Johnston Atoll, Pacific

Octocorals represent a highly diverse group of colonial organisms distinguished by numerous polyps with eight (‘octo’) hollow tentacles. These deep and cold water octocorals feed on particular particles drifting through the water. To optimise this feeding mechanism, most octocorals extend upwards into the water, adopting various forms such as fans, brushes or whips. They often service as habitats for other marine life including brittle stars, lobsters and worms. Octocorals sampled in this expedition include soft corals, sea pens, bamboo corals and primnoids.

Also known as antipatharians, black corals are a type of soft coral found in deep waters. Their name derives from their uniquely coloured skeletons, which have been used for centuries to make jewelery. While they inhabit all oceans, they are most common in the deep waters of tropical and subtropical regions, like those explored during this expedition. Black corals can be a defining feature of deep water reef systems.

Sponges are filter feeding invertebrates, among the earliest animal groups in evolutionary history. In many deep-sea regions, they form the primary species, creating intricate and diverse ecosystems. The expedition sampled sponges like the glass sponges (Hexactellinida), recognised by their silica spicule skeleton that can merge into complex designs.

Predominantly deep-sea dwellers, squat lobsters boast long claws, often extending twice their body length. They sometimes associate with other marine species, including octocorals. Contrary to their name, they share a closer genetic link to hermit crabs.