Some animals have made a name for themselves for their reproductive habits. Take seahorses, for example. They form life partnerships, dance together every morning, and the males are the ones that get pregnant. These unusual behavioral patterns, coupled with their aesthetic and emotional appeal to the general public, have made seahorse mating rituals anything but arcane knowledge. Jellyfish reproduction, on the other hand, hasn’t entered the public consciousness in the same way.
Jellyfish reproduction entered my consciousness several months ago when I visited the Monterey Bay Aquarium. The main purpose of my visit was to see an exhibit called The Secret Lives of Seahorses, but what really ended up stealing the show for me was the beauty of the jellyfish display. Entranced, I tried to learn as much as I could about these mysterious creatures. The descriptions the aquarium provided, however, were incomplete; while seahorse mating rituals were described in great detail, I could not find a thing on how jellyfish “did it”.
So, upon returning, I carried out on my own investigation and found this aptly titled special report from the National Science Foundation: “Jellyfish Reproduction: The Holy Grail to Understanding Jellyfish Blooms.” The following is a summary of what I learned.
1) Jellyfish males—yes, there are separate male and female jellyfish—release vast quantities of sperm into the ocean. Jellyfish gonads develop in the lining of the gut; thus, the sperm is released from the mouth. The “magic” happens when the female swims through the cloudy waters. Depending on the species, the females carry their eggs in a brood pouch or in their stomach, so fertilization occurs in one of these locations.
2) Fertilized eggs develop and hatch (through the mouth, of course) into a swarm of free-swimming jellyfish larvae called planula.
3) Planula attach themselves to hard surfaces, like rocks or shipwrecks. Once affixed, they mutate into flower-like polyps, which multiply and stack together like LEGO blocks. Scientists think that these polyps can lay dormant for years and even decades while waiting to bud.
4) When the environmental conditions are just right, polyps bud and release baby jellyfish. Typically, tens of thousands of jellyfish are released into a small portion of the ocean at once, which offers them the best chance of survival.
5) In just a few short weeks, jellyfish are mature and ready to start the next reproduction cycle.
6) Jellyfish die after a few months. Life is short, but sweet. Rest in peace, little jellyfish.