Moon jellyfish, scientifically known as Aurelia aurita, are common and captivating marine animals found across the world’s oceans. These translucent creatures are easily recognized by their distinctive moon-like bell, which can range from 10 to 35 centimeters in diameter, and the four horseshoe-shaped gonads visible through their bell. Often encountered in coastal waters, harbors, and inlets, they sometimes wash ashore after strong currents. Their simple yet elegant appearance belies a fascinating biology.
How Long Do Moon Jellyfish Live?
The lifespan of a moon jellyfish in its adult, or medusa, stage ranges from 6 to 12 months in the wild. Most individuals live between 8 and 12 months, though some may survive for up to two years under optimal conditions. However, many wild moon jellyfish do not live beyond six months due to various environmental challenges.
In controlled environments like aquariums, where conditions are stable and food is readily available, moon jellyfish can live longer, often 12 to 24 months. This extended longevity in captivity highlights the impact of external factors on their survival.
What Affects Their Lifespan?
Several environmental factors significantly influence the lifespan of moon jellyfish in their natural habitats. Water temperature plays a role, with warmer waters supporting faster growth and reproduction. Food availability also directly impacts their survival, as sufficient prey is necessary for proper development and energy. When food is abundant, the survival rate of young jellyfish (ephyrae) and their development can improve.
Water quality, including dissolved oxygen levels and pollution, is another influential factor. Moon jellyfish exhibit a notable tolerance to low dissolved oxygen concentrations, which can give them an advantage over other marine species in certain areas. Conversely, pollutants like plastic waste and chemical contaminants can negatively affect their health and reproductive capabilities.
Predation also acts as a natural control on their populations. Sea turtles, various fish, and birds are known predators, with high mortality during the ephyra stage from filter-feeding organisms like mussels.
The Journey of a Moon Jellyfish: Life Cycle Explained
The life cycle of a moon jellyfish is a complex process involving both sexual and asexual reproduction. It begins with the adult medusa, where males release sperm into the water, and females ingest it to fertilize their eggs.
These fertilized eggs develop into free-swimming larvae known as planulae, which are covered in hair-like cilia. After a period of drifting, the planula larva settles onto a solid surface, such as a rock or the seafloor.
Here, it transforms into a sessile polyp, also known as a scyphistoma, an attached, anemone-like stage. This polyp stage can persist for many years, acting as a long-term reservoir for the species. The polyp can reproduce asexually by budding off new, genetically identical polyps, creating a colony. When environmental conditions are right, often triggered by changes in temperature, the polyp undergoes a process called strobilation. During strobilation, the polyp elongates and develops horizontal constrictions, resembling a stack of tiny disks. Each of these disks then detaches from the polyp, becoming a free-swimming, immature jellyfish called an ephyra. These ephyrae continue to grow and develop, eventually maturing into adult medusae, completing the cycle.