Sunday, July 7, 2013

Leeah: Week 2

This week we focused mostly on molecular work and did some plankton tows on the side. On Monday Terra showed me how to do DNA extractions with some of the larval samples that I had previously frozen the week before. For larval extractions and smaller tissue samples, Instagene is used. This substance is made of tiny beads that hold everything with the exception of the DNA samples. After going through a long process of heating and centrifuging, the beads collect on the bottom of the container and the DNA sample rises to the top where it can easily be removed by means of a pipet. After learning how to do a DNA extraction, Terra taught me how to run a PCR or polymerase chain reaction. This procedure finds a specific segment in the DNA, we use the 16S and CO1 segments, amplifies it and replicates it over and over. Finally I learned to run an agarose gel test. Because DNA is more negatively charged (due to its phosphate backbone I am guessing) it will migrate from a more negative side to a positive side when a current is run through it. After this we are able to put it in a gel imager and with the addition of UV light, we can see how well we extracted the DNA.

 The below image is the results of the Agarose test using the same samples each time. The "After" image was done better as the DNA shows up on all the bars.
Before: July 02--After: July 06
In addition to the intensive molecular work that I have been learning about, Terra and I have also had some time to take two plankton tows. Normally we go when there is a high tide as the waters are able to carry the net out and we just need to hold it. This week we went a little before the tide started coming in and we have gotten much better results. I was very excited on Tuesday to find my very first pilidium larvae in the tow. On Tuesday I had found three pilidia. I kept two of them and froze the third. On Wednesday I found more of them and I was able to freeze two. Terra found about 20 larvae which she categorized into four separate dishes and is now entrusting me to keep alive. Each day thereafter I have been taking pictures of a single more mature larva from these cultures and freezing it as a representative for the entire batch to show how they are growing.

Here are some of the larvae that were caught in our plankton tows this week:
1.  Pilidium larvae close to metamorphosis  2. Captured pilidium larvae (aka "Mr. Squiggles")
3. Pilidium Pyramidum ("Stumpy")  4. Pilidium Recurvatum
I have been very busy this week but I still have had some time to work on drawings. I chose a Red Lineid adult nemertean to draw this week. I did a few short gesture drawings of it coiling and moving. Terra and I then anesthetized it with 50% MgCl2 and 50% filtered sea water. I drew a more detailed ink drawing of the worm and took some close-up photographs of it with the camera attached to the dissecting microscope.

 Here are my sketches from this week:

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