ok, ok — so maybe they’re not really people, but they are pretty d*rn cool! no really!
bet ya didn’t know (or maybe you do) that they can tell if you’re wearing a red or a blue shirt. or that they know when the fruit of neighboring plants is ripe. or that they have short-term memory.
yes, short-term memory:
“As we saw back in chapter three, the Venus flytrap needs to know when an ideal meal is crawling across its leaves. Closing its trap requires a huge expense of energy, and reopening the trap can take several hours, so Dionaea only wants to spring closed when it’s sure that the dawdling insect visiting its surface is large enough to be worth its time. The large black hairs on their lobes allow the Venus flytraps to literally feel their prey, and they act as triggers that spring the trap closed when the proper prey makes its way across the trap. If the insect touches just one hair, the trap will not spring shut; but a large enough bug will likely touch two hairs within about twenty seconds, and that signal springs the Venus flytrap into action.
“We can look at this system as analogous to short-term memory. First, the flytrap encodes the information (forms the memory) that something (it doesn’t know what) has touched one of its hairs. Then it stores this information for a number of seconds (retains the memory) and finally retrieves this information (recalls the memory) once a second hair is touched. If a small ant takes a while to get from one hair to the next, the trap will have forgotten the first touch by the time the ant brushes up against the next hair. In other words, it loses the storage of the information, doesn’t close, and the ant happily meanders on. How does the plant encode and store the information from the unassuming bug’s encounter with the first hair? How does it remember the first touch in order to react upon the second…?
“In their [Dieter Hodick and Andreas Sievers] studies, they discovered that touching a trigger hair on the Venus flytrap causes an electric action potential that induces calcium channels to open in the trap (this coupling of action potentials and the opening of calcium channels is similar to the processes that occur during communication between human neurons), thus causing a rapid increase in the concentration of calcium ions.
“They proposed that the trap requires a relatively high concentration of calcium in order to close and that a single action potential from just one trigger hair being touched does not reach this level. Therefore, a second hair needs to be stimulated to push the calcium concentration over this threshold and spring the trap. The encoding of the information is in the initial rise in calcium levels. The retention of the information requires maintaining a high enough level of calcium so that a second increase (triggered by touching the second hair) pushes the total concentration of calcium over the threshold. As the calcium ion concentrations dissipate over time, if the second touch and potential don’t happen quickly, the final concentration after the second trigger won’t be high enough to close the trap, and the memory is lost….
“Here, then, lies the proposed mechanism of the short-term memory in the Venus flytrap. The first touch of a hair activates an electric potential that radiates from cell to cell. This electric charge is stored as an increase in ion concentrations for a short time until it dissipates within about twenty seconds. But if a second action potential reaches the midrib within this time, the cumulative charge and ion concentrations pass the threshold and the trap closes. If too much time elapses between action potentials, then the plant forgets the first one, and the trap stays open.
“This electric signal in the Venus flytrap (and the electric signals in other plants for that matter) are similar to the electric signals in neurons in humans and indeed all animals. The signal in both neurons and Dionaea leaves can be inhibited by drugs that block the ion channels which open in the membranes as the electric signal passes through the cell. When Volkov pretreated his plants with a chemical that inhibits potassium channels in human neurons, for example, the traps didn’t close when they were touched or when they received the electric charges.”
that’s from What a Plant Knows? A Field Guide to the Senses. if you’re looking for an easy but info-packed read to bring with you on your summer vacation, you could do a lot worse. i’m reading it right now (well, not right now) and it’s terrific! the book is by the author of The Daily Plant (heh) blog.
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don’t miss jayman’s thorough summary of what we’ve been discussing around here over the past year or so (thanks, jayman!!). he’s also thrown in a couple of new ideas of his own that are real zingers, so check it out!:
just when you think you’ve got inbreeding and genetics sorted out in your head (almost — well, no, not really), they throw something new at ya.
here’s an article that linton @nobabies.net pointed out to me (thanks, linton!):
“Epigenetics Linked to Inbreeding Depression”
16 September 2011
“Inbreeding depression is the bane of conservation biology. When closely related individuals mate, which can happen when there aren’t too many members of a species left, their offspring are often less fit and less fertile, making the species all the more vulnerable. Both plants and animals can suffer from inbreeding depression, and textbooks typically attribute this phenonmenon to genetics: Recessive genes with harmful effects, whose negative influences are normally masked by a dominant copy of a gene, are more likely to pair up in offspring of more genetically similar parents.
