Environmental sex determination (ESD) 

is a process where the sex of an individual is determined by environmental factors, rather than genetic factors. In the case of frogs, the temperature of the environment during development is the primary determinant of sex. This means that frog embryos will develop as male or female based on the temperature of their environment during a critical period of development.

The exact temperature threshold for ESD varies between species, but it generally falls within a narrow range. For example, in the common frog (Rana temporaria), sex determination occurs between 16 and 22°C, with males developing at lower temperatures and females at higher temperatures. In some species, such as the green tree frog (Litoria caerulea), the range is even narrower, with temperatures between 25 and 28°C resulting in males and temperatures between 28 and 30°C resulting in females.

The importance of ESD in frogs is underscored by the fact that it can have significant ecological and evolutionary consequences. For example, in species where ESD is the primary mode of sex determination, shifts in temperature due to climate change can result in changes in the sex ratios of populations. This can have implications for population viability, as well as for the broader ecosystem.

There are also instances where the relationship between temperature and sex determination is more complex. For example, in some species, exposure to certain chemicals or pollutants can disrupt ESD and lead to changes in sex ratios. In other cases, genetic factors may interact with temperature to determine sex, leading to more nuanced patterns of sex determination.

Overall, the phenomenon of ESD in frogs highlights the remarkable ability of these animals to adapt to their environment. While ESD can have ecological and evolutionary consequences, it also represents an important area of study for researchers interested in understanding the mechanisms that underlie sex determination and developmental plasticity.

What does Environmental Sex Determination (ESD) in frogs have to do with me?

References and more material if you are interested in this subject:

Janzen, F. J., & Phillips, P. C. (2006). Exploring the evolution of environmental sex determination, especially in reptiles. Journal of Evolutionary Biology, 19(6), 1775-1784. 

Pieau, C., & Dorizzi, M. (2004). Oestrogens and temperature-dependent sex determination in reptiles: all is in the gonads. Journal of Endocrinology, 181(3), 367-377.

Rollins-Smith, L. A. (2009). The role of amphibian antimicrobial peptides in protection against pathogens and their potential as therapeutic agents. Peptides, 30(11), 2071-2078.