Corycaeus, a "study" of its amazing eyes

Charles Krebs · Post by **Charles Krebs** » Sat Dec 18, 2010 9:17 pm

This summer Franz posted some Corycaeus pictures, and I was really amazed at the eyes that this copepod had developed. I had never seen anything like it. (And when I got online to post these, it looks like Wim may have added one just today!)

Yesterday I took a marine sample in Puget Sound and came across a few Corycaeus. (Could possibly be Corycaeus anglicus which are common in this area.)

I took a few overall shots, but really concentrated on those stunning eyes.

Here I dialed in some colorful DIC. I don't normally do this, but in this case the "optical staining" really did help to show the subject.

I also did some basic cross polarization. It was intriguing that the front component of the eye illuminated in a similar manner to the way muscle tissue responds. Makes me wonder about the optical characteristics...

I never did get a shot I really liked from the top showing both eyes. But in one case a had a view through the ventral side... so I'm looking through a lot of creature here... not real sharp. But what was interesting is that on the ventral side there is the basic red eye-spot so often seen on copepods. And as I focus through to the top you can see the location and outline of the two eyes. So I put two frames together in an animated gif.

Wim van Egmond · Post by **Wim van Egmond** » Sun Dec 19, 2010 2:54 am

Dear Charlie,

Wow, these are just fantastic. I was about to post some images of Corycaeus but mine are not that spectacular. But perhaps I'll post them just to see if they are different species.

Good to see you are doing marine organisms. There is so much to find in the sea. I'l do my best to post a bit more but I may run out of material soon.

Wim

Mitch640 · Post by **Mitch640** » Sun Dec 19, 2010 3:33 am

Amazing images. And a truly amazing animal. I just spent the last half hour reading about him, his predatory hunting success, which can be seen in your images, and about the eye structure of this guy. He seems to be pretty successful as a species, since that binocular forward vision with true depth perception also helps him find mates.

Here's some further reading.

Perl · Post by **Perl** » Sun Dec 19, 2010 4:16 am

Hi Charlie !

Excellent pictures !!

Charles Krebs · Post by **Charles Krebs** » Sun Dec 19, 2010 9:31 pm

Good to see you are doing marine organisms. There is so much to find in the sea.

Yeah... Franz was posting all these neat strange creatures so I thought I would have a look. One "problem" is that you really need to set the time aside to work with the collected samples as soon as possible. It's not like a fresh water pond where it can sit on a window sill for as few days.

Wim van Egmond · Post by **Wim van Egmond** » Mon Dec 20, 2010 12:21 pm

That's the trouble with marine samples, They only last a couple of days. I always keep the samples in the fridge in a shallow dish. It is also important not to catch too many organisms. Or also take some more dilluted samples for day number 2 and 3. Save the strong organisms (copepods!) for last. The best way is of course to rent a little house near the harbour and use the microscope there. Or rent a boat! :-)

Wim