Moon jellyfish live in the Atlantic, Pacific and Arctic Oceans near the coastline. In most cases, they are harmless to humans. Yet their same tentacles containing the stinging cells that trap prey and defend the jellyfish from predators may inadvertently hit humans resulting in skin irritation.
Two Life Stages
Jellyfish have two life stages: one in which they are sexually active and the other in which they reproduce asexually. The sexual phase -- when the jellyfish is matured -- is called the Medusa phase referencing the fact that the tentacles and arms hanging from its clear-colored and bell-shaped body resemble the snakes protruding from the head of the Gorgon Medusa in Greek mythology as per Answers In Genesis. The polyp phase -- the asexual stage -- of a jellyfish's life begins when as a fertilized egg it is released from its mature mother. Polyp float freely in the ocean for an indefinite period of time and then attach to a shaded area such as a rock. Mystic Aquarium tells us that polyp then make carbon copies of themselves that are released in the water.
Sexual maturity for moon jellyfish occurs in spring and summer. It is easy to spot a sexually mature or adult moon jellyfish, it has four horseshoe-shaped gonads located near the bottom of its stomach that are visible through its clear-colored and bell-shaped body. These gonads are nourished immediately by prey taken in by the adult moon jellyfish often taking on a violet or pink color.
When jellyfish do reproduce sexually, its successful completion is literally dependent on the direction of ocean currents. Male jellyfish detect the flow of the ocean's currents and position their bodies so that as they release a string of sperm from their mouths the sperms flow toward the mouths of females. Once the eggs are fertilized, they cling to the mother's arms and develop until released.
How Long They Live
The answer to how long a jellyfish lives depends on which phase of life it is in. Polyps have lived up to 25 years in an aquarium setting. Mature moon jellyfish that are producing sexually do not live long past the start of their active status. Sex for a jellyfish is a signal to die. After this critter has done its part sexually to ensure the survival of the species, its clear body become opaque, loses its buoyancy and the dying creature falls to the ocean floor.
Amy M. Armstrong is a former community news journalist with more than 15 years of experience writing features and covering school districts. She has received more than 40 awards for excellence in journalism and photography. She holds a Bachelor of Arts in communications from Washington State University. Armstrong grew up on a dairy farm in western Washington and wrote agricultural news while in college.