mercoledì 7 marzo 2007

All’ultimo pedipalp

Ieri sul New Scientist è stata riportata una ipotesi esplicativa di un comportamento aracnoide molto interessante.
‘Chastity belts’ block rival sperm in female spiders.

Some male spiders up-and-leave right after sex for good reason – they risk being eaten by their female partners if they linger too long. In the process of making a swift exit, many leave part of their genitalia inside their mates.
Now a new study reveals that detaching part of the genital organ is not a means to help the male escape a murderous attack. Instead, the abandoned genitals act as “chastity belts” and block the entry of sperm from competitors into the female.
Gabriele Uhl at the University of Bonn, Germany, and colleagues watched wasp spiders (Argiope bruennichi) mate. During the act, a male must insert one of its two sperm-carrying organs, known as pedipalps, into the female’s genital openings. After delivering the sperm, the tip of the pedipalp becomes stuck inside the female, forming a plug in her reproductive tract.
To find out if leaving behind part of the pedipalp helped the males escape death, researchers compared the damage to this organ during first-time sexual encounters with damage sustained in subsequent encounters.
Ripensando a recenti dichiarazioni, non ho potuto fare a meno di chiedermi se il binettiano cilicio possa avere questa funzione, e soprattutto chi ha perso il proprio pedipalp...

(Fotocomposizione di Alessandro Capriccioli.)

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