I recently decided to get back into observing microorganisms and collected some Spirogyra algae from my backyard biotope. To my surprise, I found an unexpected bonus — medaka (Japanese rice fish) eggs!
These eggs were laid by medaka that had overwintered in the biotope. They were attached to the algae by fine hair-like filaments. I had read that medaka use these filaments to anchor their eggs to aquatic plants and algae, but this was my first time seeing it in real life. I didn’t expect them to be attached with so many hairs — it was quite impressive.
The black, round spots are the developing eyes, and the white, round area below them seems to be the yolk. Occasionally, the embryo twitches slightly, although it stayed mostly still during filming.
Interestingly, I noticed the same dark pigment clusters on both the surface of the eggs and on the baby fish’s body. I hadn’t expected to see pigmentation on the egg surface itself. There are also orange pigments visible on the egg, which seem to give the whole egg a yellowish appearance. I wonder if these pigments serve some specific purpose?
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Microscope: Olympus BH2-UMA
Objective lens: Olympus NeoSPlan 10 NIC
Relay lens: Olympus NFK 2.5×
0.7× reducer adapter
Camera: Sony α6300
Focus stacking: Helicon Focus 8
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