Amazing translucent bodies pulsating in the sea, with tentacles of varying length, complexity and stinging potential trailing behind them. These are one of the most beautiful, and sometimes deadly, creatures of the sea—the moon jellyfish. Ascending from a late afternoon dive off the Andaman Islands, I found myself surrounded by thousands of moon jellyfish near the surface. Though they are more or less harmless to human beings, welts do appear on the skin of individuals who have an allergic reaction to them, especially around the neck and face. But their stinging nematocysts rarely penetrate human skin and aren’t much of a bother. I have had many encounters with these creatures and I am comfortable swimming through the crowd I meet at the surface. Time seems to shift during the dance of the jellyfish, and I find myself mesmerized every time I swim through a colony of them. As I am surrounded, their fragile, translucent bells saturate the water in every direction. Soft, angled sunlight shines through their pale pink bodies as they move rhythmically.
Several species of jellyfish frequent India’s oceans, with moon jellyfish one of the most common among them. It belongs to the genus Aurelia, a group that has at least 13 species found throughout the world. Their colour varies from white to light pink, and they are recognizable by the four circular gonads easily visible through the top of the bell of the animal. They thrive during the warmer months of April and May, when the water temperature is high and the dissolved oxygen content is low.
Aurelia jellyfish feed on plankton floating in the water, as well as larval crustaceans, molluscs, fish, fish eggs, and other small organisms. The tentacles have stinging nematocysts to capture prey as well as deter predators. Tiny hair-like cilia move the captured prey from the tentacles to the bell of the jellyfish, and then to its gastrovascular cavity.
Moon jellyfish show a high tolerance to low oxygen in the water. During the warmer months, as other species move away from oxygen-depleted areas, moon jellies congregate in large numbers and thrive. These jellyfish are eaten by a variety of predators that include fish and turtles. Their natural life span is about six months in the wild. Warmer waters, daily reproduction, and low levels of food leave them susceptible to disease and infections. It is not uncommon, therefore, to see ragged individuals closer to the reef occasionally being nibbled at by reef fish.
Moon jellyfish are at their majestic best when observed from underneath, with the sunlight streaming through their bells. They seem to move to the beat of a slow, silent drummer that only they can hear. There is something poetic about the way they float in the ocean, and I never tire of watching them, or attempting to capture their intricacy through my lens.
SPOT THEM:
Moon jellyfish can be seen in all the seas around India, from Goa and Lakshadweep to the Gulf of Mannar and the Andaman and Nicobar Islands.
About the author
