Molly models the eyed-egg stage, while Brendon is wearing the yolk sac that the alevin have. Alevin get their food from their yolk sac. This is a good thing, since they don't have mouths yet!
Once the trout develop into the next stage, fry, they are starting to look more like trout. This stage is when they develop a mouth, which Shaunna is demonstrating.
If you look closely, you can see that Jimmy is wearing the caudal fin and caudal peduncle, which is the powerful muscle that attaches the caudal fin to the rest of the trout's body.
Notice, also, that Shaunna's head now has eyes. Trouts' eyes are on the sides of their heads. This allows them to have a wider range of vision to the side and back to look for food and watch out for predators.
Sydney shows what the complete trout looks like with all the parts.
Thanks, Katrina, for the cool lesson!
We can't wait until our trout hatch so we can see them develop for ourselves!