delware environmental institute

UD professor and alum discover sea nettle jellyfish found in Rehoboth and Chesapeake Bay is actually two species

University of Delaware professor Patrick Gaffney and alumnus Keith Bayha, a research associate with the Smithsonian’s National Museum of Natural History, have determined that a common sea nettle jellyfish is actually two distinct species. The Atlantic sea nettle is one of the most common and well known jellyfish along the U.S. East Coast, especially in the Chesapeake Bay and Rehoboth Bay where they commonly sting swimmers in large numbers. Since it was described nearly 175 years ago, the jellyfish has been assumed to be a single species.

The discovery that is was actually two distinct species, Gaffney said, was made possible by DNA sequencing techniques.

“Before DNA came along, people in museums looked at organisms and counted spines and bristles, measured things, and sorted organisms by their physical characteristics in order to identify species,” Gaffney said. “In the case of this jellyfish, which has been commonly known for centuries, Keith found through DNA sequencing that there were actually two groups.”

Turns out, the ocean-based sea nettle jellyfish is larger and has approximately 40 percent more tentacles (40, as compared to 24) than its bayside counterpart. The ocean sea nettle also has a larger bell, the top portion of the aquatic animal, while the tentacles are shorter than those in the bay nettle species.