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Effect of Acclimation Salinity on Fertilization Success in the Mummichog, Fundulus heteroclitus

Robert E. Palmer and Kenneth W. Able
Physiological Zoology
Vol. 60, No. 5 (Sep. - Oct., 1987), pp. 614-621
Stable URL: http://www.jstor.org/stable/30156136
Page Count: 8
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Effect of Acclimation Salinity on Fertilization Success in the Mummichog, Fundulus heteroclitus
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Abstract

Fertilization success and sperm motility were tested in fresh water, 15, and 30 ppt salt water (<5, 500, and 1,000 mOsm/kg, respectively) for a population of Fundulus heteroclitus maintained at ambient salinity (30 ppt) and later acclimated to fresh water in the laboratory to determine the effect of the adult's acclimation salinity on reproductive success in different salinities. The same parameters were measured for individuals from a natural freshwater population. Individuals maintained in 30 ppt were unable to fertilize eggs in fresh water (0%), while fertilization success in 500 and 1,000 mOsm/kg was approximately 80%. Acclimation to fresh water enhanced fertilization success in fresh water (mean 41%). Females acclimated to fresh water had a significantly lower (P < .05) ovarian osmolarity, which may be related to the observed increase in fertilization success. A natural freshwater population had a fertilization rate in fresh water of 72%, which suggested that the period of laboratory acclimation (5 wk) was not sufficient for complete acclimation of the gametes. While enhanced fertilization success in fresh water was observed in the laboratory for adults acclimated to fresh water, these same individuals had diminished success in 1,000 mOsm/kg. Both the natural freshwater population and the laboratory population acclimated to fresh water had 80% success in 500 mOsm/kg; however, they were unable to fertilize eggs in 1,000 mOsm/kg, apparently because of sperm immotility. Thus for F. heteroclitus there is a restricted salinity range over which gametes are viable. Irrespective of acclimation salinity, optimum success occurs in 500 mOsm/kg, which is closest to the internal osmolarity of the fish.

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