From beyond the grave, male Trinidadian guppies continue to reproduce. This isn’t a Father’s Day zombie love story though. Evolutionary biologists recently discovered that female Trinidadian guppies store reservoirs of sperm from long-dead guppy daddies for up to 10 months.

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Storing sperm could allow these guppy gals to be pioneers, settling new waters and giving birth to genetically diverse offspring. Females swim better than males, so the females can colonize new territory more easily.

“Populations that are too small can go extinct because close relatives end up breeding with each other and offspring suffer from inbreeding,” David Reznick, professor of biology at the University of California, Riverside and leader of the guppy study published in Proceedings of the Royal Society B, said in a press release. “If there are stored sperm, then the real population size is bigger than the number of animals you see. Also, stored sperm can increase genetic variation in other ways.”

Females live for up to two years, compared to the three to four month lifespan of a male. Keeping dead dads’ sperm on tap could allow females to give birth to a blast from the past male color pattern that will have all the other guppy girls going gaga. Female guppies are attracted to males with unusual patterns.

“In addition to learning about sperm storage, this is the first time we are learning about the huge differences in lifespan between males and females,” Reznick said. “If we were to use males to estimate generation time, then these differences mean that lucky females live for three generations. A human equivalent would be for us to have women around who were 90 years old and still very fertile.”

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Reznick noted that although long-term sperm storage seems rare in vertebrates, it may be that scientists simply haven’t observed it before. His team’s guppy observations span multiple generations and involve marking and recapturing the fish, as well as analyzing their genetic signatures. Guppy fathers from beyond the grave was an unexpected discovery from this extensive data gathering.

IMAGE: Male (left) and female (right) guppies (Wibowo Djatmiko, Wikimedia Commons)