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.
