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2015 ; 282
(1818
): 20151682
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Polyspermy in birds: sperm numbers and embryo survival
#MMPMID26511048
Hemmings N
; Birkhead TR
Proc Biol Sci
2015[Nov]; 282
(1818
): 20151682
PMID26511048
show ga
Polyspermy is a major puzzle in reproductive biology. In some taxa, multiple
sperm enter the ovum as part of the normal fertilization process, whereas in
others, penetration of the ovum by more than one sperm is lethal. In birds,
several sperm typically enter the germinal disc, yet only one fuses with the
female pronucleus. It is unclear whether supernumerary sperm play an essential
role in the avian fertilization process and, if they do, how females regulate the
progression of sperm through the oviduct to ensure an appropriate number reach
the ovum. Here, we show that when very few sperm penetrate the avian ovum,
embryos are unlikely to survive beyond the earliest stages of development. We
also show that when the number of inseminated sperm is limited, a greater
proportion than expected reach and penetrate the ovum, indicating that females
compensate for low sperm numbers in the oviduct. Our results suggest a functional
role for supernumerary sperm in the processes of fertilization and early
embryogenesis, providing an exciting expansion of our understanding of sperm
function in birds.
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