Post #4

Some Acanthaster success at last!

I went snorkeling two days ago to a new spot on the northwest corner of the island.  I was eager to check out that part of the fringing reef because researchers returning from there said they saw a lot more live coral there than out front of the lab.  Plus, one snorkeler had counted 19 COT (crown of thorns star fish) in about 1 1/2 hours.  It was a rough day to go, for the weather had changed from day-after-day of calm seas and blue skies to a dark gray cloud cover and higher winds.  The winds caused big swells to develop that crashed on the reef, causing surges and currents in the shallow back reef area where we were snorkeling.  Still, I found 5 COT and brought back the biggest two of them.  Lucky for me, one was a male and the other a female.

The COT are placed in large blue mesocosms (tubs) with running sea water.  When ready to use, I carefully remove a COT while wearing protective gloves.  (The spines still can go right through these gloves and their wounds really hurt for days.) (Yes, my left hand does have a glove on it.)

For a dissecting tray, I use a clean garbage can lid.  One must be resourceful when in remote field stations......

This one had already been operated on.  You can see the white spots that are the stumps of the spines that I cut off to minimize the chance of getting punctured!  Since I need eggs and sperm in order to do my fertilization experiment, I dissect out a few gonads from near the "armpit."  In the COT, there are separate males and females, and the gonads can be found in this armpit region of each arm.  In the ocean these animals "free spawn," releasing their eggs and sperm into the water where fertilization takes place.  I need to have fertilization take place in a test tube, so I remove some of the gonads from "ripe" individuals.

Starfish have an amazing ability to recover from injury and regenerate lost limbs.  The COT, like some other starfish, has been reported to completely regenerate from just one arm (as long as it has part of the central disk area).  Thus I'm assuming these COT will recover after I return them to the reef.

So what to starfish gonads look like?  Take a look:

The orangish frilly organ in the upper right of the cut is digestive gland, the white stuff on the left side of the cut is mostly gonads.   There are many gonads in each arm of the COT.  I remove some gonads and put them in a dish of sea water.

Food storage containers have all kinds of uses!

In the lab, I treat the ovaries with a chemical (10-4 M 1-methyladenine, for those interested) to release the eggs, then add sperm from testes cut up in a bit of sea water.  Put these some eggs and sperm on a microscope slide and Voila!  (this is French Polynesia, after all....) Fertilization!

These eggs are about 0.2 mm in diameter.  The one on the right did not get fertilized while the other two are surrounded by a fertilization membrane, which lifts off the egg after a sperm enters.  Seeing this really excited me, for it means that I now can run all the preliminary experiments needed to fine tune the protocol for my "big" experiments.  I hope seeing starfish eggs excites you too!

(All pictures but the last one were taken by Emily.  The last picture I took through the microscope using an attachment enabling me to mount my SLR on the ocular tube.  Pretty handy!)