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.