Introduced diseases and their impact on people and wildlife

Dr. Sam Bowser

Wadsworth Center, Department of Biological Sciences

This is the recap of a talk given at the Feb 8, 2004 CDHS monthly meeting.

Our February meeting celebrated Charles Darwin’s birthday, and as the icing on our “Happy Birthday Charles” cake we had the pleasure of Dr. Sam Bowser describing his searches for “Evolutionary Clues in the Antarctic Depth.” Prof. Bowser is with the Wadsworth Center department of Biomedical Science at SUNY and the NSF (National Science Foundation).

These evolutionary clues are provided by Foraminifera, which Prof. Bowser characterizes as “Ancient Assemblers and Dismemberers.” He began his lively illustrated presentation by answering the question: What are foraminifera and what is their significance? They are one-cell organisms which have been around since before the “Cambrian explosion” and whose descendants are present today. Firstly, this makes them important subjects for evolution research, in particular with respect to helping solve the puzzle posed by the “Imperfections in the geological record”, which was Charles Darwin’s most serious concern. Secondly, they display a behavior and produce an excretion which may be turned to practical use.

There are four classes of Foraminifera:

1. The naked type whose cell has no shell and just sends out pseudopodia (worm-like feet) to feed;

2. The type which develops a leathery shell around the cell and extrudes the pseudopodia through holes in this shell;

3. The type which gathers small particles, like sand grains, from the environment and assembles these to form the shell;

4. The type which produces an excretion that contains calcium carbonate and solidifies as chalk to form the shell.

The most interesting of these is type 3. Their fossil record has been discovered in the 19th century and dated back to the Cambrian period about 350 million years back. Though they are one-cell organisms, they form tree-like structures up to an inch in size, sometimes even larger. The foremost microscopic biologist and paleontologist of the late 19th century, William Carpenter, drew Charles Darwin’s attention to these creatures and received a kind answer from Darwin. Prof. Bowser displayed a facsimile of Darwin’s letter.

Type 3 poses interesting questions, e.g. “How does a foraminifera know where to put a grain it picked up to make a decent shell?

Today, a descendent of this type of foraminifera is found at only one place in the Antarctic on the bottom of the Sea, 300 feet off the coast under 12 to 15 feet of ice. It is there where Prof. Bowser and his group dives for these foraminifera each year. He vividly described and illustrated how they go about doing this, starting from the drilling a starter hole, extending the hole diameter so that divers can get down, by blasting (much less harmful to the environment than one may think, even less than melting would be), the diving, the sucking up of about one inch of the top layer of the ocean floor which contains plenty of the foraminifera, and initial examination in a Petri dish.

To explore the evolution of the foraminifera one has to compare the different species with respect to: Behavior, Biochemistry, Structure, and Genetics.

Behavior includes the question what do they eat? They extend their pseudopods and gobble up bacteria, algae and the like when they are offered. (No surprises here).

Next question: By whom are they eaten? The sediment abounds with little creatures which look perfectly capable of cracking the shells of the foraminifera and eating their cell proper. But surprise! The creatures thought to be the predators were eaten up! And the foraminifera devoured even their own kind! What makes them so ferocious are threads they spin between their pseudopods consisting of a sticky material of a high tensile strength which catches the prey the way spiders do. Prof. Bowser here used the term “evolving advantage of small creatures.”

These interesting results, however, do not answer the question when and from where did the foraminifera evolve? To get an answer to this (Darwinian) question, the researchers turned to Genetics. As the vehicle, they used a part of a specific gene, the SSU-gene which occurs in all animals, and compared small sections of this gene from the four types of foraminifera. They could not detect a timely staggering between the four types – they all existed simultaneously.

Fortunately, it is also possible to pursue the makeup of the SSU gene back in time, requiring a time-calibration. This is accomplished by determining the number of mutations per generation, using fossil records during the known paleontological time scale. Including all available fossil records including very primitive life forms lead to 4.5 billion years, which is doubtful. But if one “clamps” the time frame not to include these, an age of about 850 million years results for the foraminifera. Taking into account the newest dating of the Cambrian period, may extend this age to a little over 1 billion years. Regarding the impact of the foraminifera on the evolution of multi-cell organisms, Prof. Bowser put forward the following interesting hypothesis:

To stand a chance against the ferocious foraminifera, organisms must be multi-cell to become more versatile and adaptive. Once this process had started successfully, the avenue was open for a fast growing variety of multi-cell organisms and this happened at the start of the Cambrian period.

Coming back to the capability of the foraminifera to build their shells in a quite intelligent manner, and the astonishing properties of the network of the threads the foraminifera are able to produce, the question arises if foraminifera can be put to a practical use. Dr. Bowser in particular thought of nanotechnology, where it is not yet possible to assemble structures in the nanometer range. Maybe, he proposed, it will be possible to train or breed and “genetically engineer” foraminifera some day to do the assembly of nanometer structures. In Lab experiments, foraminifera were deprived of their originally built shells and offered small glass beads (size in the micrometer range), from which they build new shells with a surprising precision.

The interest of the audience was evident is an extensive and spirited discussion after the talk.

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