Interesting Science This Week. Week 7

Originally posted on January 06, 2017 at my blogger site.

In our modern liberal society, a great deal of effort has gone into eliminating the differences in how women are treated from men. In nature, however, male and female sexes have well defined roles in ensuring that perpetuation and evolution of life is not interrupted. Recently published research has indicated that the distinct biological roles of the two sexes also contributes to determining the lethality of infections by bacteria and viruses. It was well known that many bacterial and viral infections tend to be deadlier in men than in women. Men who are infected by TB causing bacteria, for example, are 1.5 times more likely to die due to infection than women. Similarly, many cancers are more likely to lead to death in men than in women. This difference in susceptibility to pathogenic infections among men and women was hypothesized to be due to the different sex hormones. However, in a recent paper published in the journal Nature Communications, researchers from Royal Holloway University of London have reported the results of their work that shows that the observed difference in lethality of bacterial or viral infections could be because it might be evolutionarily advantageous for the pathogen to keep the infected women alive. This, the researchers argue, is because women can transmit the pathogen to a wider population of hosts through pregnancy and nursing. To support their hypothesis, the scientists have examined the case of Human T-cell Lymphotorpic Virus Type-1 (HTLV-1) that causes Adult T-cell Leukemia (ATL), a type of blood cancer and is highly prevalent among Japanese and Caribbean populations. While the infection by HTLV-1 virus is equally lethal in both men and women in the Caribbean population, it is more lethal among Japanese men than women. The scientists have explained that this difference is because the Japanese women breastfeed for longer duration than Caribbean women. This incentivizes the virus to evolve such that they are less virulent in the body of Japanese women since that will help them survive longer. How the pathogen identifies the sex of its host is an interesting puzzle that needs to be unravelled through further research.

Bats are probably one of the most vilified animals in our popular culture, along with Owls. Every horror or thriller movie has atleast one scene starring these flying mammals. Usually these scenes feature a large number of bats rushing out of a cave or some such desolate space accompanied by a lot of noise just as one of the characters is trying to enter. A group of researchers from Israel have now come out with a study where they have tried to understand if there is any meaning and purpose to these sounds that the bats make.  The results of this study have recently been published in the journal Scientific reports. To conduct this study, the scientists collected a group of Egyptian fruit bats in a room and continuously recorded their sounds and actions for 75 days. They then used a computer program to analyze thousands of sounds and correlated them to actions from the video recordings. From these analyses, the researchers identified that most of the sounds that the bats made were not random but had a specific context in the everyday life of the animals. Not only did these sounds have a purpose, they were also directed at a specific member of the group. The bat sounds also had different intonations depending on the sex of the recipient of the sound. Most interestingly, the scientists discovered that more than 70% of the sounds that they analyzed could be attributed to just 4 different behavioural contexts – quarelling over food, bickering about the sleeping spot, raising alarm when another member of the group came too close to a bat  and a female protesting against the attempts of a male bat to have sex. Apart from contributing to the understanding of the social behaviour of the bats, this work has the potential of forming the foundation to explore the vocal communication among other animals.

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