The genitalia of Callosobruchus
March 13th 2009 07:46
Callosobruchus is a genus of beetles known for their genitalia, which include some very unpleasant looking pieces of kit. The sexual organs of males are covered in spines, and these are used to cling onto females during copulation.
A new study by Cosmia Hotzy and Goran Arnqvist of Uppsala university in Sweden has shown that males with the longest spines do best in terms of reproductive success, though at the cost of damage to females. The reproductive tracts of females suffer scarring as a result of these forceful copulations, but they have evolved a way of minimising the effects of this damage, namely by having thicker cuticles in the tract. Males don't appear to gain any advantage from causing harm per se; rather, it's that harm is a side-consequence of having these spines. Those males that can cling onto females for longer have a better chance of fertilising her eggs.
Read more about these amazing animals in this National Geographic article.
Sexual conflict is actually quite common in the animal kingdom, and it is a huge area of current research. While the genders have a common stake in producing viable offspring, they will often differ as to how much investment is optimal for them to contribute. When such asymmetries arise, conflict results, and it can be manifested in a multitude of ways. These beetle genitalia are one example, but there are many others.
Spines on the phallus of C. maculatus. Image from National Geographic
A new study by Cosmia Hotzy and Goran Arnqvist of Uppsala university in Sweden has shown that males with the longest spines do best in terms of reproductive success, though at the cost of damage to females. The reproductive tracts of females suffer scarring as a result of these forceful copulations, but they have evolved a way of minimising the effects of this damage, namely by having thicker cuticles in the tract. Males don't appear to gain any advantage from causing harm per se; rather, it's that harm is a side-consequence of having these spines. Those males that can cling onto females for longer have a better chance of fertilising her eggs.
Read more about these amazing animals in this National Geographic article.
Sexual conflict is actually quite common in the animal kingdom, and it is a huge area of current research. While the genders have a common stake in producing viable offspring, they will often differ as to how much investment is optimal for them to contribute. When such asymmetries arise, conflict results, and it can be manifested in a multitude of ways. These beetle genitalia are one example, but there are many others.
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