In vitro formation of holes on the inner perivitelline layer of quail ovum by chicken spermatozoa

Modification and Clinical Application of the Inner Perivitelline Membrane Test in Different Avian Species

The aim of this study was to adapt an inner perivitelline membrane (IPVM) test as an interspecies penetration assay for avian spermatozoa. The IPVM of different bird species was evaluated to test the penetrating ability of avian spermatozoa in an intra- and interspecies design. Isolation of the IPVM via acid hydrolysis was tested in pre-incubated chicken eggs and in six other avian species. The separation protocol was modified (time, acid concentration) to facilitate practicability. Separated membranes were evaluated with dark field microscopy for the presence of holes produced by penetrating spermatozoa. In chicken eggs, the influence of different membrane storage conditions was tested. In the penetration assay, the IPVM of chicken eggs was used as a model for fresh and frozen-thawed rooster sperm and for fresh spermatozoa of cockatiels and falcons. Results demonstrated that the time of egg-incubation had a significantly negative influence on the isolation ability of the IPVM (p < 0.0001). IPVM-separation was successful for a maximum of two days after preincubation. In the experiments with eggs from other avian species, results were heterogenous: there was no isolation in geese and cockatiels, 20% in the European kestrel, and 40% in pheasant, quail, and duck. In the penetration assay, holes were found in 100% of the IPVM of chicken eggs after incubation with native and frozen-thawed rooster semen and in 10% with fresh cockatiel semen. Falcon spermatozoa failed to produce visible holes. In conclusion, the IPVM of chicken eggs seems to be unsuitable to establish a functional sperm assay in other species tested but is suitable for quality evaluation of cryopreserved rooster sperm.

Characterization of the sperm-associated body and its role in the fertilization of the chicken Gallus domesticus

The present paper aimed to characterize the substance forming the sperm-associated body (SB), to find its producing sites, and to show its functions in the fertilization of chicken. The SB was found both in between the inner and outer layers of vitelline membranes around eggs and in the oviductal infundibulum. Material from which the SB is constructed (SB substance) was isolated from the vitelline membranes. It was a hydrophobic protein with a molecular size of 570 kDa. X-ray microanalysis detected calcium in the aggregates of the SB substance. Immunofluorescence and immunoelectron microscopy showed that the substance was produced in secretory cells in the luminal epithelium of the oviductal infundibulum and was provided to the egg on and in its vitelline membrane. During incubation, the SB substance bound with spermatozoa in the posterior portion of their flagella. Holes and disks were found in the vitelline membranes of fertile eggs at a ratio of 1: 19-24. Over 94% of the holes were accompanied by SB. The presence of SB is necessary for fertile spermatozoa to make holes in the membrane and to enter the fertile egg.

Sperm-egg interaction is mediated by a sperm-associated body in quail

The present study describes the holes in the inner vitelline membrane of fertile eggs of the quail Coturnix japonica, which remain after the spermatozoa pass through. It was shown that the light-microscopically observable 'holes' correspond mostly to electron-microscopically defined 'disks', and, to a lesser extent (about 5%), real holes. Immunofluorescent staining of the vitelline membranes with an antiquail ZPC antiserum was used to discriminate the holes from the disks light-microscopically. Over 96% of holes were accompanied by calcium-coated sperm-associated bodies, indicating a close relationship between the two. There was no preferential localization of the disks, holes or sperm-associated bodies in the vitelline membrane around the egg. The sperm-associated bodies bound with the spermatozoa at the posterior end of sperm flagella. Incubation of the inner vitelline membranes, isolated from the largest follicles, with spermatozoa resulted in production only of the disks, whereas the holes (about 9%) were produced when the sperm-associated bodies were added to the system. It was suggested that the sperm-associated bodies assist fertile spermatozoa in binding to the inner vitelline membrane, making holes in the membrane and passing through them in fertile eggs.