A solitary female can spawn entire guppy populations

Biologists at the University of St Andrews and the University of the West Indies placed solitary females in multiple outdoor tanks (one in each tank).  In less than two years, almost every aquarium had thriving guppy populations ... all from one single female.  This is possible because female guppies can store sperm for many months.

Dr. Amy Deacon, the lead researcher at St Andrews, says:

"Our findings show that the guppy's range has expanded dramatically since the early 1900s.  Usually only one or a few fish are released. We know that the vast majority of species introduced to a new habitat in this way are unable to survive, let alone establish a population, which left us with a huge question mark."

"Sperm storage is an excellent adaptation for living in constantly changing habitats, and it might also explain the guppies' global success. Female guppies can store sperm in their reproductive tracts for many months after mating, and this enables single fish to establish populations even when no males are present.

"We also found that these populations kept all of the important behaviours that wild guppies have, so they would be well-equipped for surviving in a new environment."

In many parts of the world, guppies are used as mosquito control because guppies readily consume mosquito larvae which are laid on the surface of static water.  However, some guppies find their way into natural waterways due to rains, floods, or people simply disposing of their guppy-filled water into local waters.  In many places, these guppies have had a negative impact on native fish faunas.

Knowing that a single female guppy can spawn generations of guppies and colonize native waterways, we are once again reminded to practice responsible disposal of our aquarium livestock.  Whether it's one cup of sand, a piece of live rock, some unwanted plants, or just one lonely guppy, a single act of negligence can alter ecosystems forever.  Please be careful and conscientious aquarists from start to finish.

[via sTV]