We also put a glass tube at the bottom of the tank, thinking that they might try to crawl in there for safety, but we never saw them in there. Basically, they remained very still, except for certain instances in which they seemed to start flailing uncontrollably. They would start swimming around in circles or in figure eights or in some other odd pattern. It was actually quite hilarious to watch. I was not quite sure why they did that, but I guessed that they were looking for something. I later found out that that was true, that they were looking for some sort of protection (like the seaweed).
I made another very shocking and interesting discovery the first time I took a worm out to weigh it. I took it out with a net and put it on a paper towel, and as I was walking to the scale, this "thing" jumped out at me from inside the worm (I literally almost dropped the poor guy!). The only way I can really explain it is if you take a sock and turn it inside-out. The worm basically extended its body by "unfolding" this unknown thing from inside. After the initial scare, I later come to realize that this is called the "reversible probascis" or something to that effect. I learned that the worm uses it to catch small fish when it is hiding in some seaweed. I also observed it later and found little teeth on the end of the probascis. That basically sums up the activity that I noticed.
After observing the worms, I formulated the hypothesis that, when facing a change in salinity, the worms would adapt osmotically to the environment and their volumes would change, but they would not make any efforts to re-adapt back to their original volumes. The reasons I formulated this hypothesis were quite frankly less than scientifically stable. When I looked at the worms, I saw a very basic physiology, and I suppose I figured that a basic physiology like that would be less capable of engaging in re-adaptive processes.
