Hi all,

So after a rush to pack and a long flight I'm back in Austin. I still have more to tell you guys about my larvae and experiments though!

First off I want to get you all a little more acquainted with the larvae.

Here is a little something to help you with the scale of how big these guys are. That white thing is a PVC sieve that has a mesh glued to the bottom that allows me to catch the larvae in the bin. In the sieve right now you can see dark little dots (maybe). Those are the larvae!

Here is a video

These larvae that are swimming around are referred to as 'planula'. These planula happen to be really fluorescent! I use a special microscope that uses light and filters to be able to see the fluorescence of the larvae. Remember, the reason these larvae are fluorescent is because they make fluorescent proteins (FPs). FPs absorb specific types of light and then produce (or emit) a different type of light. Corals have many different types of these proteins that result in different fluorescent colors.

Fluorescent A. millepora planula

Sometimes the planula are more green

Sometimes the planula are more red

The color of the planula is determined mostly by the mother. However, even within a family (one mom + one dad = many babies) there can be red and green planula. I'm trying to understand these color differences and how color is related to other larval traits or characteristics.

In addition to my thermal tolerance experiment I want to see if the red and green larvae have differences in metabolic rate and cell number. What I did for this was two things:

I took fluorescent pictures of individual live larvae (such as the pictures above) and then performed a cellular metabolism assay on the live individuals. This uses a chemical that binds to a specific metabolic protein. I'm able to tell how much chemical bound and compare between treatments (in this case, between different colored larvae). 

The second thing I did was take fluorescent pictures of individual larvae at different time points and I will stain the nuclei to count the number of cells. I preserved the individual larvae for this and will do the staining and cell counting at UT Austin this spring! My prediction is that red larvae will have lower cell numbers and lower metabolism than green larvae. 

On to the next cool thing: metamorphosis! These larvae do not stay larvae for very long, about one week (although there is a lot of variation that is interesting in an of itself!). After that, the larvae start to metamorphose into little juveniles, or 'recruits' as coral people call them. Coral recruits are also fluorescent:

Young coral recruits look like little flowers, I think they are super cute! They don't swim anymore, and there are beginning the process now of laying down their skeleton. After they metamorphose, that's it, they can't go back and they are stuck where the land for the rest of their life.

A green and red juvenile who metamorphosed right next to each other. 

A project I started with my friend will look at if the different colors of the juveniles has anything to do with how they begin their symbiosis with algae. You may remember that corals have algae that live inside them that is necessary for them to live (these algae photosynthesize and product essential energy for the coral). A. millepora do not have these algae when they are babies, but instead get them from the environment after the grow. I'm interested if the color of the recruit has anything to do with the time they establish this relationship and the type of algae it ends up associating with. It's pretty much a long shot, but I thought it'd be fun to try anyway! Besides, taking pictures of the little recruits is kinda fun.  

That's all for now! I'll see ya'll soon!