Friday, September 19, 2014

Freshwater Jellyfish Sighting


Freshwater jelly fish have again made an appearance in Legend Lake.  They were recently observed by ESD staff in the Blacksmith Lake basin.  They have been previously observed in the Pywaosit basin as well.  The jelly fish scientifically named  Craspedacusta sowerbii are found throughout the world.  Their appearance in a body of water tends to be sporadic and nomadic.  It is theorized they are transported by waterfowl which is why they may show up in a body of water they have never been seen in before.  These organisms are small being around 1 inch in diameter and are translucent and can easily be overlooked when on the water. 

Freshwater jellyfish begin life as a tiny polyp, which lives in colonies attached to underwater vegetation, rocks, or tree stumps, feeding and asexually reproducing during spring and summer. Some of these offspring are the sexually reproducing medusae. Fertilized eggs develop into small ciliated larvae called planula. The planula settle to the bottom, and develop into polyps. However, the majority of jellyfish populations existing in the United States are either all male or all female, so there is no sexual reproduction in those populations. During the cold winter months, polyps contract and become resting bodies, called podocysts. It is believed that podocysts are transported by aquatic plants or animals to other bodies of water. Once conditions become favorable, they develop into polyps again.

Like other jellyfish, freshwater jellyfish sting their prey with nematocysts which inject their prey with toxins.  Due to their extremely small size, freshwater jellyfish are unable to sting humans.  So keep on the lookout next time you are out for a chance to see one of nature’s interesting little organisms.  The best time to see them is on calm days in the middle of the lake.  They will be drifting by a few inches under the surface of the water. 

No comments:

Post a Comment