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.
Alexander Barne | alphagalileo
New application for acoustics helps estimate marine life populations
16.01.2018 | University of California - San Diego
Unexpected environmental source of methane discovered
16.01.2018 | University of Washington Health Sciences/UW Medicine
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
16.01.2018 | Materials Sciences
16.01.2018 | Materials Sciences
16.01.2018 | Power and Electrical Engineering