Non-recombining sex chromosomes, such as the Y chromosome, are expected to degenerate over evolutionary times because they accumulate deleterious mutations that cannot be corrected by recombination with a pristine copy. In most cold-blooded vertebrates, such as frogs, however, sex chromosomes are undifferentiated. Why is that so? On the one hand, the “high-turnover” hypothesis holds that these sex chromosomes are regularly replaced before they had time to decay. On the other hand, the “fountain-of-youth” hypothesis posits that they are regularly rejuvenated by X-Y recombination in sex-reversed XY females. Here, we show that three species of tree frogs that diverged more than 5.4 million years ago share the same pair of undifferentiated sex chromosomes. Although male recombination stopped before species divergence, X and Y alleles show no differentiation, and cluster by species, not gametologs. We conclude that their sex chromosome homomorphy is not due to a recent turnover but is maintained over long evolutionary times by occasional recombination. Such rare episodes of X-Y recombination are expected to have long-lasting consequences on the evolution of sex chromosomes and sex antagonistic genes. Leer más.

Los Agentes Forestales de la Comunidad de Madrid han llevado a cabo junto con voluntarios y personal del Centro de Educación Ambiental de Chapinería un operativo de rescate de aproximadamente 3000 anfibios, que estaban atrapados en la piscina municipal de Valdemorillo. La mayoría eran ejemplares de gallipato (Pleurodeles waltl) y sapo de espuelas (Pelobates cultripes). Leer más.

Los últimos cuatro kilómetros de subida a la Peña de Francia serán adaptados para la preservación de la Lagartija de Las Batuecas, una especie muy amenazada y en peligro de extinción, que sólo se puede contemplar en esta formación montañosa y que, además, es el único vertebrado endémico de Castilla y León. Leer más.

A popular «get well» card shows a racoon saying to a snake, «You wouldn’t get these stomach aches if you chewed your food properly.» Vets know, however, that indigestion in snakes and other reptiles often results not from swallowing food whole but from a parasitic infection. The gastrointestinal disease cryptosporidiosis represents a particularly severe problem: although it is rarely otherwise serious in mammals, reptiles seem especially prone to it and the condition is often fatal. Furthermore it is highly contagious, so early diagnosis would represent a good way to limit its spread among reptiles. Unfortunately, though, diagnosis is extremely difficult. Leer más.

Get your virtual scalpels ready! Frog dissection has long been a mainstay of high school biology classes, but slicing into real amphibians could become a thing of the past. A new push by animal rights activists called «Race to Stop Dissections» hopes to get schools to adopt anatomy software that lets students dissect digital frogs instead. Leer más.