Red-eyed treefrogs, Agalychnis callidryas, lay jelly-covered egg clutches on leaves overhanging tropical ponds. Each clutch of several dozen transparent eggs is ready to hatch after only four days.
By delaying hatching by a few more days, frog embryos significantly increase their chances of survival as tadpoles in the pond below where predators lurk. But as each egg matures, and embryos need more oxygen, less and less of the vital substance is available inside.
Warkentin has measured oxygen levels as low as 2% air saturated in the middle of red-eyed treefrog eggs—yet the embryos refrain from hatching. "You'd think they would be dead. You'd think they would hatch. But they continue to develop at the same rate as embryos in eggs with much, much more oxygen," she explains. "Jessica found that these embryos maintain high metabolic rates and rapid, synchronous development by behaviorally positioning their external gills in a small high-oxygen area, a sweet spot near the exposed surface."
The team used a video camera to record embryo movement in the egg. By gently manipulating the eggs with a probe, Rogge turned the embryos within the eggs so that the gills were positioned away from the surface, in lower oxygen. "It's a lot like trying to pick something up out of a glass of water with your fingers," says Rogge, "the embryo 'wants' to be at the front of the egg, so unless I turned the embryo completely around in one motion it would come back to the front before I could finish spinning it."
Rogge found that even very young, neural-tube-stage embryos, before developing gills, blood, or the ability for muscular movement, kept their developing head in the oxygen sweet spot. "Once we started with the behavior research, it sort of snowballed and we suddenly got to the point where I spun the one-day-old embryos. We figured they would turn back, because they had ciliary rotation, but watching them ever so slowly return to the front, almost like clock-work, was amazing."
Rogge also induced embryos to lose their gills in the egg -- and was thus able to directly measure and compare the oxygen uptake ability of animals with and without gills, in eggs and in the water. "Embryos normally keep their external gills as long as they stay in the egg, but when they hatch they re-route the blood flow and the gills shrivel up in a matter of minutes" said Warkentin. "Now this makes sense. The external gills aren't much use to tadpoles, but they seem to be critical for embryos if they are to get enough oxygen."
People don't typically think of eggs as "doing" much. However, early development is a crucial time when death is a common occurance, and natural selection will favor any ability the embryo may have that increases its chances of survival.
Beth King | EurekAlert!
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22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden
The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
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