Marie Curie Actions: Inspiring Researchers - Imdea

Castration,cannibalism andconflict: the battle ofthe sexes, spider-styleThere are about 40 species of nephilid spider scattered acrossthe tropical and sub-tropical regions of the Americas, Africa,Asia and Australia. They include the golden orb weavers whosewebs can reach 1.5 metres in diameter. However, what reallymakes the nephilids stand out is the massive size differencebetween the sexes; the females are 10 to 100 times heavierthan the males. This means that males vastly outnumberfemales, because few females survive long enough to reachtruly gigantic proportions.Although many aspects of nephilid biology have been studiedextensively in the past, little was known about their matinghabits – until Matjaž Kuntner came along, that is. Originally fromSlovenia, he spent six years working at the prestigious SmithsonianInstitution in the US before a Marie Curie Reintegration Grantgave him the opportunity to come back to Europe and set uphis own research laboratory in his homeland.The traditional view of sexual selection involves males competingwith each other for access to females and females choosingthe best males. However, Dr Kuntner’s research is turning thisidea on its head. In the nephilid world, the confl ict is betweenmale and female, as the females want to mate with lots ofmales, while the males want to stop the females from matingwith other males.‘Classically, sexual selection is viewed as a female choice andfemales taken as the monogamous gender. Often, however, thisis entirely mistaken,’ explains Dr Kuntner. ‘In spiders, the femalesare highly polygamous, which is certainly not in the interest ofthe males which strive to monopolise the females, thus forcingmonogamy. Sexual confl ict over mating then triggers antagonismbetween the sexes.’Dr Kuntner’s research has revealed the lengths that malespiders will go to control access to females, as well as thetricks employed by females to get round the males’ ploys.Nephilid spider sex – out of all proportion!245