In case you’re wondering, this is not about suing for child support!
Female Hermann’s are promiscuous: throughout their life, they have sex numerous times with different partners, and they can store sperm inside their bodies for three to four years. Now researchers in Italy want to find out whether this sperm storage affects fertilization.
You may be familiar with Hermann’s tortoises, since they are one of the most popular reptile pets in the U.S. That’s because they are small: females are typically larger than males, but even the largest female is usually only about 8 inches long; they are easy to care for, and they can live for many decades.
So how to determine who’s the father when there are multiple partners?
From the BBC:
Previous studies into similar species have found that a higher proportion of eggs are fertilised by the last mate.
“[This] ‘last in first out’ hypothesis was our main hypothesis,” said research team member Dr Sara Fratini from the University of Florence.
You have to love the terminology: “Last in, first out”!
That used to be the theory, but in a new study, “Influence of mating order on courtship displays and stored sperm utilization in Hermann’s tortoises,” Dr. Fratini and her colleagues were unable to find proof of this logic.
Instead, the team’s findings seem to indicate that the sperm are mixed up randomly inside the female’s storage tube, in a way that doesn’t relate to the time of their entrance.
What was their method? The team of experts gave paternity tests to offspring coming from 16 egg clutches, and found that how the sperm mixes inside the female’s storage tube was unrelated to the time of their arrival. They also determined that the greater the amount of a male’s sperm inside the female, the bigger his contribution to fertilization.
But there are still questions.
From the BBC:
But Dr Fratini said the findings could also suggest that females may actively optimise the use of stored sperm to use old sperm first – before it becomes unviable – and newly aquired sperm afterwards.
“At the present time, we cannot say which hypothesis is the real one,” Dr. Fratini told BBC Nature.
As for the debate about promiscuity in female Hermann’s tortoises, one obvious reason could be that the population of Hermann’s tortoises in the wild is dwindling, so the females have developed the ability to mate with several males and to store their sperm for a few years in order to ensure that their species will survive.
What do you think?
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