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A Parental Investment Study in Fish

In their study in parental care in fish, Mart R. Gross and R. Craig Sargent (1985) explain why a majority of fish have evolved male-only parental care strategies.  They use a cost-benefit analysis, identifying one benefit of parental care: the survival of the young and the expression the parent’s genes; and three costs of parental care: the cost of finding a mate, the cost of their own survival, and the cost of being able to produce more offspring in the future.  The benefit-the expression of their genes-is roughly the same for both males and females, as they both have roughly half of their genes expressed by their offspring.  For the male, the only real cost is the cost of finding a mate, but since many fish are territorial, this cost is not very heavy, and often nonexistent.  For females, the main cost is future fertility, which is a greater than the male’s cost of finding a mate. Gross and Sargent theorize that because the benefit of parental care is equal and because males have lower costs than females, males stand to increase their inclusive fitness by providing parental care and ensuring the survival of their young (Gross & Sargent 2005). It is important to note that a parental strategy like this would be hard for mammals because fertilization and pregnancy are internal as opposed to external, as in fish.

image from: http://www.flmnh.ufl.edu/fish/Gallery/Descript/SergeantMajor/SergeantMajor.html

~ by fknizner on .


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