Hydraire and Skeleton shrimp

Gymnangium gracilicaule
It's wanting to photograph the little balls that I could see on a hydroid when diving in Cape Lahoussay I had a nice surprise looking at the pictures on my computer.
Indeed, I had not seen that hydroids were filled Skeleton shrimp (skeletal caprelles or shrimp) measuring less than one millimeter.
To give you an order of magnitude, the white balls (which I thought to be nudibranchs but are actually modified structures from polyps or hydroids put their eggs or larvae) ... are only two millimeters long. You can imagine the tiny size of these animals.