Caves as Islands

Kate AndrusLecture 29

April 12, 2004

Definition of an Island

1. Abbr. Isl. or Is. or I. A land mass, especially one smaller than a continent, entirely surrounded by water.

2. Something resembling an island, especially in being isolated and set distinctly apart from its surroundings.

Biological Interest • Caves are isolated:

surrounded by different environments

• Isolation leads to adaptive radiation – Selective pressures are more easily identified.

• Can be used, as with normal islands, to investigate evolution

Cave Formations

• Ice Caves

– Carved by melting and freezing of water over time

• Limestone Caves

– Water Formation

– Stalactites, Stalagmites, Gypsum formation

© Peter Lane Taylor / Visuals Unlimited

Types of Cave Organisms

Troglophiles • “Cave Lovers” – these

organisms can ONLY complete their life histories within caves

• Examples: Segmented worms, snails, mites, pseudoscorpions, cave crickets

Types of Cave Organisms(continued)

Troblobites

• “Cave Dwellers” – These organisms can pass their life within a cave (if there is sufficient food) or in the cool areas outside the cave.

• Examples: Flatworms, eyeless cave shrimp, eyeless fish, cave beetles

Definitions courtesy of Mammoth Cave National Park website

Types of Cave Organisms (continued)

Trogloxenes

• “Cave Guests” – organisms that cannot complete their life history within the cave

• Examples: Crickets, bats, pack rats, flies and gnats

Types of Cave Organisms(continued)

Incidentals:

• Can enter caves occasionally

• Examples: Raccoons, frogs, HUMANS.

Selective Pressures and Adaptations

• Darkness – Leads to sensory compensation

• Limited Resources – Results:– Small Populations

– Low, slow reproduction• Cooper 1975 – only 2 out of a population of 900 cave crayfish

reproduced in a period of six years.

– Metabolic Economy• Burbank et al. 1948 – cave crayfish could survive 3.5 times

longer than surface crayfish in the same amount of oxygen.• Dickenson and Franz 1980 – cave fish have lower gill

respiration rates and longer ATP turnover than surface species.

Now, on to the cool stuff!!(What sets these species “distinctly apart” from the norm)

Blind Mexican Tetra – loss of working eyes and pigmentation

Cave Crayfish

• Reduced eyes

• Lack of pigmentation

• Reduced metabolic rate

• Reduced egg production

• Sensitivity to water quality

• Can live up to 75 years

• Currently endangered due to water contamination by cavers

Cave Crickets• Reduced eyes• Elongated feelers to “see” in the dark• Possibility of an oscillating clock not tied to circadian

rhythm in similar cave insects – stresses importance of a periodic rhythm in ALL organisms life-cycles

Sterile Waters ??

• Previously thought of underground cave springs as sterile waters.

• Some waters were often drunk as curative waters.

– Thermal waters in Hot Springs National Park thought to be sterile and a disease preventative.

New Findings• Waters are NOT sterile –

we just did not have the technology previously to see the microbes living in it.

• All cave waters contain tons of living organisms– more than 50% cannot even be identified to genus level.

Shaping of Caves• Microbes have implications in

the shaping of caves.

• Snotties emit sulfuric acid and other microbes consume oil to produce H2S which, when combined with ground water, produces sulfuric acid.

• Sulfuric acid in turn dissolves limestone to carve out 5% of the limestone caves including Cueva de Villa, Carlsbad and Lechuguilla.Snotties - © Peter Lane

Taylor / Visuals Unlimited

Geology or Biology

• Many cave formations previously thought to be created by strictly geologic processes are also now known to have biological bases.

• Examples: travertine formation outside hot springs, gypsum formations within caves.

Gypsum from Mammoth Cave

Problems with Studying Cave Microbes

• In the past, people did not know the abundance of the micro-organisms in caves.

• Even when they were discovered, biologists had trouble collecting and growing samples outside of the cave environment.

• Dr. Larry Mallory – created and perfected methods in sampling, isolation and growth these cave organisms.

Implications in Medicine

• New organisms are often instrumental in developing new pharmaceuticals.

• With the new success in the growth of these extremeophiles outside the cave habitat, research into their medicinal properties has occurred.

       

Immense Diversity • Research by Dr. Mallory has

shown that the microbes in one cave pool can be entirely different from another pool only a hundred meters away.

• This evidence shows the great abundance of new microbes with which they can work in searching for new medicines.

Cancer Research – Biomes Pharmaceuticals

• Microbes are tested on a scale of one to five, five being the strongest.

• Control – five samples of normal soil produces about one Level 2 hit.

• Cave samples – five random cave samples produced four hits: three hits at Level three and one hit at a Level four (unprecedented at the time).

Conclusions*Caves can be seen as islands

-An extreme environment that displays strong selective pressures

-helpful in examining adaptation and evolution in organisms

* Biological organisms seem to be more complex and diverse -There are an abundance of unclassified microbes.

-Their influence on the creation of caves and cave formations.

* Cave diversity has also led advancements for cancer and other pharmaceutical research.

-The hypothesis is, that due to the extreme conditions of caves, these organisms will show novel adaptations to conditions.

- Ultimately, cave organisms may help solve medical mysteries.

Questions??

Bibliography• Brucker, Roger and Richard Watson. The Longest Cave. New York: Knopf, 1977.• Cahill, Tim. “The Splendors of Lechuguilla Cave.” National Geographic 179, 3 (1991):

34.• Culver, David C. Cave Life: Evolution and Ecology. Cambridge: Harvard University

Press, 1982.• Halliday, William. Depths of the Earth. New York: Harper and Row Publishers, 1976.• Jackson, Donald. Underground Worlds. Virginia: Time Life Books, 1982.• Mohr, Charles and Thomas Poulson. The Life of the Cave. New York: McGraw Book

Company, 1966.• Oda, G. A., et al. “Coupled Biological Oscillators in a Cave Insect.” Journal of

Theoretical Biology, 2000. • Taylor, Michael Ray. Dark Life. New York: Scribner, 1999.• Stone, William. “Cave Quest.” National Geographic 188, 3 (1995): 78.• Yoshiyuki Yamamoto, William R. Jeffery “Central Role for the Lens in Cave Fish Eye

Degeneration” Science, Vol 289, Issue 5479, 631-633 , 28 July 2000• http://www.norwebster.com/speleoscope/speleo01.html• http://www.pbs.org/wgbh/nova/caves/about.html• http://nature.org/initiatives/programs/caves/animals/art9279.html• http://www.cr.nps.gov/mwac/field_seas_2003/buff3/cave_crickets.html• http://www.visualsunlimited.com/browse/vu280/vu280831.html• http://www.biomespharma.com/larry.htm