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Explore21: Finding Fluorescent Fish

by AMNH on

From the Field posts

A few months ago, Curator John Sparks and team set out to the Solomon Islands on the inaugural Explore21 expedition to explore mysterious organisms that light up the ocean (as well as to study uncharted microbial life and the rich diversity of fishes, corals, and other animals). After collecting fishes on dives or through midwater trawling, the real work on the research vessel, the Alucia, would begin: processing specimens, including photographing a variety of fishes in on-board tanks using specialized equipment.

The first set of photos, taken under white light, capture the fish's coloring as seen by the human eye. The second shot, taken in the dark with special filters, reveals biofluorescence—which Sparks and colleagues have recently reported to be surprisingly widespread and varied in terms of color and pattern among marine fishes. Below are just a few examples of some of the specimens Sparks and colleagues collected on the trip.

Under white light, some species, including the Eviota goby below, appear relatively plain. 

Eviota Goby Fish Under White Light
© AMNH/J. Sparks/R. Schelly/D. Roje

Under fluorescent light, however, unique patterns emerge. Researchers think that fishes like the gobies of the Eviota family may use such distinct patterns to identify members of their own species. In fact, among many closely related species, including within the Eviota genus, researchers observed that fluorescent patterns appear more distinct than coloring or patterns that are visible under white light.

Eviota Goby Fish Flourescing
One of Sparks' interests is biofluorescent fishes like the goby pictured here. 
© AMNH/J. Sparks/R. Schelly/D. Roje


Wrasses comprise a large and diverse family, Labridae, with more than 600 species. Many are brightly colored, but the species shown below has little to excite the human eye.


Wrasse Under White Light
© AMNH/J. Sparks/R. Schelly/D. Roje

When researchers examined the same fish for fluorescence under blue light, however, they discovered a rare wrasse that fluoresces quite brilliantly.

Wrasse Flourescent
© AMNH/J. Sparks/R. Schelly/D. Roje

Some species of sea breams, including the one below, have unique patterns that are plainly visible in daytime. 

Bream Under White Light
© AMNH/J. Sparks/R. Schelly/D. Roje

As it turns out, these racing stripes are also incredibly fluorescent. The pattern may play a role in helping to camouflage this common reef species, making it possible for the fish to blend in with fluorescent coral branches and hide from predators. 

Bream Flourescent
© AMNH/J. Sparks/R. Schelly/D. Roje

Bioluminescent patterns among fishes are incredibly varied. Some species, including eels, fluoresce only in certain body parts, such as the head and tail.

Chlopsid Eel Under White Light
© AMNH/J. Sparks/R. Schelly/D. Roje

But in other eel species, including in the chlopsid eels (shown above and below), researchers have found bright fluorescence throughout the entire body, indicating that these organisms produce high levels of fluorescent protein. Such proteins could have a variety of applications in biomedical research.  

Chlopsid Eel Flourescing
Biofluorescent fish like this chlopsid eel absorb light and then re-emit it as a different color.
© AMNH/J. Sparks/R. Schelly/D. Roje


For more about John Sparks' and colleagues' latest research about widespread biofluorescence among fish, which identified more than 180 species that glow in a variety of colors and patterns, watch this video and read this related post.