Freshwater jellyfish

Craspedacusta sowerbii · Aquatic life

Whole animal · Photo: Павлик Лисицын / CC BY

IntroducedFreshwater jellyfish or hydra

Also called Craspedacusta sowerbyi, Peach blossom jellyfish, Craspedacusta

How to identify Freshwater jellyfish

Clear to whitish bell about the size of a dime to a quarter (up to about 1 inch)
Fringe of many fine tentacles around the edge of the bell
Four whitish cross shaped bands visible inside the bell
Pulse up and down through the water, often in groups

Similar species

Nothing else in local ponds looks quite like it. Floating clumps of zooplankton or clear Volvox balls are much smaller and do not pulse.

Profile

Season	Jellyfish appear in late summer and early fall; most of the year it lives as tiny, unnoticed polyps on the bottom.
Starts	Medusae show up in warm water, usually above about 75 F
Depth	Open water, often near the surface on calm days
How it spreads or reproduces	Tiny polyps and resting stages moved with plants, fish stocking and equipment
Habitat	Warm, calm ponds, lakes, reservoirs and old quarry or gravel pits.

Why it matters in a lake

Native to China and now found worldwide, appearing unpredictably one year and not the next. Its stings are too weak to bother people, and it does no known harm to fish.