Did you know that electric fishes evolved independently two times: one lineage in Africa and one in South America? I didn’t know that either until I went to the great talk from Harold Zakon which he gave yesterday in the Bernstein Centre for theoretical Neuorsciences Berlin. Interestingly both lineages have fishes which communicate via electric waves and fishes which use electric pulses instead. What is the molecular basis for that difference in electronic mechanism? Which channel mutation lead from continuous waves to short pulses? For the African lineage, Zakon and his coworkers were able to show that the transition from electric wave to electric pulse was based on a mutation in the voltage gated potassium channel. The insertion of negative Aminoacids in the top of the channel (S3-S4 linker) leads to an increased voltage sensitivity (faster and earlier opening of the ion channel) which results in a shortening of the electric signal (the action potential). What I liked a lot, is the fact that such a sort of mutation (change the polarity of the ion channel to make it more voltage sensitive) is also found in other species. Zakon told us that for example in sharks there is a mutation of positive Aminoacids in the bottom of a Calcium channel which also leads to an increased voltage sensitivity and shapes the electro-sensation of sharks. See for example:
"Regulation and modulation of electric waveforms in gymnotiform electric fish." Stoddard, Philip K., et al. Journal of Comparative Physiology A 192.6 (2006): 613-624.
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Appel and Cocroft (2014) published a paper in which title they claimed that “plants respond to leaf vibrations caused by insect herbivore chewing”. In their study, the plant defence mechanism (production of toxins) which is normally activated by the feeding caterpillars, could also be activated by appropriate application of acoustic vibration directly to a leaf. That means that the acoustic vibrations are either directly transmitted through the leaf tissue or (even more interesting) are transmitted through the air and detected by plant “ears” (antenneas). If the latter is true, plants could “hear” if a neighbour plant is attacked, just by detecting the chewing sound waves of the caterpillars. Is that possible? “Yes it is possible” says the paper from Shaobao Liu et al. (2017). They analyzed if the Arabidopsis trichomes (hair cells) which has several mechanosensory functions, could additionally work as acoustic detectors. For that they analyzed geometry, mass and stiffness of the trichomes and showed theoretically that their primary modal frequencies would be able to resonate when exposed to acoustic waves with the frequencies similar to chewing caterpillar. In easy words: theoretically the trichomes could work like ears for the plant and detect chewing sounds. "Arabidopsis Leaf Trichomes as Acoustic Antennae."
Liu, Shaobao, et al. Biophysical Journal 113.9 (2017): 2068-2076. Alabaster is great for building statues, artworks and monuments. That is a fact which did not change since medieval times. The question is, where the medieval and Renaissance sculptors in Europe got their alabaster from? W. Kloppmann et al. (2017) show that isotope fingerprints of the alabaster can link artworks to their source areas. The method benefits i.a. “from the strong variations of isotope ratios of S, O, Sr in seawater and the associated evaporites through the Mesozoic”. That means that, although optically there is no difference between different alabster peices, every alabaster quarry (“mine”) differs in its mixture of S, O and Sr isotopes. In order to test this new method for finding the origin of alabaster, W. Kloppmann et al. analyzed 66 alabster artworks from different museums and collections. They were able to show that besides the known alabaster quarries in the English Midlands and in northern Spain, there was also a long-lived but little-documented alabaster trade radiating from the French Alps. |
IdeaI love to increase my general science knowledge by reading papers from different fields of science. Here I share some of them. Archiv
März 2018
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