Recognizing an Acartia copepod

Acartia copepod

I’m an Acartia nauplius. That means, a young copepod.
I live in the Baltic Sea, near the city of Turku. The researchers in the Archipelago Research Institute caught me a while ago.

… Well, to be honest – I’m not alive any more.
When researchers take zooplankton samples for biomonitoring they add a some formaldehyde in the sample to preserve all the animals for the future. In other words – they kill us. In return they get information about the state of the water and relationships between phytoplankton/zooplankton/fish and many more things.

Acartia nauplius.
Acartia nauplius.

I’m not that big, only 330 µm long. This photo has been taken with a 10x objective. The total magnification of the microscope was 100x, but here the final magnification depends on what size your device gives you. If you see me 3,3 cm long, the magnification is 100x. If you see me 6,6 cm long, the magnification is 200x. So although I’m much small, I’m much bigger than many other fellow planktons. Like many green algae.

You can distinguish me from the other nauplii in the Baltic Sea because I have a flat “forehead”.

I also have two small, straight spine on my bottom.

Acartia nauplius spines.
Two little straight spines on the bottom.


Quite easy to recognize, as soon as you get a hold of it. Other nauplii have rounder heads and more or other kind of spines. We well discuss them in other bloggs. Stay tuned!

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