Hydrolysis of the Hen’s Perivitelline Layer by Cock Sperm in vitro

Bakst, M. R.; Howarth, B.

doi:10.1095/biolreprod17.3.370

Cited by 104 publications

(69 citation statements)

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“…The initial stage of avian fertilisation involves the penetration of the inner pervitelline layer (IPVL; analogous to mammalian zona pellucida) by multiple sperm. Multiple sperm then enter into the cytoplasm of a germinal disc (Bakst and Howarth 1977;Birkhead et al 1994;Okamura and Nishiyama 1978a;Okamura and Nishiyama 1978b;Tarin and Cano 2000). In chicken, [100 sperm can enter an ovum without resulting in decreased fertility (Bramwell et al 1995).…”

Section: Discussionmentioning

confidence: 99%

Adaptive Evolution of Gamete-Recognition Proteins in Birds

Berlin

Ellegren

2008

J Mol Evol

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Gamete-recognition proteins have been shown to evolve by positive selection in diverse organism groups, such as marine invertebrates and mammals, although underlying evolutionary mechanisms driving this rapid divergence are poorly understood. However, several hypotheses have been put forward to explain the observed pattern, including different forms of sexual conflict and sperm competition. Because female gametes require more energy to produce than male gametes, female organisms suffer more when fertilisation goes wrong. One process that results in a failed mammalian fertilisation is polyspermy, when [1 sperm fertilises the egg. However in birds, there is no such sexual conflict because multiple sperm typically bind and fuse with the egg. If sexual conflict driven by polyspermy avoidance is important for the evolution of gamete-recognition proteins in vertebrates, we expect to find positive selection in the genes to be less pronounced in birds. We therefore sequenced six genes (ZP1, ZP2, ZP4, ZPAX, CD9, and Acrosin) encoding gamete-recognition proteins in several bird species to test for positive selection. For comparison, we also analysed ortologous sequences in a set of mammalian species. We found no major differences in the occurrence of adaptive evolution and the strength of selection between bird and mammal orthologs. From this we conclude that polyspermy avoidance does not act as the main underlying evolutionary force shaping the rate of evolution in these genes. We discuss other possible processes that could explain positive selection of gamete-recognition proteins in birds and mammals, such as hybridisation avoidance, cryptic female choice, and postcopulatory sperm competition.

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Section: Discussionmentioning

confidence: 99%

Adaptive Evolution of Gamete-Recognition Proteins in Birds

Berlin

Ellegren

2008

J Mol Evol

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“…Fertilization of the ovum takes place in the infundibulum of the oviduct (Olsen and Fraps, 1944). Spermatozoa bind to the inner periviteline layer (IPVL) and undergo the acrosome reaction (Bakst and Howarth, 1977). Acrosomal enzymes that hydrolyse the IPVL are released and spermatozoa are able to enter the ovum through holes created by these enzymes (Howarth and Digby, 1973).…”

Section: Sperm Qualitymentioning

confidence: 99%

The chicken embryo and its micro environment during egg storage and early incubation

Reijrink¹,

Meíjerhof²,

Kemp

et al. 2008

World's Poultry Science Journal

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When egg storage periods are prolonged (>7 days), hatchability and chick quality declines. The reason for this decline has been investigated, but is still not completely understood. At oviposition the developmental stage of the chicken embryo varies and so do the total number of viable cells. During storage, changes can occur in the embryo. Embryo viability at the end of storage seems to be dependent on the number of viable cells and the developmental stage of the embryo at oviposition. When the hypoblast is completely formed (during the quiescent developmental stage), the embryo seems to be more able to endure prolonged storage periods than embryos that are less or more advanced. During storage, changes also occur in egg characteristics such as albumen viscosity, albumen pH and yolk pH. There appears to be an interaction between albumen pH and embryo viability during early incubation and perhaps also during storage. An albumen pH of 8.2 seems to be optimal for embryo development. Albumen pH may influence embryo viability, but embryo viability may in turn, affect albumen pH. It has been hypothesised that an embryo in which the hypoblast is completely formed is better able to provide an effective barrier between the internal embryo and the exterior (yolk and albumen) and/or is better able to produce sufficient amount of carbon dioxide, which will reduce the pH level in the micro environment of the embryo to the optimal pH of 8.2. It appears that, to maintain hatchability and chick quality after prolonged storage periods, embryonic development should be advanced to the stage in which the hypoblast is completely formed or the atmosphere during storage and early incubation should be altered in such a way that albumen pH is maintained at the optimal level of 8.2.

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“…Birkhead [19] observed that the number of sperm trapped in the outer PL is positively correlated with the size of the ovum and is likewise correlated with the number of sperm that have penetrated the inner PL. Interestingly, the sperm trapped in the outer PL retain an intact acrosome [20][21]. If fertilized, the first cleavage furrow in the GD appears 7-8 hr post-ovulation, while the egg-mass is in the isthmus.…”

Section: Oviductmentioning

confidence: 99%