Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Better Smaller, But More

15.04.2002


In the city, frogs do not feel as comfortable as in the wild nature because of dirty water, a lack of food, and dangers at every turn. That is why the life of frogs in urban areas is shorter. However, they do not leave these habitats, but adapt to them. Apparently, there are two ways to adapt: either become more tolerant or increase the number of progeny.



Every spring from 1998 to 2001, Elena A. Severtseva and her colleagues from the Biological Faculty of the Moscow State University studied the spawn of two frog species (Rana temporaria and Rana arvalis) most common in Moscow parks and ponds. The scientists counted the number of layings and the quantity of eggs in each laying and measured the diameter of eggs and their yolks using a microscope.

In average, Moscow frogs have smaller eggs than their sisters in the countryside, but each urban frog lays several hundred eggs more than the rural one. The egg diameter is about one millimetre, and the difference between egg sizes in the city and suburbs constitutes several decimal fractions of millimetre, but that is sufficient to gain in quantity. At the same time, urban conditions do not change the yolk size in relation to that of the whole egg; sometimes yolks of Moscow frogs are even larger. Therefore, the embryo has a sufficient food supply to grow into the tadpole, though tadpoles from small eggs need a longer time for development.


The amphibians were studied in several places within Moscow: near the Gorodnya River, in the vicinity of the Kapotnya Oil Plant (district Brateevo), in Vostryakovo (in a pond adjacent to the Moscow Ring Highway and in other three ponds in the park near the cemetery), in the area of Matweevskoe (the Setun River floodplain), and near the railway station Ramenskoe. Similar observations were done at the biological stationary near town Zvenigorod.

Both frog species spend most of their life on the land and come into water pools only to spawn. City frogs are very reticent and almost silent at the breeding time. The researchers have heard their sounds only in Matveevskoe. While the spawn of suburb frogs is assembled in large clusters, that of Moscow ones appears in small clusters all over the spawning area. Oil products and chemicals dissolved in water kill many embryos. The rate of embryo death in Brateevo is five times as high as in natural conditions and reaches 12%. Hence, to survive in cities, the high quantity of eggs is more important than a large size of embryos, the scientists conclude.

Alexander Barne | alphagalileo

More articles from Life Sciences:

nachricht Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care

nachricht Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>