Migmatites and Ptygmatic Folding

         Let's examine ptygmatic folding in migmatites (huh?). Take a look first:








                                                         Migmatites are a mixture of metamorphic and igneous rock. The pink plagioclase feldspar in the rock below formed a ptygmatic fold after remelting of the lighter colored minerals:

         
           Thus, this remelting creates a mixture of the unmelted metamorphic part with the recrystallized igneous part. Migmatites tend to occur at very high-pressure and high-temperature zones and in very old rocks (such as Precambrian).

           The word ptygmatic was introduced into the geological literature by Jakob J. Sederholm in 1907 and originates from the ancient Greek word for “fold” or “anything folded.” The term “ptygmatic fold” is somewhat redundant, like saying “a folded fold.” However, the term “ptygmatic” in the geologic literature generally refers to tight folds that form when the folded material has a greater viscosity than the surrounding medium. In migmatites, ptygmatic folds generally form in the more viscous lighter layers.   

      A look at Bowen's Reaction Series:

              

          shows why the darker minerals such as olivine, pyroxene, amphibole, and biotite tend not to remelt as it takes higher temperatures for this to happen. The lighter-colored K-spar, muscovite and quartz melt at much lower temperatures forming those ptygmatic folds of newly igneous material.

      Sometimes, differentiating between migmatites and metamorphic gneisses can be difficult--but we'll leave that for a later, gneisser time.

Migmatitely,

Steph

Gerenuk: the Giraffe-Necked Gazelle With A Stone Skull

           The gerenuk is a long-necked gazelle, also known as the Waller's gazelle, that lives in eastern Africa:

           I've been perusing lists of wild mammals who are not native to North America for the NPR Sunday Puzzle and discovered this beautiful beast with wonderful coloring

and a sweet face:

          The word gerenuk is from the Somalian word garanug meaning a long-necked or giraffe-necked gazelle. The genus and species name Litocranius walleri
is from lithos, Greek for stone (so, of course, I was even more curious) and kranion, Greek for the upper part of the skull. The "stone skull" is a reference to the skull which is almost solid bone at the base of the horns.

       The Waller's gazelle is named for the Reverend H. Waller (1833-1901), a friend of the infamous Dr. Livingstone (I presume).

           Reverend Waller spent much time in this part of Africa with the gerenuks:

          The gerenuk feast on leaves, fruits, and plants, especially those higher up in the desert brush. They like to browse together in groups but have little need for a water cooler to gather about as gerenuks almost never drink water, getting most of their water from the food they eat.

          In ancient African tribal tales, the gerenuk has been crowned "Queen of Humbleness" due to their looking out for one another. . .and never needing an "Attaboy or attagirl." ;-)

Seen any gerenuks (or other interesting mammals) lately?

Steph

Going Batty: Lack of Rest Tied to Fungal White-Nose Syndrome

        The bats won out as the topic for this week's PEOTS (although, sadly, the bat populations are losing millions to the fungal White Nose Syndrome since 2006). Look at these incredible images from today's New York Times: 

         

           Continuing last week's examination of an animal with low cancer rates, the Bowhead Whale, this week's look at bats shows a mammal with almost non-existent tumours.  Bats are also carriers of many viruses from Ebola to mumps and measles without showing symptoms of the diseases they carry.

           From the New York Times article:

          "Scientists traditionally have divided bats into two big suborders: the fruit-eating megabats and insect-eating microbats, deeming the groups so distinct they might have evolved flight independently."

           "Yet recent genomic analysis in the journal Science reveals that the ability to fly dates to the earliest days of the bat lineage, some 90 million years ago, and that megas did not split from micros for another 10 million years, after which the micros alone evolved the capacity for echolocation, to help them hunt their insect prey." [These are Wrinkle-lipped bats in Thailand; again, a naming process in which I wish I'd had a part].

          "The new study also described other important traits that bats of both suborders share. For one thing, researchers found an “unexpected concentration” of genes involved in repairing damaged DNA. Those fix-it factors, the scientists proposed, are the bat’s solution to the blistering demands of flight.

When a bat flies, its heart beats an impressive 1,000 times a minute, and its metabolism ramps up 15-fold over resting rate. By contrast, said David Blehert of the United States Geological Survey’s National Wildlife Health Center in Madison, Wis., the metabolism of a running rodent is seven times normal, “and that’s only for a short burst, whereas a bat can fly at 15-fold metabolic rate for hours.”

           All that fiery flapping ends up generating a huge number of metabolic byproducts called free radicals, which could mutilate the bat’s DNA were it not for its extra-strength molecular repair crew. And countering DNA damage happens to be a great strategy for overall health, which could explain bats’ exceptional longevity and apparent resistance to cancer."

          Fiery flapping? Swimming all day? A key for both the Bowheads Whale and the over 1200 bat species appears to be movement. . .and rest. The torpor or hibernating phase of bats' lives are being interrupted as they spend time preening (rather than resting) when the White-nose Syndrome fungus is present. 

           These prolific bats can live up to 40 years with little cancer or exhibiting virus illnesses. . .and overgrooming and lack of rest due to a fungus does them in?! 

Off to rest and rejuvenate,

Steph

HAPPY Mapping and Happy Mapping: Whales, Genomes, and Meandering

           HAPPY Mapping, first proposed in 1989 by Paul Dear and Peter Cook, is a method used to study the linkage between two or more DNA sequences. It is mapping based on the analysis of approximately HAPloid DNA samples using the PolYmerase chain reaction. In genomics, HAPPY mapping can be applied to assess the orientation of various DNA sequences across a particular genome in the generation of a genomic map.

            I stumbled on HAPPY mapping after watching this TED talk about happy mapping. Daniele Quercia talks about finding that more beautiful route to travel along. It may add a minute or two to your commute, but adds immeasurably to your happiness factor.

            Here's a piece of a happy map through Denver:

            All of this brings us to the Bowhead Whale. 

               Researchers are looking at the genome of  Bowhead Whales, the longest-living mammals, to see why they live to over 200 years without a higher risk of cancer or other diseases despite having more than 1000 times the number of cells as humans. According to the article published January 6, 2015, in Cell Reports and described in Science News:

              "The scientists discovered differences, including mutations and duplications, in the whale genes that are tied to cancer, aging and cell division. The results suggest that the whales are better than humans at repairing their DNA and keeping abnormally dividing cells in check. The whales do not accumulate damaged DNA, allowing them to live longer without developing age-related diseases like cancer, says coauthor João Pedro de Magalhães, a gerontologist at the University of Liverpool."

              I can tell them why they are so good at DNA repair and longevity. These great cetacean beasts SWIM all day. . .and they take the HAPPY, happy route.

Off to a happy swim,
Steph