Polka-Dotted Nudibranch

Phyllidia polkadotsa

Phyllidia polkadotsa is a nudibranch characterized by its yellow or orange back adorned with large round black spots, each encircled by a paler, translucent ring. This species is primarily found in the Hawaiian Islands and has also been recorded in the Western Central Pacific, including the Philippines and Marshall Islands. Typically, divers encounter this nudibranch at depths shallower than 40 meters, with most sightings occurring around 30 meters or less. It inhabits various benthic environments, often associated with sponge gardens, where it can be found resting on the substrate. Feeding primarily on sponges, this nudibranch plays a role in its ecosystem by contributing to the control of sponge populations. As a simultaneous hermaphrodite, Phyllidia polkadotsa engages in unique mating behaviors, where individuals will dart their penises toward each other to determine which will act as the male and which as the female. After mating, eggs are deposited on the substrate, where they develop into a planktonic larval stage before maturing into adults. Diving encounters with this species can be intriguing, as they often move slowly across the reef, allowing for close observation. Their distinctive coloration and patterns make them relatively easy to identify among other nudibranchs. Conservation status for this species is currently not evaluated, indicating a need for further research into its population dynamics and habitat requirements.