Day 2: Where are my larva?

Today our larva hatched from their eggshell and began crawling around.

Students were first asked to recall and attempt to diagram the anatomical positions (anterior, posterior, dorsal, ventral, lateral) on pictures of 3 different stages of development (embryo, larva, adult) as well as identify which stage was which picture.

We then showed students a video from DNATube that showed the development of the embryo to the first instar over the last 24 hours. Basically, we wanted students to understand that something was happening between yesterday and today and it has a really good time-lapse of segmentation, folding, and migrating of cells in it as well.

Students then found their apple juice agar plates from yesterday and looked to see what had happened over night. To their surprise, “nothing had happened” because their eggshells, including dorsal appendages, were still present. This was an unexpected moment on my part, but they thought their flies had died. It finally took a student or two shouting, “I found some moving!” and with some prompting they described they were by the yeast paste, not their eggshells (which most had forgotten were shells and not part of the epithelium that grew with the fly. After that hurdle, most students began making great observations, observing feeding, movement, social behavior between multiple larva.

Once students had observed and documented the change in their larva, we then moved to adults so students would be familiar with them since they will have adults next week when they set up their crosses for over winter break. First, we reviewed what male and female fruit flies looked like (Freshman had been assigned to watch this video last night; AP was given the task of figuring out by using observations and the internet which sex was which) and then they were given the task of sorting through about 15 flies we had put to sleep with FlyNap in petri dishes into male and female groups. If you need a refresher, here’s a photo (this was also a good example of why we discouraged students from using size as a determining factor for sex):

Some students even got to witness the miracle of life (can you figure out the sex now?):

After separating male from female it was about time to go so with our last couple minutes we asked students to share their observations about what was SIMILAR between all of their fruit flies and to my astonishment about every class had the two picked out very quickly. That would be the orange eyes and curly wings, which are mutant phenotypes (wildtype being red eyes and straight wings). We left the freshman with that and told them we would discuss further their genetics on Friday while AP students were given the task of beginning to research Balancer Chromosomes, with the tip that this was essential to understanding these mutations, since they had a little more time left.

Tomorrow and Thursday are off days, we’ll be back researchin’ on Friday!