Hello again to everyone! Things have been going pretty well down here although the past several days have made it impossible to go out diving. Due to no diving, I have been able to spend more time in the lab (Chuck likes that). One of the things that I do in the labs is test the palatability of some of my sponge extracts on sea stars.
The fact is, sea stars are a major predator here in Antarctica. They are also very plentiful and don’t move very fast making them a lot easier to collect and then study. The scientific name of the sea star we use is Odontaster validus and often has coloration that is somewhere between red and purple. It is one of if not the most important predator in shallow waters all around the continent of Antarctica.
The individual Odontaster validus that we predominantly work with in experiments here are usually no larger than my hand with fingers extended. Obviously, the younger ones are smaller and we try not to collect them. We mainly want ones with long arms.
One of the first things we had to do once we got down here was collect a lot of these sea stars. The reason is that we have a lot of these feeding experiments going on and need lots of individuals to test. We set up a large circular tank in the aquarium and then start adding sea stars we collect on our dives. As you can see from the picture, we have a good number of them in our tank right now but we would like to have more so will continue to collect them and add them to the tank. Just so everyone knows now, we release them at the end of the season and they are able to survive. Most likely, some of the stars we are using this year were also used last year and released at the end of the season.
I am not going to go into detail about making up the food that I feed to the stars because that can be another journal entry later in the year (and it is also pretty boring, although you didn’t hear me say that!).
Once I have the food that I am going to test, I take it out to the aquarium. I showed you in a previous journal entry what I wear when I am in the aquarium building. So, I am all ready to go and then the most important step comes up…what music do I want to listen to while feeding the stars. Let’s just say that when I put my music on, most of the rest of the group stays out of the aquarium until I am done!
The sea stars are good test subjects because they come to the air/water interface and extend their arms out over the surface of the water, thus exposing their chemosensory tube feet (think of these as the sea stars taste buds) and mouth.
Well, I place a piece of food in between the end of their arm (which has these tube feet running all the way up to the tip from the mouth) and see what happens. If the sea star likes the piece of food, then it moves it toward its mouth. If it does not like the food, then it will toss it off the side of its arm or pull in its tube feet and let the food drift away. On occasion the sea stars will actually start moving back down the wall trying to get away from the food (we know these items are particularly distasteful then).
I do this with one food item until I get a sample size that is sufficient (greater than 10 if possible). Every food item I test is compared to a control item that we know is palatable to the sea stars so that we can disregard all of the sea stars that might just not be hungry.
I know I did not go into all that great of detail on this process, but I wanted to give you that main idea…and I am about to head out to the aquarium to feed some more of the stars. The title of this entry lets you know when I am usually out feeding the stars. Most people know that I am a “night owl” and so I usually work late into the night. It is now 10:30 P.M. here and I figure I will be up for another 2-3 hours and then get to bed.
If you have any questions about the process or want more information, please send a comment and I will do my best to answer all that come in.
Hope all is well where ever you might be reading this and continue to send good wishes down here to us because they are always appreciated.
-Kevin…oh yeah, Go Blazers!