April 28, 2011 | David F. Coppedge

More Complexity in Simplicity Found

Primitive things aren’t.  That seems to be a common thread in some recent stories that found more complexity in simple living things.

  1. Box jellyfish eyes:  Jellyfish are among the simplest of animals, so why do box jellyfish have two dozen eyes but no brain?  Some of these eyes have now been found to detect features above water so that the animal can stay in its mangrove habitat (see New Scientist, Live Science and PhysOrg).
        It is baffling how an animal lacking a central nervous system can receive visual input and respond with coordinated movements.  One marine biologist told New Scientist, “We have an under-appreciation for how sensory systems in simple organisms are used for fairly sophisticated adaptations.”  Another agreed in the Live Science entry: “This shows that the behavioral abilities of simple animals, like jellyfish, may be underestimated.”  See also 05/13/2005 about the box jellyfish eyes, and 11/19/2009 on the lack of an evolutionary explanation for this phenomenon.
  2. Innate immune system:  “Compared to the sophistication of the acquired or adaptive immune system, the innate immune system was considered a rather simple and blunt instrument,” said an article on MedicalXpress.  No longer; Scientists at Max Planck Institute were astonished to find that neutrophils, part of the innate system, are able to spread elaborate networks of DNA-histone filaments to capture intruders.  “When scientists can’t believe their eyes, it is very likely that they are on to something quite extraordinary,” the lengthy article began.
        Neutrophils were found to form NETs (Neutrophil Extracellular Traps) when summoned to an infection site.  “Under the scanning electron microscope, the NETs appear as fine fibers and particles that link the threads to form more complex structures,” the article said.  “This causes the formation of a ball in which the bacteria become engulfed.  The main ingredient of this ball is chromatin.  This mixture of DNA and proteins is normally found in the cell nucleus and contains genetic information.
        The unexpected discovery of complexity in a “simple” system subsequently led to other fruitful leads about how the immune system operates, and how serious diseases ensue when mutations muck up the works.  The adaptive immune system is even more complicated.
  3. Proteasome:  The disposal of protein “trash” in the cell is the job of a complex machine called the proteasome.  What could be more mundane than trash collection?  Even there, sophisticated mechanisms work together.  PhysOrg described a new finding that shows that “two different mechanisms are required to determine which targets to destroy.
        The “recognition tag” and “initiator tag” both have to be aligned properly to enter the machine’s disposal barrel.  “The proteasome can recognize different plugs,” a researcher at Northwestern University said, “but each one has to have the correct specific arrangement of prongs.

Speaking of cell machines, a new video of actin filaments was produced by scientists at Yale and Grenoble, France (see PhysOrg).  “Thread-like actin filaments, strong as commercial plastic, are the muscular workhorses of our cells — pushing on membranes to move cells to the proper location within tissues and applying pressure within the interior to keep all working parts of the cell where they need to be,” the caption said.  “These filaments do their jobs through a mysterious process of continual splitting and reassembly.”  The video shows the splitting process.

Essay question: which world view expects more simplicity in the lower forms of life?  Which world view is usually wrong?

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