ABOVE: A male funnel-web spider (left) waves his legs in a mating dance for the female (right).

Funnel-web spiders (Agelenopsis pennsylvanica) engage in an eye-catching mating ritual, complete with drumming and dance, and alter their behavior depending on what microbes are present on their sexual organs, researchers reported July 29 in Ethology

Male funnel-web spiders sway their abdomens, wave their legs, and pound on their webs to attract female attention. If a female responds to his courtship, the male delivers his sperm into her reproductive organs with appendages called pedipalps and then quickly retreats, as females sometimes devour their mates. 

Both the males’ pedipalps and females’ abdomens carry distinct strains of bacteria, the scientists found. The researchers wanted to see “what happens when you modify the bacterial load on these spiders in the context of a super important behavior, which...

The team coated the pedipalps of 20 males and abdomens of 10 females with a custom cocktail of bacteria. Unaltered males took about 4.6 times longer to start courting bacteria-coated females, beginning their dance after spending about about 10 minutes near the female, instead of about two minutes. However, males moved faster if the bacteria-coated female behaved aggressively, perhaps because the threat of attack outweighed the risk of infection, the authors suggest. 

About half of the unaltered females who mated with bacteria-coated males died after 40 days, but all the bacteria-coated females survived, suggesting the former group may have died of sexually transmitted infections.  

Here, the female funnel-web spider (below) is in catalepsis, which is a trance-like quiescent state brought on by exposure to male pheromones.

M.E. Spicer et al., “Spiders, microbes and sex: Bacterial exposure on copulatory organs alters mating behaviour in funnel-web spiders,” doi:10.1111/eth.12921, Ethology, 2019.

Nicoletta Lanese is an intern at The Scientist. Email her at nlanese@the-scientist.com.

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