Science news

From New Scientist

Beetles develop "weaponry" through female competition


Female dung beetles have developed larger horns, compared to their male counterparts, due to competition with other females for resources to feed their larval young.

According to Patricia Blackwell, a behavioral ecologist at the Australian National University in Canberra, this is rare.

Females of other species -- like lizards and crabs -- developed "weaponry" to defend against predators.

In a study at the University of Western Australia, Perth, researchers Nicola Watson and Leigh Simmons pitted female beetles against each other in a race for dung. Matched for body size, females with the largest horns managed to collect more dung and better provide for their offspring.

"Dung loses its usability quickly, so they have to seize it fast," says Watson. Females beetles have been found to steal dung and raid other "stashes." The larger horns evolved as a result of this intense female-female rivalry.

Better genes, more sex partners?

Genes related to the immune system may explain why some women have have more sex partners, an Australian study suggests.

The major histocompatibility complex(MHC)is a region of DNA vital to the immune system. The more diverse the genes of MHC, the more effective it is at conferring disease resistance and, in a variety of animals, individuals with diverse MHCs are likely to be chosen as a sexual partner.

Although further research in humans is needed, Hanne Lie of the University of Western Australia,Perth measured the diversity of the MHC in 74 heterosexual female students and asked them about the number of sexual partners they had. After controlling for attitudes towards sex, and age of first intercourse, she found that the greater a woman's MHC diversity, the more sexual partners she had.

However, whether women with diverse MHCs have greater evolutionary success is debatable. One factor could be contraception.

Boguslaw Pawlowski, an anthropologist at the University of Wroclaw in Poland says use of contraception means there may not be a strong correlation between the number of sexual partners and reproductive success.

Fetuses react to transient emotions

While stress or depression during pregnancy can harm a fetus, less is known about fleeting emotions, like happiness or sadness.

During a study at Nagasaki University in Japan, 10 pregnant women were shown a cheery five-minute clip from the movie, "The Sound of Music" while 14 other women watched a tear-jerking five minutes from "The Champ." Each clip was sandwiched between two "neutral" samples so that the researchers could measure changes in fetal movements against a baseline.

Women listened to the films through headphones to ensure that only the effects of their emotions, and not sounds, were being measured. Fetuses can hear by the last trimester.

Researchers counted the number of arm, leg, and whole body movements via ultrasound and found that the fetuses moved their arms significantly more during the "happy" film clips than during a "neutral" clip, and less during the "sad" film clip.

While more research is needed, the results suggest that sadness releases more of the "fight or flight" hormone, which redirects blood away from the uterus.