October Update

Bought a standard poodle puppy.  Bringing him home October 5, so October will be full of housebreaking, and FUN.

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WONDER OF THE MOMENT

Entries in cave (4)

Thursday
Aug262010

Spelunking for a Degree, Part 4: Blind Cave Beetles

Many creatures that live in caves are blind.  Yet their ancestors were sighted.  This is a great example of evolution.

         I did my master’s research on the cave beetle, Ptomaphagus hirtus.  This beetle’s ancestors scavenged for food underneath the leaf litter on forest floors.  Since it’s dark under the leaf litter, eyes were of little use even to these immediate ancestors.  But much earlier ancestors had eyes and used them.

         Though the circumstances differed for the ancestors of other cave animals, like fish or crayfish, the natural selection process was similar.  In the cave, except at the cave mouth, there is absolutely no light.  So eyes are of no use at all.  It takes energy to build eyes, and for living organisms, energy is like money.  The less energy an organism has to expend, the better off that organism is in terms of evolution. 

         Here’s why:  Let’s take my Ptomaphagus beetle.  Like all living things, the Ptomaphagus beetle has to expend energy to mate and lay eggs.  The less energy the beetle expends building and maintaining useless eyes, the more energy it has for building and laying high quality eggs, which lead to successful new beetles.

         “Survival of the fittest” means the most fit beetles will pass on the copies of their genes to more or larger new generations of offspring.  So in a cave, the most fit beetles will be those that lose genes necessary for building and maintaining eyes, for this loss will save energy that otherwise would be wasted.  The very fit blind beetles will pass on all their genes to their offspring, including the mutated eye genes that no longer code for eyes.  Eventually, all the surviving Ptomaphagus beetles will be blind.

          Of course all these blind creatures still must escape predators and must find food, so some of the energy they save in not having vision, must be spent on other senses.  I’ll have more to say about this in my next post.  Stay tuned.



Tuesday
Aug242010

Spelunking for a Degree, Part 3: Incomplete Food Chains & Crickets

The beetles I traveled to the Kentucky caves to collect are part of a cave ecosystem of insects, small mammals such as rats, and various types of fungus. 

         Cave ecosystems contain incomplete food chains.  The start of most food chains consists of producers, usually green plants or algae.  They make food by photosynthesis, using light energy from the sun.  Then other organisms feed on the producers.

         But no light enters caves, so no producer can start a food chain there.  The cave ecosystem requires some creatures to leave, eat vegetation outside the cave, then return with the food, or their own waste from the food.  In the Mammoth-Flint Cave System, animals that go out to feed and return to start food chains are rats and crickets. 

         I was surprised when I first shined my helmet light on the crickets.  They’re about twice the size of ordinary black crickets.  And these cave crickets are pink.  They don’t need protective coloring, because the cave is pitch black, and they leave the cave to feed only at night.  So they have evolved to be colorless, saving the energy it would take to manufacture pigment.  Their pink color is just the natural color of the protein that makes up their exoskeletons.

         Neither the crickets nor the cave beetles I was researching started out in the caves.  Hundreds and thousands of years ago, the ancestors of these insects lived in the woods.  Gradually, some groups of crickets and beetles began feeding exclusively underneath the leaf litter that covers the forest floors.  It was dark under the leaf litter, so the more immediate ancestors of cave crickets and cave beetles adapted to life in the dark even before any of them ventured into caves. 

         Wind, rain, and animals moved leaf litter into the mouths of caves, and the beetles and crickets moved along with the litter.  Gradually, they moved further into the caves.  This favored the crickets, because they could nest in a more protected area with few predators.  It favored the beetles, because they could find a steady food source of cricket guano with less competition from other feeders.  Other animals, as well as various species of fungus may have entered the caves at the same time or before or after.  And so a cave ecosystem was born.

         The caves were a refuge during ice ages when glaciers covered what is now Kentucky.  Life in the cave turned out to be pretty safe as long as a few hearty creatures could venture out to forage under the snow and ice.

         Isn’t it awesome the way every cranny of the earth gets populated?  Adaptation has made even cold, pitch dark caves hospitable for species like bats, cave crickets, and cave beetles.



