ORAL SEX IN SPIDERS

When we think about sexual rituals in insects, perhaps the first things that come to mind are sexual cannibalism of males by females, nuptial gifts from males to females, opportunistic mating, pair bonding, genital mutilation, or plugging. All of these, while impressive, are relatively well documented.

But, in 2016, Gregoric and colleagues studied the sexual behavior of the Darwin's bark spider from Madagascar. Among the rituals in the diverse and striking sexual repertoire of this species, researchers documented the occurrence of oral sex. That's right! Males of this species obligatorily secrete oral fluids (saliva) into the female genitalia before, during, and after copulation. How’s that for a socially transferred material!

The exact behavioral and adaptive significance of oral contact in the sexual repertoire of the Darwin's bark spider, is yet to be understood. However, the researchers point to two plausible functions of this behavior. By mechanisms of cryptic choice, females might assess male quality and bias the fertilization of their gametes to favor paternity with sperm from better quality males. Another hypothesis suggests that in order to reduce sperm competition, salivary enzymes might induce some sort of physiological advantage to the donor's sperm over the sperm of rivals. However, It is necessary to decipher the composition of male spider saliva before we can determine the significance of this behavior as well as how often it occurs among spiders, or even other animals.

Here you can watch a video of this behavior, posted by the Evolutionary Zoology Lab: https://www.youtube.com/watch?v=_Zp4-tjha6M. It shows the complete behavior, including the transfer of liquid into the female genitals!!!

Source:

Gregorič M, Šuen K, Cheng RC, Kralj-Fišer S & Kuntner M. (2016). Spider behaviors include oral sexual encounters. Scientific Reports 6, 25128. doi.org/10.1038/srep25128