New Worlds: The case of the disappearing Hula frog

A black and green frog with orange and white splotches was the first amphibian to have officially been declared extinct.

By JUDY SIEGEL-ITZKOVICH
Frog 370 (photo credit: Hebrew University)
Frog 370
(photo credit: Hebrew University)
A black and green frog with orange and white splotches was the first amphibian to have officially been declared extinct by the International Union for Conservation of Nature (IUCN) in 1996; it was thought to have disappeared after Hula Lake dried up around 60 years ago. As a result, the opportunity to discover more about this species’ history, biology and ecology was thought to have disappeared.
But there is good news! The amphibian has been rediscovered and has turned out to be a unique “living fossil,” without close relatives among other living frogs.
Called the Hula painted frog, it was catalogued within the Discoglossus genus when it was first discovered in the Hula Valley in the early 1940s. A team of Israeli, German and French researchers now report in the journal Nature Communications on an in-depth scientific analysis of this mysterious amphibian.
The combined research effort that led to the revelation and analyses of the “extinct” frog was conducted by Rebecca Biton, a doctoral student of Dr. Rivka Rabinovich of the Hebrew University Institute of Archeology, and colleagues in Israel, France and Germany. Based on new genetic analyses of rediscovered individuals and the morphologic analyses of extant and fossil bones, the conclusion is that the Hula frog significantly differs from its other living relatives, the painted frogs of northern and western Africa.
Instead, the Hula frog is related to a genus of fossil frogs, Latonia, which were found over much of Europe dating back to prehistoric periods and has been considered extinct for about a million years.
The results imply that the Hula painted frog is not merely another rare species of frog but is actually the sole representative of an ancient clade of frogs (a group with a single common ancestor).
There are now plans to reflood parts of the Hula Valley and restore the original swamp habitat, which may allow for expansion in population size and a secure future for the rare amphibian.
OUTER-PLANET WEATHER GOES ONLY SO DEEP
If the nightly weather report at the end of the news were to give the temperatures and wind conditions on Uranus and Neptune, what would that involve? As these huge planets are home to extreme winds blowing at speeds of over 1,000 kilometers per hour, the prediction probably would be of huge, hurricane- like storms, immense weather systems that last for years and fastflowing jet streams. Both planets feature similar climates, despite the fact that Uranus is tipped on its side with the pole facing the sun during winter.
The winds on these planets have been observed on their outer surfaces – but to get a grasp of their weather systems, one needs to understand what is going on underneath.
For instance, do the atmospheric patterns arise from deep down in the planet or are they confined to shallower processes nearer the surface? New research at the Weizmann Institute of Science in Rehovot, the University of Arizona and Tel Aviv University, which was published recently in Nature, shows that the wind patterns seen on the surface can extend only so far down. Understanding the atmospheric circulation is not simple for a planet that lacks a solid surface, where Earth-style boundaries between solid, liquid and gas layers do not exist.
Uranus and Neptune are the farthest planets in the solar system, and there are still many open questions regarding their formation and composition. This study has implications for revealing the mysteries of their deep, dark interiors and may even provide information about how these planets were formed.
Since the discovery of these strong atmospheric winds in the 1980s by the Voyager 2 spacecraft, the vertical extent of these winds has been a major puzzle – one that influences our understanding of the physics governing the atmospheric dynamics and internal structure of these planets. But a team led by Dr.
Yohai Kaspi of Weizmann’s environmental sciences and energy research department realized they had a way, based on a novel method for analyzing the gravitational field of the planets, to determine an upper limit for the thickness of the atmospheric layer.
Deviations in the distribution of mass in planets cause measurable fluctuations in the gravitational field. On Earth, for example, an airplane flying near a large mountain feels the slightly elevated gravitational pull of that mountain. Like Earth, the giant planets of the solar system are rapidly rotating bodies.
Because of this rapid rotation, the winds swirl around regions of high and low pressure; in a non-rotating body, flow would be from high to low pressure. This enables researchers to deduce the relations between the distribution of pressure and density, and the planets’ wind field. These physical principles enabled Kaspi and his co-authors to calculate, for the first time, the gravity signature of the wind patterns and thus create a wind-induced gravity map of these planets.
By computing the gravitational fields of a large range of ideal planet models – ones with no wind – a task conducted by team member Ravit Helled of TAU – and comparing them with the observed gravitational fields, upper limits to the meteorological contribution to the gravitational fields were obtained. This enabled Kaspi’s team to show that the streams of gas observed in the atmosphere are limited to a “weather layer” of no more than about 1,000 km. in depth, which makes up only a fraction of a percent of the mass of these planets.
Although no spacecraft missions to Uranus and Neptune are planned for the near future, Kaspi anticipates that the team’s findings will be useful in the analysis of another set of atmospheric circulation patterns that will be closely observed soon: those of Jupiter. Kaspi, Helled and Prof. Bill Hubbard of the University of Arizona, who also contributed to this research, are part of the science team of NASA’s Juno spacecraft to Jupiter that was launched in 2011.
When it reaches Jupiter in 2016, it will provide very accurate measurements of the gravity field of this giant gaseous planet.