Turritopsis dohrnii, commonly known as the “immortal jellyfish,” is a small, translucent marine invertebrate known for its remarkable biological trait. This hydrozoan possesses the unique ability to undergo transdifferentiation, a process where its adult cells revert to an earlier, sexually immature polyp stage when faced with stress or injury. By effectively restarting its life cycle, this tiny creature is considered biologically immortal in theory, though it is still vulnerable to predation and disease in the wild. Because its complex life cycle includes both free-swimming and stationary forms, its diet and feeding strategy change dramatically depending on its stage of development.
Primary Food Sources
The adult, free-swimming medusa form is a carnivore that preys upon small organisms suspended in the water column. Its diet consists entirely of tiny marine life, making it an opportunistic consumer in the planktonic community. The primary components of its meals are various forms of zooplankton, which include microscopic animals and the larval stages of larger crustaceans and mollusks.
The medusa also consumes the eggs and newly hatched larvae of many fish species, intercepting them as they drift through the open ocean. This preference for suspended organic matter means the jellyfish feeds on whatever is abundant in its immediate surroundings. Because the adult form is small, typically reaching a maximum bell diameter of only about 4.5 millimeters, its prey must also be minuscule.
Small mollusks and copepods, which are tiny crustaceans, represent a significant energy source for the adult jellyfish. The medusa actively targets zooplankton (animal components) rather than relying heavily on plant-like phytoplankton for sustenance. The food it captures provides the necessary energy to fuel its active, although passive, movements through the water.
Habitat and Feeding Strategy
The medusa stage of Turritopsis dohrnii is found globally, inhabiting temperate to tropical waters. This wide distribution, likely facilitated by human shipping, ensures a constant supply of diverse planktonic prey. The jellyfish is entirely dependent on the currents and the density of local food sources, as it does not actively pursue prey over long distances.
The tiny medusa captures its food using a ring of numerous, filamentous tentacles that trail from the edge of its bell. These tentacles are lined with specialized stinging cells called nematocysts, which inject a paralyzing venom into any prey that brushes against them. Once immobilized, the tentacles contract to guide the captured organism toward the central opening, which serves as both its mouth and its anus.
In addition to the passive drift method, the medusa employs a more active technique involving its bell structure. It can quickly expand its bell, creating negative pressure that draws water and nearby prey closer to its tentacles. This movement, which also helps propel the jellyfish, ensures the efficient capture of small, slow-moving targets. All food is ingested and waste is expelled through the single opening, and digestion occurs rapidly to maintain buoyancy.
Dietary Needs of the Juvenile Stage
The life of the immortal jellyfish begins as a planula, a small, free-swimming larva that eventually settles on a hard surface to form a sessile colony of polyps. This polyp stage, often called a hydroid, is fixed to the substrate and has a fundamentally different method of acquiring nutrition compared to the adult medusa. The polyps are stationary filter-feeders, often found attached to rocks, the seafloor, or man-made structures like floating docks.
These polyps extend small tentacles to passively filter micro-organisms and fine detritus from the surrounding water column. The diet at this stage primarily consists of microscopic organic particles and bacteria that settle near the ocean floor. By remaining attached, the polyp colony exploits the constant flow of nutrients carried by the currents.
The colonial nature of the hydroid means that the resources collected by one polyp contribute to the growth and eventual asexual budding of new, genetically identical medusae. The sessile polyp is sustained by a continuous, low-energy intake of minute particles, which prepares the colony to release the actively feeding medusa into the ocean.