The Amazon Molly

The Amazon Molly

There exists in Central America a race of female fish that survives almost entirely without males. Their lifestyle recalls the legendary Amazons of Ancient Greece — women so strong that only the most skillful of male warriors could hold their own against them.

The Amazon molly, Mollienisia formosa, is closely related to the guppy and is no larger than a man's finger. This race of female fish never gives birth to males and must "borrow" males of a closely related species for purposes of conception. This happens only once a year, as is did among the Amazons of Greek legend.

The sperm of the male does not actually fertilize the eggs of the molly. It does penetrate the egg cell, but only to activate cell division. By this process a single cell will develop into the billions of cells that compose a living creature. As soon as the process is initiated, the sperm degenerates without fusing with the egg nucleus.

Because of the degeneration of the sperm, none of the hereditary traits contained in the sperm can possibly be inherited by the young. This is quite different from the young of most other species, for when the sperm fuses with the egg the offspring inherit traits from both parents. In the case of the Amazon molly it could be said the male chromosomes are murdered in the female cell. This also recalls the legend of the Homeric Amazon women, who supposedly routinely destroyed any male offspring.

The method of reproduction of the Amazon molly is a very specialized form of parthenogenesis — birth without fatherhood — known scientifically as hynogenesis. A strange brood of young is produced as a result of this unusual conception. Born into the world are only females, identical down to the last scale, each an exact clone of the mother. All have inherited exactly the same traits, since there has been no mixture of genes that they could have inherited from the father. Down through the millennia each generation has remained identical to all those that preceded it.

The lifestyle of the Amazon molly clearly shows what human life would be like if both sexes were not actively involved. The fish have no individuality. This race of females is not a primitive form of fish, as might easily be concluded; on the contrary, it is quite an advance form of life, highly specialized to preserve the race. As already stated, the molly is closely related to the guppy, a family of fish that gives birth to its young alive. All males in this family are cannibalistic. When a females starts to give birth, the male swims under the female, swallowing the young as rapidly as they are born.

Perhaps the cannibalism of the male guppy serves as a rather barbarous method of birth control, thereby preventing overpopulation and its consequences. Nevertheless, the female aims to prevent the loss of her brood and must find a hiding place to produce her young. This becomes rather difficult when the fish population of an area is high, which it often is.

The threat of cannibalism has been overcome by the Amazon molly. It has its own territory and leaves it only temporarily to mate with the selected species of males. This completed, the female returns to her territory. If the male tries to follow, she rams and beats him with her fins until he is driven away. As a result, no male ever enters the realm of the Amazon molly.

The life of the Amazon molly illustrates how an animal society can exist without a mixture of genetic material. Being clones of one another, generations of mollies possess no individuality. In a human society the loss of uniqueness would be a tragic nightmare. For the Amazon molly, their sameness is efficient, purposeful, and trouble—free.

From the book: 
Our Fascinating Earth