They are mum’s first gift to her newborn baby on the day of its zeroeth birthday – bacteria, fresh from her vagina. Vaginal bacteria are among the trillions of microscopic hitchhikers that share our bodies with us. Collectively known as the ‘microbiota’, these passengers outnumber our own cells by ten to one. Children partly inherit their microbiota from their mothers. During birth, they pass from the largely bacteria-free conditions of the womb through the microbe-laden vagina into the equally bacterial outside world.
Being slathered in vaginal microbes might not seem like much of a treat from our adult perspective, but to a newborn, it’s a key event. The microbiota are important partners, influencing our physiology and our risk of disease. Now, Maria Dominguez-Bello from the University of Puerto Rico found that the way we enter the world determines the identities of our first bacterial colonisers. Babies delivered by Caesarean section end up with a very different portfolio to those who are born naturally.
Normally, the duck keeps its penis inside-out within a sac in its body. When the time for mating arrives, the penis explodes outwards to a fully-erect 20cm, around a quarter of the animal’s total body length. The whole process takes just a third of a second and Brennan captures it all on high-speed camera. This isn’t just bizarre voyeurism. Duck penises are a wonderful example of the strange things that happen when sexual conflict shapes the evolution of animal bodies.
Childhood… violated… Innocence… lost… SCIENCE!Many ducks form bonds between males and females that last for a whole mating season. But rival males often violently force themselves onto females. To gain the edge in these conflicts, drakes have evolved large corkscrew phalluses, lined with ridges and backward-pointing spines, which allow them to deposit their sperm further into a female than their rivals. These extreme penises are even more unusual when you consider that 97% of bird species lack any penises whatsoever.
But female ducks have developed countermeasures. Their vaginas are equally long and twisting, lined with dead-end pockets and spirals that curve in the opposite direction. They are organic chastity belts, evolved to limit the effectiveness of the males’ lengthy genitals. Two years ago, Brennan showed that duck species whose males have the longest penises tend to have females with the most elaborate vaginas. Now, she has found further evidence that these complex genitals are the result of a long-lasting war of the sexes.