We write this "letter home" as we sit trapped in our laboratory at
McMurdo Station, Antarctica. We are unable to leave the building
as the station is under Weather Condition One, which means
visibility less than 100 feet and winds greater than 55 knots (it
could also mean windchills colder than -100 degrees F). Why would
two UAB Biology professors find themselves in this situation? We
are here with support from the National Science Foundation
investigating aspects of the chemical ecology of antarctic marine
invertebrates and algae. Our work takes us under the sea ice to
collect marine organisms which we bring back to the laboratory for
experimental use.
To access different marine environments, we travel by tracked
vehicles or, sometimes, by helicopters to a variety of locations in
the McMurdo Sound region. By drilling or dynamiting holes through
the sea ice, or by chipping into natural ice cracks, we don our
drysuits and enter a spectacular underwater wonderland.
Unparalleled visibility, commonly 600 or more feet, allows us
spectacular vistas of a diverse and rich marine community which
includes six foot sponges, giant sea spiders, fields of sea
anemones, and an array of other marine animals and plants. From
amongst this plethora of life we carefully select those organisms
most likely to harbor chemical compounds which defend them from
predators or competitors. We bring these organisms as well as
their potential predators and competitors back to the laboratory
where we can study the chemical interactions between them. Over
our many trips to Antarctica we have discovered a number of unique
chemical relationships between these organisms. In addition,
working with a Natural Products Chemist, Dr. Bill Baker of the
Florida Institute of Technology, we have identified a variety of
novel chemical compounds. Although the focus of our work is on the
ecological importance of these compounds, we also make them
available for drug discovery research. For example, one of the
compounds isolated from a sponge during our last trip to Antarctica
shows promise as an antitumor agent.
Even though severe
environmental conditions like those we are experiencing today can
make the work difficult, we find this research and its implications
exciting and rewarding and look forward to describing this season's
results in our next letter.
First, we have made substantial progress in our pursuit of novel
ecologically-relevant metabolites, especially with respect to their
antipredator role. For example, we have found that in Antarctica
sponges are extremely vulnerable to predation by sea stars, and
thus, sponges have evolved a suite of metabolites that prevent
attack by this predator. Interestingly, we have just discovered
that some of these compounds inhibit the digestive enzymes of the
spongivorous sea stars. Another role for such compounds we have
discovered this field season is in the inhibition of overgrowth by
microscopic algae. This is a particularly important problem in
antarctic waters where dense blooms of these algae occur
seasonally. We have also been examining a relationship between sea
urchins and macroscopic algae. These macroalgae are chemically
defended from being eaten by sea urchins but the sea urchins choose
to cover themselves with plants which have been torn loose, thereby
preventing the sea urchins from being captured and subsequently
consumed by their major predator, a large sea anemone. The algae
benefit in turn, being held by sea urchins at depths where they can
still photosynthesize and reproduce. This is an intricate and
complex form of mutualism.
As much as we look forward to our impending return to UAB we are
very excited by the scientific discoveries we have made during this
trip as well as by the stark beauty of our antarctic environs. As
we helicoptered back from Granite Harbor this morning along the
edge of the sea ice, we followed a pod of 30 killer whales hunting
for penguins in the shadows of volcanic Mount Erebus. Such
memories will accompany us back to UAB where we will continue
studies of chemical relationships begun here in Antarctica.
Jim McClintock
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Jim McClintock
Professor of BiologyChuck Amsler
Assistant Professor of Biology
Since we last wrote to you describing our NSF-sponsored
studies of the defensive properties and pharmacological potential
of secondary metabolites in antarctic marine organisms we have been
able to write several new chapters of our developing story. Letter Home Part II
November 15, 1997
This "letter home" comes to you within hours of our return by
helicopter from a remote field camp our research group has
established 75 miles across McMurdo Sound at the foothills of the
Transantarctic Mountains. Situated at the base of massive cliffs
of granite, and aptly named Granite Harbor, our encampment of tents
sits on six feet of sea-ice, providing ready access via snowmobile
to numerous ice cracks. Through these cracks we dive to collect
sponges, soft corals, mollusks and algae for our ongoing studies of
their chemical ecology.
Chuck Amsler