Australian Spotted Jelly

Overview

The Australian Spotted Jellyfish (Phyllorhiza punctata) is a large, conspicuous scyphozoan jellyfish native to the tropical western Pacific, ranging from Australia to Southeast Asia. While it thrives in warm, temperate coastal waters, estuaries, and harbors, it has become a widely established invasive species in many parts of the world, including the Americas and the Mediterranean.

Appearance

This species is easily recognized by its rounded, semi-spherical bell, which is typically clear or tinted brown and covered in numerous reflective white spots. It features eight thick, branching oral arms that terminate in cauliflower-like, finger-shaped projections. While most populations host symbiotic algae that provide a brownish hue, some individuals—such as those in the Gulf of Mexico—lack these symbionts and appear clear.

Biology & behavior

Phyllorhiza punctata follows a two-stage life cycle, alternating between a sedentary polyp stage on the seafloor and a free-swimming medusa stage. The medusa stage is diurnal and often aggregates in large swarms, which can significantly impact local ecosystems by consuming vast quantities of zooplankton. These jellyfish possess a mild sting that is generally not considered dangerous to humans. They are sensitive to salinity levels, and low-salinity conditions can cause them to lose their symbiotic algae.

Feeding

As filter feeders, they primarily consume zooplankton. In areas where they have been introduced, their dense aggregations can disrupt food webs by competing with native fish and crustaceans for food, and they are known to ingest significant numbers of fish eggs and larvae.