Thursday, August 23, 2012

Jellyfish: A problem in the laboratory

Medusae (Jellyfish) have been in the news lately. And they've also been on my mind.  I'm currently working on a chapter in my dissertation that deals with early marine physiologists and their struggles to keep jellyfish alive in the laboratory for experimental purposes.

The world of jellyfish is extremely diverse.  Blow your mind by checking out Alfred Goldsborough Mayer's three volume Medusae of the World. Mayer, the foremost expert on medusae in the early 20th century and the original founder and director of the Carnegie Institute's Tortugas Laboratory, was interested in the the nerve physiology of jellies. His questions revolved around nerve stimulation and bell pulsation- why does a jelly pulse? Does it have something to do with the temperature of the water? What about the salinity? Does nerve conduction start in one part of the organism?

To try to answer these questions, he had to bring jellyfish into the laboratory. But this was easier said than done. Keeping these organisms alive in aquariums took some work- earlier attempts at keeping them in labs resulted in death of the organism between 1 and 48 hours of their captivity. Some developed white sores on their bodies; other simply stopped pulsating, settled at the bottom of the tank, and expired.

As marine laboratories were founded in subtropical and tropical waters, new species came to the attention of   biologists.  In 1892, W.H. Brooks detailed Johns Hopkins new laboratory space in Port Henderson, Jamaica. One of the interesting aspects of the location, according to Brooks, was the discovery of a "true Cassiopeia" jelly found in shallow, murky lagoons in the area.  He proposed to name it Cassiopea Xamachana. 

The regular environment for the jellyfish was a warm, stagnant pool of brackish water in mangrove swamps and tidal shores.  It could live in fresh or salt water and seemed to thrive in whatever environment it was found.  Biologists could put them in glass jars with no running water, or aquariums with regularly circulating water, and they survived and thrived. A plus side:  they have a very light sting.

This organism would prove to be an incredibly important find for nerve physiologists such as Mayer. By locating their work in the tropics, they could collect Xamachana at the beginning of the season, and work on them until the end of the summer. Instead of struggling with keeping other species alive, they could utilize C. Xamachana. 

This species was not the only jellyfish used in nerve experiments, but it became very popular- and still remains important in aquarium exhibits and scientific research. I explore this species, and other ways that biologists found to work on medusae in the laboratory in my current chapter.

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