22 October, 1996
One of my responsibilities on Tuesdays is to feed the anemones that we use in bioassays. Once a week they get one freeze-dried krill. An anemone looks more like a plant than an animal. It has an array of tentacles that move above its body like branches on a bush. The tentacles move through the water column and wrap around objects that touch them. It has a mouth in the center of the ring of tentacles which it shoves its prey into along with its capturing tentacles. They look like they are licking their fingers after a meal.
The anemones, along with a number of other organisms, are kept in an aquarium building near the ice edge. Typically Jim, Pat, or scientist from other groups conduct experiments with the animals that are housed there. I saw several rather strange creatures that I didn't recognize. One looked like a white slug. I asked Pat about it and why it had been collected. I also asked him if he would write about his experiment. He decided we should include some pictures and identify the body parts of the organism he was studying. Getting the pictures that I've included took me the rest of the evening. This is great for me, every day is a new learning experience.
Pat Bryan's work with Nudibranchs
"I am studying both juvenile and adult nudibranchs or shell-less snails called Tritoniella belli. These are organisms that obtain chemical defenses through their diet. The juvenile shown is about 5 millimeters long and the majority of its body mass is covered with cerata or gills. The adult stage is also shown. A juvenile is defined as the developmental stage of an organism that follows larval settlement or hatching from an egg, yet proceeds adulthood. Adulthood is defined by reproductive maturity. Juveniles often occupy distinctly different ecological niches than adults of the same species. They often eat different foods, live in different microhabitats, and have different predators than adults. Yet because of the small size and often-cryptic (hidden) behavior of most juvenile marine organisms, very little is known about them.
In the Antarctic, performing research in the field is extremely difficult, especially when you are diving to a depth of 100 feet in water that is -1.8 C. Fortunately, I managed to find juveniles of the Antarctic nudibranch Tritoniella belli hiding among the branches of an Antarctic hydroid. Nudibranch's often incorporate chemical or structural defenses from their diet into their tissues. However, the mechanism of "borrowing" defenses from other organisms is poorly understood. By studying juvenile nudibranchs we may be able to determine how these types of mechanisms develop and are used by the adults.
My specific interests concern the development of chemical defense strategies in marine invertebrates. I want to find out if organisms that possess some type of a defense as an adult possessed this same defense all their life or if the defense is specific to the adult stage. Moreover, if juveniles do have different predators and diets than adults of the same species, they may utilize different defensive strategies than the adults. Hopefully, I will be able to determine if juvenile Tritoniella belli can defend themselves from predation and if this defense differs from the defense strategy used by adults. If the defenses are different, I would like to find out how and when the change takes place. With the help of everyone in S-022, we will find out all about this nudibranch during this season on the ice."
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