“Or so the theory goes.
“But Philippine Vergeer, an evolutionary ecologist at Radboud University Nijmegen in the Netherlands, suspects that epigenetics — chemical modifications to the DNA that alter gene activity — may also be to blame, at least in plants….
“Vergeer and her Radboud colleagues Niels Wagemaker and Joop Ouborg compared DNA methylation between outbred and inbred S. columbaria — also known as small scabious — derived from the same mother plant. Methylation was 10% higher in inbred plants…. Also, inbred and outbred plants have different parts of their genomes methylated.
“The scientists then decided to look at what happened to plant offspring if they reconfigured the flora’s methylation. Every day for a week, they exposed germinating seeds of inbred and outbred plants to a demethylating agent. The result: ‘Phenotypic differences between outbred and inbred plants are nullified,’ Vergeer reported….”
so, at least in the case of these little plants, inbreeding depression seems to be connected to epigenetics and not genetics. when they reversed the epigenetics in these plants, the inbred plants photosynthesized (which is what the researchers were measuring) just as well as the outbred plants.
there has been some research done showing that epigenetic states are probably regulated (if that’s the right way to put it) by the underlying genetics, so perhaps the inbreeding depression in these plants was still a result of too many “bad genes.” but it’s cool that they could reverse the inbreeding depression by getting rid of the methylation!
there have also been studies, of course, showing that some epigentic states can be inherited across a few or several generations.
previously: the genetics of epigenetics
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biology is so cool:
“[F]or any woman that has ever been pregnant, some of her baby’s cells may circulate in her bloodstream for as long as she lives. Those cells often take residence in her lungs, spinal cord, skin, thyroid gland, liver, intestine, cervix, gallbladder, spleen, lymph nodes, and blood vessels. And, yes, the baby’s cells can also live a lifetime in her heart and mind.
“Here’s what happens.
“During pregnancy, cells sneak across the placenta in both directions. The fetus’s cells enter his mother, and the mother’s cells enter the fetus. A baby’s cells are detectable in his mother’s bloodstream as early as four weeks after conception, and a mother’s cells are detectable in her fetus by week 13. In the first trimester, one out of every fifty thousand cells in her body are from her baby-to-be (this is how some noninvasive prenatal tests check for genetic disorders). In the second and third trimesters, the count is up to one out of every thousand maternal cells. At the end of the pregnancy, up to 6 percent of the DNA in a pregnant woman’s blood plasma comes from the fetus. After birth, the mother’s fetal cell count plummets, but some stick around for the long haul. Those lingerers create their own lineages. Imagine colonies in the motherland….
“How many people have left their DNA in us? Any baby we’ve ever conceived, even ones we’ve miscarried unknowingly. Sons leave their Y chromosome genes in their mothers. The fetal cells from each pregnancy, flowing in a mother’s bloodstream, can be passed on to her successive kids. If we have an older sibling, that older sibling’s cells may be in us. The baby in a large family may harbor the genes of many brothers and sisters. My mother’s cells are in my body, and so are my daughter’s cells, and half my daughter’s DNA comes from her dad. Some of those cells may be in my brain….”
wikipedia says (so it must be true): “After giving birth, about 50-75 % of women carry fetal immune cell lines. Maternal immune cells are also found in the offspring yielding in maternal→fetal microchimerism, though this phenomenon is about half as frequent as the former”
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world’s biggest bug — all 71 grams (2.5 ounces) of
him, pardon me, her(!) — luuuuvs carrots (and small babies, presumably). he’s she’s so cute! (^_^)
see also: Meet the world’s heaviest insect, which weighs three times more than a mouse… and eats carrots in the daily mail — and Dr. Bugs, website of mark moffett, the guy who found this giant weta in new zealand.
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