Spelunking for a Degree, Part 5: Sensory Rearrangements in the Dark

I’ve been posting about my trip, many years ago, to the Mammoth-Flint Cave System in Kentucky.  I drove down there from Chicago with my master’s thesis advisor to collect research beetles.  But the trip turned out to be a learning experience in itself.

         In my last post (August 26), I pointed out that cave creatures, which evolved from ancestors that lived out in the open, often have reduced or absent eyes.  It’s pitch dark in the cave, so eyes are no use.  And some of the energy saved from eye building and maintenance can improve survival and reproduction.  That means natural selection will favor blindness in cave animals.

         Organisms that live in caves can also save energy on color production.  No protective coloring is needed.  As a result, cave creatures are often colorless, or show only the colors of the proteins they are made of. 

         But the various mammals and arthropods that live in caves must be able to find food.  So they have to replace vision with other senses:  Their hearing, smelling, touching, and awareness of vibration must become so excellent that they can sense predators or prey or inanimate food just as well in the absolute dark as sighted creatures can in the light.  So some of the energy saved from establishing sight goes into building excellent vibration detectors in cave fish, or extending antenna surface area for chemical detection in cave beetles.

         The latter made it difficult to collect those beetles.  Each time I tried to trap one, it veered away.  I had to develop a much better search image so that I could become quicker than the beetles.  The task was even harder because the beetles were completely at home in the 50^o chill, while my hands grew stiff after an hour or so, and I began longing for the summer heat out in the Kentucky woods.

         I am forever grateful for the refrigerator malfunction (see my August 17 post) that sent me down to Kentucky and into the cave on my beetle collecting errand.  It was an invaluable experience.  It made my research beetles much more interesting and gave me new respect for the environment they call home.