As humans, we think of reproduction in the traditional sense. But scientists discovered a fish with genes of only its father, which means that a male fish produced a clone of itself. This is a  very rare phenomenon called androgenesis.

The fish that produced a clone of itself is a hybrid called the squalius alburonides that typically lives in Portugal and.Spain . The fish belongs a hybrid complex, a group of organisms with multiple parental combinations that can mate with each other. It is believed that the hybridization occurred between females and males of another species called anaecypris. To sustain its population, the squalius mates with others closely related to its lineage.

“Mostly animals have sex cells containing only one chromosome set, which means the egg and sperm are both required for reproduction. But in squalius alburnoides, sperm with multiple chromosome sets can provide all the nuclear genetic material needed for a viable offspring — paving the way for androgenesis” (Yin, 2017).

A graduate student, Mr. Morgado-Santos,  at the University of Lisbon said that Androgenesis could happen when a spermicide fertilizes an egg that does not contain chromosomes or when the genetic content from the egg is destroyed after fertilization. He and his group conducted an experiment by putting male and female squalius alburnoides with males and females of mother squalius alburnoides in an artificial pond and let the fish reproduce. Genetically analyzed offspring revealed that of the 100 samples, one of the offspring had only paternal chromosomes.

One instance in a 100 is a rare occurrence, but it shows that reproduction can occur via androgenesis.

Yin, Steph, “Somehow, This Fish Fathered a Near Clone of Itself,” the New York Times, May 2017.


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