. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 13kV FIGURE 8. An ovum fixed 3 min after insemination in 30%o salinity. Total blockage of the micropyle (M) has occurred. (Magnification X3600) population lives in a less than full strength sea water habitat (20-25%o), and produces viable offspring at varying salinities. The PC population (~20%o) however, could not produce viable offspring at 30%o salinity. Holliday (1971) reported that crossfertilization between the races offish species results in responses characteristic of the female parent. In our observations, cross- fe
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 13kV FIGURE 8. An ovum fixed 3 min after insemination in 30%o salinity. Total blockage of the micropyle (M) has occurred. (Magnification X3600) population lives in a less than full strength sea water habitat (20-25%o), and produces viable offspring at varying salinities. The PC population (~20%o) however, could not produce viable offspring at 30%o salinity. Holliday (1971) reported that crossfertilization between the races offish species results in responses characteristic of the female parent. In our observations, cross- fertilization between the two populations similarly resulted in a response to salinity that was characteristic of the origin of the female. The ability of sperm to fertilize ova was not affected by the salinities tested. Brummett and Dumont (1979) found that activation of the Fundulus heteroclitus ovum by fertilization is followed by formation of a block to polyspermy in the form of a "fertilization plug" consisting of numerous globules of various sizes. It would follow that if a type of "plug" were formed upon artificial activation, it would also prevent access of sperm to the ovum and would render such ova unfertilizable. From SEM views of the micropyles it is clear that upon artificial activation the micropyle becomes blocked with globular, particulate, or fibrillar particles. There seems to be no definite correlation between the type of block and whether the egg has been artificially activated. We are unsure why 40% of the eggs which were uninseminated in 15%o had micropylar blocks when experimental data indicate that they are almost all fertilizable. It is possible that the fixative could have activated some of the eggs. Brummett and Dumont (1979, 198la) have shown that cortical vesicle break- down and extrusion of the contents begins to occur one second after insemination. They examined the contents of these vesicles, finding large (9 yu) and small (
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
