Spread your sperm the smart way
Attractive males release fewer sperm per mating to maximise their chances of producing offspring across a range of females, according to a new paper on the evolution of ejaculation strategies. The findings by researchers at UCL (University College London) and the University of Oxford suggest that, paradoxically, matings with attractive males may be less fertile than those with unattractive ones.
In a paper to be published in the journal American Naturalist, the team mathematically modelled a range of male ejaculation strategies to look for the optimum “sperm load” per mating, and how this might vary depending on mating patterns. Previous studies have shown that in animals such as the domestic fowl, and fish such as the Arctic charr, males with privileged access to females produce ejaculates of lower fertilising quality than subordinate males.
Sam Tazzyman, UCL CoMPLEX (Centre for Mathematics and Physics in the Life Sciences and Experimental Biology), says: “In some species, females mate with many different males. Each male’s sperm competes with that of other males in a process known as ‘sperm competition’. Since males have finite resources to allocate to breeding, they allocate them carefully to each mating to maximise their number of offspring. If a male puts a lot of resources into each mating he will get more offspring per mating, but at the expense of fewer matings. If, on the other hand, a male puts few resources into each mating he will secure less paternity per mating, but will be able to carry out more matings overall. Thus, there is a trade-off between number of matings and success per mating.”
Teens’ drinking linked to mental health problems
Teenagers who drink heavily are also more likely than their peers to have behavioral problems or symptoms of depression and anxiety, a new study finds.
The study, of nearly 9,000 Norwegian teenagers, found that those who said they had been drunk more than 10 times in their lives were more likely to have attention and conduct problems in school. Meanwhile, heavy-drinking girls showed higher rates of depression and anxiety symptoms.
The findings, published in the online journal Child and Adolescent Psychiatry and Mental Health, are based on a one-time survey. They do not, therefore, show whether the drinking came before or after the teenagers’ other problems.
Pigs at risk from people as new flu spreads
There is a growing risk that pigs will catch the new H1N1 flu strain—commonly known as swine flu—from humans, German researchers said on Thursday.
Widespread transmission from people to pigs could mix up virus strains further, leading to unpredictable changes in the disease.
There have already been a handful of suspected cases of humans passing the current pandemic H1N1 virus to swine. The latest German research confirms it is infectious to pigs and can spread rapidly.
Number of US preterm, low birth weight babies down
The encouraging news: After several decades of steady increases, the percentages of infants born preterm and the percentage born with low birth weight declined slightly in 2007 in the US, according to a report released today.
The bad news: In 2007, 18% of all US children ages 0 to 17 lived in poverty, up from 17% the year before, Dr. Duane Alexander, Director of Eunice Kennedy Shriver National Institute of Child Health and Human Development, noted at a telebriefing describing highlights of the US government’s annual report on the well-being of American children.
“Infants born preterm and of low birth weight are at increased risk for infant death and they also have a greater chance of lifelong disabilities such as blindness, deafness and cerebral palsy, making this an extremely important indicator of child well-being,” Alexander noted.
Mom’s drug use tied to child-abuse risk
Young children whose mothers abuse drugs may face a higher risk of abuse and placement in foster care, a new study finds.
Australian researchers found that infants whose mothers abused amphetamines or opiates such as heroin were 13 times more likely to become victims of neglect or abuse than other children their age. Their odds of being placed in foster care were similarly elevated, according to findings published in the journal Pediatrics.
Using data from child-protection services, Andrea McGlade of the Royal Children’s Hospital in Brisbane and her colleagues found that half of the children born to drug-abusing mothers became victims of neglect or physical, emotional or sexual abuse.
