells during in vitro incubation, and the possible need for an adherent helper cell