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Intra-ejaculate sperm selection in female zebra finches
N Hemmings1, C Bennison2, T R Birkhead2
1Department of Animal and Plant Sciences, University of Sheffield, Alfred Denny Building, Western Bank, Sheffield, UK n.hemmings@shef.ac.uk.
Biology Letters
|June 10, 2016
Summary
Sperm that fertilize eggs are not random. In birds, successful sperm have less variation in shape, smaller heads, and longer tails compared to all sperm inseminated.
Area of Science:
- Reproductive biology
- Animal reproduction
- Sperm morphology
Background:
- Few sperm survive the journey to fertilize an ovum.
- The characteristics of the 'fertilizing set' of sperm are not well understood.
Purpose of the Study:
- To investigate if oviductal selection in birds produces a morphologically distinct subset of sperm.
- To determine the characteristics of sperm that successfully reach the ovum.
Main Methods:
- Examining sperm trapped by the perivitelline layer of the ovum in birds.
- Comparing the morphology of fertilizing sperm with inseminated sperm.
Main Results:
- Sperm reaching the ovum exhibited significantly lower morphological variation.
- Fertilizing sperm had smaller head size and greater tail length compared to inseminated sperm.
Conclusions:
- Oviductal selection in birds favors sperm with specific morphological traits.
- Sperm morphology, not just tail length, is crucial for successful ovum fertilization.
