365 Urban Species. #189: Moon Jelly

[urbpan]

Photo by cottonmanifesto. Location: Castle Island beach.

Urban species #189: Moon jelly Aurelia aurita

Tourists in Boston, visiting the area around the New England Aquarium, look into the harbor and see the local wildlife. "There's another one!" Water filthy with drink bottles and discarded snack wrappers laps against the paved wharves of the city, while round and translucent animals drift to the surface and then back down into the murk. Moon jellies are found worldwide at the coasts. They are predators, catching small animals like larval crustaceans and mollusks in their short stinging tentacles and layer of mucus on their undersides. Certain kinds of pollution--fertilizer, sewage--increase the number of moon jellies in the water, making them generally more numerous around human activity. They also may become seasonally very common, at times some shallow waters may be thick with them. Often they are stranded on beaches, drying to a thin disc of sand stuck together with protein. They are fed upon by sea turtles, who have been known to die eating floating plastic bags mistaken for jellyfish.

Four semicircular markings in the moon jelly show the location of the sex and digestive organs. Color in these markings can indicate what food the jellies are eating (pinks and oranges for shrimp, for example). Accompanied by a local reporter, wandering the city to look at wildlife, we discovered that some of the moon jellies had three markings, and many had six. The significance of this variability remains a mystery to me.



Many moon jellies, stranded on Castle Island beach.






Moon jellies in Boston Harbor, outside the Aquarium. (originally posted last year)


Captive moon jellies on exhibit inside the New England Aquarium.

Comments

[by-steph.livejournal.com]

I think the food capture by the mucus method takes place on the surface of the bell, rather than the "undersides". It might be also interesting to point out that the mouth is also the anus. Disambiguation with ctenophores ("snot pets" or "comb jellies") that have the brilliant advancement of a mouth separate from the anus might also be interesting. Both tend to wash up as little gelatinous mounds. People tend to be afraid of both, but moon jellies don't usually cause a sting for most people and ctenophores don't sting.

[urbpan.livejournal.com]

Thanks for that (the first sentence especially). My references were unclear. I have seen wild comb jellies, but at Cape Cod, not in the city. I wish I understood deuterostomes and other -stomes better, and where cnidarians fit in all that; but my job is to bridge the gap between scientists and laypeople, and most laypeople don't want to know about jellyfish anuses. But that doesn't mean I shouldn't understand them.

[by-steph.livejournal.com]

"Most laypeople don't want to know about jellyfish anuses"

I find that very hard to believe.