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A comparative study of sperm-egg interactions in birds
T R Birkhead1, B C Sheldon, F Fletcher
1Department of Animal and Plant Sciences, University of Sheffield, UK.
Journal of Reproduction and Fertility
|July 1, 1994
Summary
Spermatozoa interaction with bird eggs varies greatly by species and ovum size. More trapped sperm correlates with more penetrated sperm, indicating sperm usage rates from storage tubules.
Area of Science:
- Reproductive Biology
- Avian Ecology
- Sperm-Egg Interaction
Background:
- Understanding avian reproduction requires examining sperm-egg interactions.
- The perivitelline layer plays a crucial role in fertilization in birds.
Purpose of the Study:
- To compare sperm interaction with the perivitelline layer across 27 bird species.
- To investigate the relationship between ovum size and sperm penetration.
- To analyze sperm distribution patterns on and within the egg.
Main Methods:
- Comparative analysis of spermatozoa on outer and inner perivitelline layers.
- Quantification of trapped spermatozoa and penetration holes.
- Correlation analysis between sperm numbers, ovum size, and sperm distribution.
Main Results:
- Total spermatozoa per egg ranged from 29 to 164,000, positively correlated with ovum size.
- Spermatozoa formed a 'halo' around the germinal disc, especially in passerines.
- Trapped sperm numbers positively correlated with inner perivitelline layer holes across species.
Conclusions:
- Spermatozoa interaction with the perivitelline layer is species-specific and influenced by ovum size.
- Sperm usage rates can be inferred from changes in sperm numbers across a clutch.
- Proteolytic activity may create artifactual holes in the perivitelline layer.