Characterization of structure and protein of vitelline membranes of precocial (ring-necked pheasant, gray partridge) and superaltricial (cockatiel parrot, domestic pigeon) birds

Abstract

Of all the known oviparous taxa, female birds lay the most diverse types of eggs that differ in terms of shape, shell pigmentation, and shell structure. The pigmentation of the shell, the weight of the egg, and the composition of the yolk correlate with environmental conditions and the needs of the developing embryos. In this study, we analyzed the structure and protein composition of the vitelline membrane (VM) of ring-necked pheasant, gray partridge, cockatiel parrot, and domestic pigeon eggs. We found that the VM structure is characteristic of each species and varies depending on whether the species is precocial (ring-necked pheasant and gray partridge) or superaltrical (cockatiel parrot and domestic pigeon). We hypothesize that a multilayer structure of VM is necessary to counteract the aging process of the egg. The multilayer structure of VM is only found in species with a large number of eggs in one clutch and is characterized by a long incubation period. An interesting discovery of this study is the three-layered VM of pheasant and partridge eggs. This shows that the formation of individual layers of VM in specific sections of the hen's reproductive system is not confirmed in other species. The number of protein fractions varied between 19 and 23, with a molecular weight ranging from 15 to 250 kDa, depending on the species. The number of proteins identified in the VM of the study birds' eggs is as follows: chicken-14, ring-necked pheasant-7, gray partridge-10, cockatiel parrot-6, and domestic pigeon-23. The highest number of species-specific proteins (21) was detected in the VM of domestic pigeon. This study is the first to present the structure and protein composition in the VM of ringnecked pheasant, gray partridge, cockatiel parrot, and domestic pigeon eggs. In addition, we analyzed the relationship between the hatching specification of birds and the structure of the VM.

Structural and proteomic analyses of vitelline membrane proteins of blackbird (Turdus merula) and song thrush (Turdus philomelos)

“…They demonstrated that the cognition of species-specific proteins that are likely to be associated with the adaptation of birds to different environmental stimuli maybe a suitable tool to replace DNA analysis. Similar conclusions were drawn by Damaziak et al 11 who analyzed the possibility of occurrence of species-specific proteins in the VM depending on their breeding and hatching specifications. It was also shown that the structure of VM differs between different bird species 11 – 13 .…”

“…They demonstrated that the VM of chicken eggs is made exclusively of different thicknesses fibers, whereas in ducks, there are additionally strongly flattened elements called sheets. Further research using SEM and TEM allowed to find specific structures combining layers of IL and OL in the VM of emu 13 and an untypical VM formed from 9 rather than 3 layers in eggs of ring-necked pheasant and gray partridge 11 . It is unknown what are the functions of these morphological elements of the VM.…”

“…However, their occurrence in different forms in different species of birds can be used for identification and opens a new important direction of research for bird biology. Out of 18,043 currently known bird species 21 , the analysis of the VM structure was carried out only for several 3,7,[10][11][12][13][14][15][16][17] . Damaziak et al 11 were the first and only ones to describe the results of the analysis of the VM structure of two altricial species (cockatiel parrot and pigeon), a group of birds with the same hatching specification as blackbird and song thrush.…”

“…A previous study by Mann 18 also did not confirm the presence of these proteins in chicken VM. Damaziak et al 11 isolated U3JXV8 FICAL protein from the VM of cockatiel parrot, but it was not found in the pigeon VM. In this study, the presence of U3KEZ1 FICAL protein was confirmed for the first time as a component of VM of birds.…”

“…Mann 18 confirmed the presence of 137 other proteins in the whole VM of a chicken egg. However, subsequent investigations have shown the significant differences in the structure and composition of proteins of chicken and duck egg yolks VM 12 , selected ratites 13 , and birds belonging to the precocial and superaltrical species 11 . Therefore, in this study, we hypothesized that structural and proteomic elements of VM of egg yolk are species-specific as similarly egg shape 19 and shell pigmentation 20 .…”