Friends of Farm Pond, Oak Bluffs, MA
 

Gonionemus vertens: New to the Vineyard

The jellyfish were somewhat unusual in that they had a cross marking against their otherwise clear bell. The jellyfish tended to rest with the upper part of its bell on the bottom of the
sample bottle.
The jellyfish were somewhat unusual in that they had a cross marking against their otherwise clear bell. The jellyfish tended to rest with the upper part of its bell on the bottom of the sample bottle.
During an eelgrass sampling project in late June in Farm Pond, we were stung by small jellyfish that seemed to come up out of the eelgrass blades when we disturbed them. The jellyfish were somewhat unusual in that they had a cross marking against their otherwise clear bell. The jellyfish tended to rest with the upper part of its bell on the bottom of the
sample bottle as shown to the right.

The body of the jellyfish is about the size of a quarter and is marked by a cross, formed by the oral arms on the underside of the bell. In this photo, the blue lines are approximately one-third inch apart. Jellyfish use specialized stinging cells located on their tentacles to capture and immobilize their prey- small fish and zooplankton. When sampling in Major’s Cove, the same jellyfish also stung us. UMass divers working in Menemsha Pond also reported being stung by a jellyfish that looked like this. It is likely that this jellyfish was found during Dave Grunden’s species identification project in Farm Pond during 2006.

In an effort to determine what this new creature might be, specimens were sent to Dr. Allen Collins, a jellyfish specialist at the National Museum of Natural History at the Smithsonian.

Dr. Collins confirmed that the jellyfish is Gonionemus vertens. While it is native to the Pacific coast of the U.S., it has escaped to the East Coast and also in Japan. At this point, it is considered an exotic species, that is, one that is found outside of its normal range. What impact it may have on the ecology of our coastal ponds remains to be seen.
For more information on jellyfish

http://www.dnr.sc.gov/marine/pub/seascience/jellyfi.html

W. Wilcox, Water Resource Planner September 2007

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