Hello again,
I am still waiting for the larvae to begin cloning once more. They have taken a break for a while and have not done much since I removed the clones previously.
This larva has a yellow/brown stomach.
Separate from their lack of cloning, however, the larvae are doing something interesting. I noticed that their stomach contents seem to have changed. We feed them an equal mixture of three algae: a red, a green, and a brown alga (Rhodomonas lens, Dunaliella tertiolecta, and Isochrysis galbana). Initially, the larvae had bright red stomachs, likely due to a diet rich in R. lens, however, I have noticed now that their stomachs appear yellow/brown (pictured right).
Larva in diet trials
Perhaps the larvae eat the high quality R. lens when they are younger to boost quick development, but switch to D. tertiolecta or I. galbana as they get closer to settlement. In order to investigate this potential change in diet preference with ontogeny, I spawned more sea stars and set up beakers with 100 larvae in each. One treatment will be fed only R. lens, another only D. tertiolecta, and another only I. galbana. Additionally, we have a treatment which will be given all 3 algae. In this way, we will examine if the larvae fed all three algae transition away from R. lens as they age, but also see what they do if R. lens is the only food source. Right now the larvae do not have stomachs and are very tiny (pictured left), however, within the next couple days they should begin to feed.
Lastly, to follow up on my previous post: Pictured below is an image of the progress of the larval clone who was initially an oral hood (the anterior portion of a larva). Now, as you can see, he has continued developing, has a fully functional gut, and has been eating lots of R. lens.
Oral hood clone has a functional gut.