Corals and Other Invertebrates Archives | Oceana

Pacific Purple Sea Urchin

Urchins on the Pacific seafloor, including purple sea urchins, are important prey for sea otters and sea stars. Pacific purple sea urchins are also eaten by humans. The meat inside, known as “uni” in Japanese,2 is considered a sushi delicacy, and the demand for this delicacy has been growing in recent years. Pacific purple sea urchins … Read more

Christmas Tree Worm

Christmas Tree Worms are named for their spindly, fir tree like appearance. Their festive looking crowns protrude from their otherwise tube-like body, composed of radioles (similar to hair) appendages radiating from the worm’s spines.  Christmas Tree Worms are ciliary feeders, which means they use cilia, tiny-hair-like bristles on their appendages, to catch food as it … Read more

Fried Egg Jellyfish

This jellyfish spends a lot of time motionless, slowly pulsing its bell while drifting. The numerous short, club-like appendages extending from it contain mouth-arm openings through which the jellyfish traps prey and feeds.1 The primary prey of the Fried Egg Jellyfish is zooplankton and other jellyfish. These appendages are usually colored a deep purple and while … Read more


The bluebottle, or Indo-Pacific Man o’ War, is not a jellyfish but a siphonophore, which is a colony of tiny, specialized polyps working together as colonies. The bluebottle is easily recognized by its blue, gas-filled sac (pneumatophore) that floats on the water’s surface. During summer in the Southern Hemisphere, strong winds carry bluebottles to the … Read more

Blue Glaucus

The blue glaucus, which is also called the blue dragon, sea swallow, or blue angel, is a brightly colored nudibranch, commonly known as sea slugs.  Found throughout the Atlantic, Pacific, and Indian Oceans in tropical and subtropical waters, the blue glaucus grows up to 1.2 inches (3 cm) long. These tiny sea slugs spend most … Read more

Lion’s Mane Jellyfish

The lion’s mane jellyfish cannot be missed in the open ocean where it prefers to float about. With tentacles up to 120 feet long, some individuals even rival in size the blue whale, the largest animal in the world. Most lion’s mane jellyfish live in the Arctic and North Pacific Ocean from Alaska to Washington … Read more

Portuguese Man o’ War

The Portuguese man o’ war is a highly venomous open ocean predator that superficially resembles a jellyfish but is actually a siphonophore. Each man o’ war is actually a colony of several small individual organisms that each have a specialized job and are so closely intertwined that they cannot survive alone. In this manner, the … Read more


The bright orange, white-tipped structures along the flameback’s dorsal surface are called cerata and increase the surface area of the skin. This nudibranch absorbs oxygen through its skin, so increased surface area aids in respiration. The cerata also increase the number of defense cells that the flameback can store from its prey. The flameback, like all nudibranchs, is … Read more

Felimare Cantabrica

Felimare cantabrica, like all nudibranchs, is simultaneously hermaphroditic – each individual produces both eggs and sperm. An individual cannot fertilize its own eggs, however, and pairs still must mate. They reproduce via internal fertilization and lay eggs, which they stick to the reef surface or other hard substrates. The long strings of eggs are often spiral shaped. Neither parent … Read more

Chilean Basket Star

The Chilean basket star is a species of brittle star that lives in the dee fjords of southern Chile and perhaps in other deep benthic habitats of southern South America. This species, like all basket stars, has five-part symmetry, with all of the hair-like appendages originating from five central arms that repeatedly divide into the … Read more