We investigated the relationship between plasma and yolk oestrogens in laying female zebra finches (Taeniopygia guttata) by manipulating plasma oestradiol (E2) levels, via injection of oestradiol-17beta, in a sequence-specific manner to maintain chronically high plasma levels for later-developing eggs (contrasting with the endogenous pattern of decreasing plasma E2 concentrations during laying)...

Reproduction is influenced by many external factors. For egg laying of pond snails, one important trigger is the transfer from dirty, oxygen-poor water to clean, oxygen-rich water. This response is due to the combined effects of elevated oxygen level, chemical water composition and clean substrate. Whether this clean-water stimulus (CWS) resembles the natural egg-laying process has remained unt...

It has been hypothesized that parents increase their fitness by biasing the sex ratio of extra-pair offspring (EPO) towards males. Here, we report a male bias among EPO in a wild population of blue tits (Cyanistes caeruleus). This resulted from a decline in both the proportion of males and EPO over the laying order of eggs in the clutch. However, previous studies suggest that, unlike the declin...

The C. elegans egl-36 gene encodes a Shaw-type potassium channel that regulates egg-laying behavior. Gain of function [egl-36(gf)] and dominant negative [egl-36(dn)] mutations in egl-36 cause reciprocal defects in egg laying. An egl-36::gfp reporter is expressed in the egg-laying muscles and in a few other tissues. Expression of an egl-36(gf) cDNA in the egg-laying muscles causes behavioral def...

A 42-d study with 384 Hy-line brown laying hens was conducted to assess the effects of dietary octacosanol supplementation on laying performance, egg quality and blood metabolites of laying hens. Hens were randomly allocated into 4 dietary groups of 8 cages each, which were fed basal diet supplemented with 0 (Control), 9 (OCT9), 18 (OCT18), and 27 (OCT27) mg/kg diet of octacosanol isolated from...

In many forest passerine bird species, rapid climate warming has led to a phenological mismatch between the period of maximum nestlings' food requirements and the period of maximum food availability (seasonal caterpillar biomass peak) due to an insufficient advancement of the birds' laying dates. The initiation of laying is preceded by the development of the gonads, which in birds are regressed...

Suppression subtractive hybridization was used to detect differential expression of genes in the livers of laying and prelaying geese. Liver tissues from prelaying and laying geese were dissected for mRNA extraction. The cDNA, reverse transcribed from liver mRNA of prelaying geese, was subtracted from the cDNA generated from the laying geese (forward subtraction). Five hundred seventy-six clone...

Egg-laying behavior in the nematode Caenorhabditis elegans involves fluctuation between alternative behavioral states: an inactive state, during which eggs are retained in the uterus, and an active state, during which eggs are laid in bursts. We have found that the flp-1 gene, which encodes a group of structurally related neuropeptides, functions specifically to promote the switch from the inac...

Prostaglandin F (PGF) concentrations in the serum of laying and nonlaying hens and of cocks at various times during a day were measured by radioimmunoassay. The serum concentration of PGF was higher in laying hens than in nonlaying hens or cocks without regard to time of day. In all birds, the concentration showed a peak at 2 h after onset of light (0700 h). In laying hens on the day of laying ...

Pheasant eggs evaluated in the first period of egg-laying did not differ significantly in their weight and shape index and the values of both traits were, respectively, 30.7 to 32.2 g and 76.1 to 78.1%. Over the laying season the thickness of the shell decreased and its capacity for deformation and crush strength were greatest at the end of the laying season. The share of yolk in the egg was hi...