The white-spotted jellyfish (Phyllorhiza punctata) is a large marine organism recognized by its translucent, often light-brown, hemispherical bell covered with numerous small white spots. This jellyfish typically averages 45 to 50 centimeters in bell diameter, though some individuals reach up to 74 centimeters in introduced ranges. Native to the warm, coastal waters of the Indo-West Pacific (Australia to Japan), it has established widespread populations in non-native areas, including the Gulf of Mexico, the Caribbean, and the Mediterranean Sea. This article explores the specific diet and feeding mechanisms that allow this jellyfish to thrive and become an invasive presence in new ecosystems.
Specific Food Sources
The diet of the white-spotted jellyfish consists almost entirely of tiny organisms suspended in the water column, collectively known as zooplankton. These jellyfish are highly effective filter feeders, continuously straining microscopic prey from the seawater. Their primary food items include small crustaceans like copepods, which are a major energy source in marine food webs. They also consume the early life stages of various marine animals, including the eggs and larvae of fish, shrimp, and bivalves. A single large adult jellyfish can filter up to 50,000 liters of seawater per day, allowing them to sustain their large size even when food densities are relatively low.
Environmental conditions influence the feeding requirements of P. punctata. Some native populations harbor symbiotic algae, called zooxanthellae, which contribute energy through photosynthesis. In contrast, populations in the Gulf of Mexico often lack these symbionts, making them entirely dependent on capturing planktonic prey for all their nutritional needs. A successful bloom of these jellyfish is often a direct indicator of high zooplankton productivity in the surrounding water.
How They Capture Prey
Phyllorhiza punctata employs a continuous filter-feeding strategy that relies on its physical structure and swimming motion. The jellyfish possesses eight thick, highly branched oral arms that hang beneath its bell, forming a dense, cauliflower-like mass. These oral arms act as a complex, three-dimensional filtration system. The rhythmic contractions of the bell serve the dual purpose of locomotion and generating a steady current of water. During the bell’s relaxation phase, water is drawn into the sub-umbrella space and channeled over the specialized surfaces of the oral arms.
This constant flow allows the jellyfish to efficiently process vast quantities of water as it swims slowly. Prey particles are trapped on the oral arms, which are covered in a sticky layer of mucus, sometimes referred to as a “mucus net.” Small stinging cells called nematocysts line these arms and help to subdue the tiny, trapped zooplankton. Once captured, the small prey items are transported along the oral arms to clusters of minute, polyp-like mouthlets, where they are ingested and passed into the digestive system.
Ecological Consequences of Their Diet
The massive consumption rates of the white-spotted jellyfish have significant consequences for the marine ecosystems it inhabits, particularly where it is an invasive species. Their voracious appetite for zooplankton directly reduces the food available for native filter feeders, such as small fish, shrimp, and other invertebrates. When the jellyfish aggregate in dense swarms, they rapidly deplete the local supply of copepods and other micro-zooplankton, effectively outcompeting native species. This resource depletion creates a negative cascading effect through the food web, known as a trophic cascade, indirectly affecting species at higher trophic levels.
The consumption of fish eggs and larvae reduces the number of young fish that can grow to maturity, leading to a decline in commercial fish populations. The impact is especially pronounced in coastal areas and estuaries, where the jellyfish aggregate and where many commercially valuable fish and shellfish species reproduce. By feeding heavily on the early life stages of shrimp, crab, and finfish, P. punctata poses a direct threat to the recruitment success of these species. The ecological outcome is an altered food web structure, where the jellyfish becomes a dominant consumer.