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Monday, July 6, 2015

A glimpse of green

Isn't that an amazing color?  Some people have called it "grass-green."

Do you know what type of animal this is?

The next image provides a more complete view:

This fish was swimming in and out among the Feather Boa Kelp fronds.

My best guess is that it's a Penpoint Gunnel (Apodichthys flavidus).  I had a little trouble with it, because there aren't many gunnels with horizontal stripes from the mouth to the eye.  I eventually found one reference that mentioned juvenile Penpoint Gunnels can have that type of marking.  However, if you think it's a different species, just let me know!

A couple of interesting facts about Penpoint Gunnels:

- After the female lays a cluster of eggs, the male will guard them for ~2.5 months until they hatch.

- They're known for displaying a dynamic color polymorphism.  Individuals can be green, red, or brown.  One research study figured out that the color depends on where the juvenile fish settles and how much light is availablethat is, if it settles high in the intertidal zone in shallow water, it will be green; but if it settles low in deeper water, it will be red-brown.  (It doesn't matter what type of algae is in the background.)

Watch for these beautiful eel-like fish among the seaweeds and cobbles along the shore.


James said...

Are there any hypotheses about what directly causes the color polymorphism (diet, light-activated pigments, or even different physical forces between deeper water and the high intertidal)?

Jackie Sones said...

Hi, James! I haven't ready any hypotheses about that...but it's very interesting to think about! The author of the paper I read mentioned light availability as a possible trigger, but that still doesn't completely explain the exact mechanism for the color determination.

If you're interested, here's the reference:

Winkler, P. 1988. Environmentally induced color polymorphism in the Penpoint Gunnel, Apodichthys flavidus (Pisces: Pholididae). Copeia 1988: 240-242.