Geckos using narrow tree perches have longer limbs than expected
Some lizards, notably anoles, that use narrow perches in trees have evolved shorter limbs. This correlation is likely due to biomechanical trade-offs between sprint speed, balance and limb length, suggesting that relatively short limbs may be a common adaptation to movement on narrow perches. A new PLOS ONE study tested the relationship between limb length and perch size in Australian geckos, many of which also use adhesive toe pads to climb trees, yet are only distantly related to anole lizards.
Surprisingly, the authors found that geckos which used narrower tree perches tended to have longer limbs than those using wide perches: the opposite relationship to that seen in anoles. The authors speculate that geckos may not be subject to same trade-off between speed and balance as anoles, and so may negotiate narrow perches differently. They see this as an example of how even when species use similar habitats, their separate evolutionary histories can still give them individual characteristics.
Research Article: Hagey TJ, Harte S, Vickers M, Harmon LJ, Schwarzkopf L (2017) There’s more than one way to climb a tree: Limb length and microhabitat use in lizards with toe pads. PLoS ONE 12(9): e0184641. https://doi.org/10.1371/journal.pone.0184641
Image Credit: Hagey et al (2017)
Male hormones may promote infection by Kaposi’s Sarcoma Virus
Men appear to be especially vulnerable to infection with a virus which can cause Kaposi’s sarcoma, a type of cancer, suggesting that male hormones might influence infection. A PLOS Pathogens study has now elicited a possible mechanism for this effect. The study authors used human cell cultures to examine the androgen receptor and the hormone, DHT, which binds it. While the receptor is present in some cell membranes in both men and women, the hormone is found at much higher levels in men.
Using RNA interference techniques to inhibit androgen receptor activity, the researchers found that binding of the androgen receptor usually triggers a molecular signaling pathway that permits the virus to enter cells, promoting infection. These results could therefore help explain why men have an increased risk of viral infection and so of developing Kaposi’s sarcoma, and could guide future drug development.
Research Article: Wang X, Zou Z, Deng Z, Liang D, Zhou X, Sun R, et al. (2017) Male hormones activate EphA2 to facilitate Kaposi’s sarcoma-associated herpesvirus infection: Implications for gender disparity in Kaposi’s sarcoma. PLoS Pathog 13(9): e1006580. https://doi.org/10.1371/journal.ppat.1006580