Evolution of sex-biased maternal effects in birds: I. Sex-specific resource allocation among simultaneously growing oocytes.
J Evol Biol
; 17(6): 1355-66, 2004 Nov.
Article
em En
| MEDLINE
| ID: mdl-15525420
ABSTRACT
Females in species that produce broods of multiple offspring need to partition resources among simultaneously growing ova, embryos or neonates. In birds, the duration of growth of a single egg exceeds the ovulation interval, and when maternal resources are limited, a temporal overlap among several developing follicles in the ovary might result in a trade-off of resources among them. We studied growth of oocytes in relation to their future ovulation order, sex, and overlap with other oocytes in a population of house finches (Carpodacus mexicanus) where strongly sex-biased maternal effects are favoured by natural selection. We found pronounced differences in growth patterns between oocytes that produced males and females. Male oocytes grew up to five times faster and reached their ovulation size earlier than female oocytes. Early onset and early termination of male oocytes' growth in relation to their ovulation resulted in their lesser temporal overlap with other growing ova compared with female oocytes. Consequently, ovulation mass of female but not male oocytes was strongly negatively affected by temporal overlap with other oocytes. In turn, mass of male oocytes was mostly affected by the order of ovulation and by maternal incubation strategy. These results provide a mechanism for sex-biased allocation of maternal resources during egg formation and provide insights into the timing of the sex-determining meiotic division in relation to ovulation in this species.
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Base de dados:
MEDLINE
Assunto principal:
Oócitos
/
Reprodução
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Processos de Determinação Sexual
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Tentilhões
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Evolução Biológica
Idioma:
En
Ano de publicação:
2004
Tipo de documento:
Article