Friday
Aug202010

Spelunking for a Degree, Part 2: More about Bats

In my last post, I told of the refrigerator malfunction that brought me to the cabins of the National Speleological Society in the Kentucky woods.  I had come with my thesis advisor and another student, to collect a fresh supply of beetles from the Flint-Mammoth caves for my master’s research at the University of Illinois at Chicago.

         But before I captured any beetles, I experienced bats

         Perspiring in winter clothing in the extreme summer heat, we drove up to our first cave entrance.  The Speleological Society had installed a padlocked iron door to the cave, with circular cutouts to allow bats to fly in and out, which a bat did right in front of me.  My thesis advisor unlocked and opened the door, and out flew a couple more bats.  They were nothing like the scary Hallowe’en pictures.  These bats were light grayish brown, and their bodies, rather than their wings, were what we saw.

         Inside the cave, the year-round 50o F temperature prevailed, a welcome relief.  But I was completely taken up with staring at the arching, rocky walls, some smooth, some crenelated, some with natural shelves jutting out.  The overall colors were gray, amber, and pink.  Wearing miners’ helmets with lights on their fronts, we followed natural paths, and human-made stairs from cavern to cavern.  At one point, my professor had us all turn off our lights to experience the dark of the cave.  It was a strange experience: I kept waiting for my eyes to adjust to the dark, expecting to be able to see dimly, as at night.  But, of course, in a cave that never happens, because there is absolutely no light at all.  So all the creatures we encountered in there lived in cold pitch black except when humans came around.

         Then we started collecting beetles in one cavern after another.  Hanging from the ceilings were sleeping bats, no bigger than a child’s fist.  I found these little bats so charming: when they sleep, they allow their body temperatures to cool; so when they wake, they can barely move.  The cavern ceilings were often low, and I could walk right up to a sleeping bat and watch it.  Each bat woke up when I approached with my lighted helmet.  Slowly, the bat would begin to move its body and wings, gradually speeding up until it finally had generated enough heat to be able to move freely.  Now it would unfold its wings, stretching and flapping a bit, until finally, the bat would fly off.

         Let me know how you like cave lore.  I’ll post more about Kentucky cave life next time.



Tuesday
Aug172010

Spelunking for a Degree, Part 1: Bats

There are bats on the cover of a recent edition of Science.  They reminded me of the little gray cave bats I encountered during my research for a master’s degree in biology (specifically, in ecology).

         My master’s research was on a cave beetle, Ptomaphagus hirtus, and the possibility that it was in competition with various fungi that used the same food source.  The food source was rat feces.  The beetles and fungi are part of the wonderful earthly system that clears away this waste material.  Otherwise, after 3 and a half billion years of life on earth, we’d be up to our ears in the stuff.

         The ambient temperature inside a cave is the average of the year-round surface temperature where the cave is located.  My beetles live in the Mammoth-Flint cave system in Kentucky, at a temperature of 50o F.  They’re round and tiny, with a diameter of 2-3 millimeters.  So when I first started my master’s research, I could just use the populations my thesis advisor kept in his lab refrigerator.  The beetles lived in shallow glass dishes about the size of a small cake pan, floored with mud from their native caves.

         At the end of my first research year, I needed to earn some money.  So I took a job teaching middle school math and science, and returned to the lab the following summer to finish my research.  Alas, I walked into the lab refrigerator and came upon a waste land.  The fridge had malfunctioned (with no alarm system), and my beetles were all dead at Chicago summer temperatures.  Thus came about my actual introduction to the Mammoth-Flint Cave system.  The lab refrigerator having been repaired, and an alarm system installed, my thesis advisor and I headed for Kentucky.

         It was hot as hell and the cicadas were buzzing loud when we arrived at the cabins of the National Speleological Society.  Sweating, but dressed for 50o, we drove to the cave where we intended to collect our first beetles.  The Speleological Society kept it locked with an iron door perforated with cookie cutter circles.  These are for the bats, a few of which swooped out even before we opened the door.

         Stay tuned.  I’ll be telling some bat stories, cricket stories, beetle stories from among the underground creeks, limestone florets, etc.