For the sea snail Goniobranchus reticulatus (formerly known as Chromodoris reticulata), sex is literally “disposable”. In a 2013 study, this species became the first known animal to reproduce using a “disposable penis”, which it discards after mating and can regenerate its penis within 24 hours; but this ability is not unlimited.
It appears that these sea slugs have at least two other “spare” penises, stored internally. This animal can regenerate its penis in about 24 hours after the previous one is lost.
In the animal world, competition for reproduction has led to the development of penises with amazing shapes, often equipped with spiny structures designed to remove the sperm of rivals. The same is true for these sea snails.
However, efficiency in eliminating rival sperm comes with the risk of damaging one’s own organ. Therefore, having a new penis ready to use after losing the old one is a smart strategy to maximize the chances of reproduction.
A sea snail can regenerate its penis in 24 hours
“These snails offset the short-term cost of reduced reproductive opportunities caused by penis loss by the reproductive advantage gained by removing sperm in the context of intense competition,” wrote the authors of the study, published in Biology Letters.
“Also, they reduce this time frame by using a spiral structure that allows the next penis to be prepared quickly. Thus, the disposable penis provides an example where sexual selection is as important for simultaneous hermaphrodites as it is for separate-sex species,” the researchers write.
If you’re wondering “that’s a weird male tactic, but what do the females do?”, it should be noted that in this species, all individuals discard their penises after mating. That’s because each partner is simultaneously hermaphrodite, having both male and female genitalia. During copulation, both partners insert their penis into the other’s vagina, and at the end, each gives up the organ used and moves on, explains IFL Science.
While it seems extreme to lose body parts after mating, there are species of sea slugs that take this ability to another level. Some practice self-decapitation, leaving only the head, which, in an amazing act, survives several days without a body before regenerating a new one.
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Source: www.descopera.ro
