Marine Resources Center


By Laurel Hamers

Our arms and legs normally work so fluidly that we may forget that their size and location were determined by complex genetic control during early development.

Keys to the precise regulatory ballet that makes our limbs look the way they do may be found in a seemingly dissimilar group of organisms: sharks and skates.

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Skates in the MBL’s Marine Resources Center. Photo credit: Laurel Hamers

Cartilaginous fish like sharks and skates are the oldest fish to have pectoral fins:  paired appendages that are the evolutionary predecessor of our arms. Tetsuya Nakamura, a postdoctoral researcher at the University of Chicago, is spending the summer at the MBL investigating these cartilaginous fish. He hopes to elucidate the molecular mechanisms responsible for the diversity of fin shapes in this single group of fish and, on a broader scale, the evolution of appendage shapes across species.

“The best way to understand the diversity of fin types is to study an extremely strange fish, like the skate,” says Nakamura. “The pectoral fins of skate are very wide—they’re totally different from other animals.”

Nakamura is focusing on Hox genes, which control body patterning during embryonic development; they are responsible, for example, for making sure your arms attach below your shoulders and not out the top of your head. Researchers can manipulate individual Hox genes and readily see structural differences in the body parts influenced by that gene.

By comparing expression patterns of Hox genes in the fins of skates and closely related sharks, Nakamura is identifying specific genes that may be responsible for the skate’s elongated pectoral fins compared to the shark’s narrower ones. He will then manipulate the expression of these genes in an attempt to alter fin shape.

The blue lines show the cartilage structure in the fins of two fish. Note the shark's narrow fins compared to the skate's wide, fan-like ones. Photo credit: Tetsuya Nakamura, composite image by Laurel Hamers

The blue lines show the cartilage structure in the fins of two fish. Note the shark’s narrow fins compared to the skate’s wide, fan-like ones. Photo credit: Tetsuya Nakamura, composite image by Laurel Hamers

“My opinion is that fin width is very important in deciding fin shape,” he says. “If I can control fin width, for example, to make narrower fin bases in skate, I think their fin shape would be like a shark’s.”

Nakamura, who is spending his first summer at MBL, is a member of Neil Shubin’s lab in the Department of Organismal Biology and Anatomy at UChicago.

A whimsical, enlightening video about cuttlefish camouflage by Jacob Gindi, a senior and biology major at Brown University, appeared in The New York Times last week. Gindi had encountered live cuttlefish when he visited the MBL’s Marine Resources Center as a student in The Art and Science of Visual Perception, a Brown course co-taught by Roger Hanlon of the MBL and Mark Milloff of Rhode Island School of Design. Gindi then had a chance to make a CreatureCast video in Casey Dunn’s Invertebrate Zoology class at Brown. Inspired by Hanlon’s research, Gindi’s artful video about the cuttlefish’s amazingly adaptive skin can be enjoyed by marine biology-lovers of all ages.

“It is so gratifying to see science and art promoted at this national/international scale,” says Hanlon, an MBL senior scientist and professor in Brown’s Ecology and Evolutionary Biology Department through the Brown-MBL Partnership and Graduate Program.

CreatureCast, a collaborative blog produced by members of the Dunn Lab, is supported by a National Science Foundation grant.