Rudimentary

Our Strongylocentrotus purpuratus urchin larvae (fertilized 4/1) are on the verge of a radical lifestyle change. An outpocketing of the left hydrocoel (featured in previous posts) is starting to look suspiciously like an echinoderm, pentamerous symmetry and all. This so-called 'rudiment' of the adult organism will soon part ways with the bilaterian pluteus and adopt a sea urchin's benthic existence.

Left lateral view, rudiment circled in red.


 Dorsal views, focused close (top) and far (bottom) to show different parts of rudiment.

All photos taken at 200X under DIC illumination.

After depositing the rudiment, the rest of the larva will swim away to...well, we're not sure where. More on this to come, we hope.