An Amazing Metamorphosis

by AMNH on

From the Field posts

Exploring Flatfishes on the Explore21 Expedition

This month, Museum Curator John Sparks is leading The Explore21 Solomon Islands Expedition. A part of the Museum's Explore21 initiative, this three-week research journey is headquartered aboard the Research Vessel Alucia.

Expedition member Dawn Roje (second from left, below) recently wrote in with this dispatch.

Explore21 Team Leaves AMNH
In September 2013, the Explore21 expedition team waved good-bye to the Museum, bound for the Solomon Islands. The team is led by Museum Curator John Sparks; and includes Dawn Roje, a Ph.D. student at the Museum's Richard Gilder Graduate School; David Gruber, a marine biologist at the Museum; Eunsoo Kim, assistant curator in the Division of Invertebrate Zoology; and Robert Schelley, from the Museum's Department of Ichthyology.
© AMNH/R. Mickens

Finding treasure during my first two days out at sea is an odd mix of exhilaration and calm.  Exhilaration in finally obtaining the specimens I crossed the dateline for and reassuring in that anything else I collect beyond this point is an excess of riches. 

"Alucia" research vessel at sea in the daytime
The Research Vessel Alucia allowed Museum researchers to explore the waters, mangrove forests, and coral reefs of Solomon Islands in 2013
© AMNH/John Sparks

The animals I am focused on collecting are the larvae and juveniles of what we are used to seeing on our plate at dinner: halibut, flounder, sole, and fluke, the flatfishes. 

Halibut for Explore21 Dawn Roje (Image NOT by her)
Before flatfishes like halibut (pictured) make it to the fish market they travel the world’s oceans as plankton, looking and living quite differently than the adults. Dawn Roje is researching flatfish metamorphosis and collecting specimens in the Solomon Islands. 
Shane Anderson via Wikimedia Commons

Before flatfishes make it to the fish market they travel the world’s oceans as plankton, looking and living quite differently than the adults. As larvae, they appear to be like all other fishes, with an eye on each side of the head. But then something truly amazing happens. Their skull softens, one eye moves over the top of the head, and they begin swimming on their side as they settle out of the water to live the rest of their life hiding in plain sight of the bottom of the sea.

How and why do they do this, you ask?  Well, that is exactly that I am trying to figure out.  I, along with the much-needed and appreciated support of my friends and colleagues, have been collecting different species of flatfishes during various stages of development to study their metamorphosis. From our first mid-water trawl in 600 meters of water off the Solomon Islands, I got a beautiful flatfish larva still swimming upright, but with its right eye inching its way over to the left side of its head.  The very next day on a scuba dive I collected another individual, but this one was a juvenile that had just completed its metamorphosis.

Fortuitously, this all happened in the first couple of days.  This kind of luck is rare, but glorious.  This expedition and these samples make it possible to understand the mechanism of the one of most amazing body plan transformations in biology. Today I am a happy biologist and I can’t wait until tomorrow’s catch.

See all dispatches from the Explore21 Expedition: