Coral & Invertebrates

Learn & Explore/Species/Coral & Invertebrates

Discover corals and other invertebrates found in Hawai‘i

What Are Invertebrates?

Invertebrates are animals that do not have a backbone or spine. There are many marine invertebrates that live in our ocean, including corals, octopus, sea urchins, and more! Read on to learn more about common invertebrates you can find in Hawai‘i.

Coral

What Are Corals

Corals are actually a bunch of tiny animals living together called polyps. Inside the polyps live tiny microscopic algae called zooxanthellae.
Polyps and zooxanthellae have a mutualistic symbiotic relationship, where the zooxanthellae provide energy to the coral through photosynthesis, and in return the coral polyp provides protection and nutrients.
Coral polyps live together in groups and secrete a hard, calcium carbonate skeleton, building the colorful reefs you see in the ocean.
In the Kumulipo, the Hawaiian creation chant, the coral polyp was one of the first living creatures created — all other sea animals and fish came afterward. This shows just how important corals are.

Why Corals Are Fragile

While corals have a hard skeleton, it is still very fragile and can easily break through physical contact.
Only a thin layer of tissue covers the surface of corals — this delicate layer can easily be damaged through minor physical contact such as a light touch or accidentally brushing against it, leaving the coral vulnerable to infection.
Corals are also suffering from climate change, pollution, and other human impacts.

Visit the Coral Reefs page to learn more about threats to corals, why they matter, and how you can help protect our reefs.

Common Hawaiian Corals

Cauliflower Coral

Pocillopora meandrina

This coral is found at depths to about 150 feet. Commonly called Cauliflower coral, the colonies form cauliflower-shaped heads about 10 to 20 inches in diameter. Branches are heavy and leaf-like, and fork bluntly near the ends. All branches have wart-like projections called verrucae that are covered with calices. Color of living colonies ranges from brown to pink.

Antler Coral

Pocillopora grandis

Colonies consist of thick branches that resemble moose antlers, with broad or cylindrical tips. This species also possesses verrucae and is usually found in depths of 35 to 150 feet. Antler corals can grow to at least 4 feet in height or diameter. Live colonies are brown in color and usually darker than other Pocilloporid corals.

Finger Coral

Porites compressa

Distinguishing features are the finger-like branching and shallow snowflake-shaped calices. This species is most common in wave-protected areas like bays or deeper reef slopes to depths of about 150 feet. It has many growth forms, but all of them show some sort of fingerlike branching. Color of live colonies ranges from light brown to light yellowish-green.

Lace Coral

Pocillopora damicornis

This delicate and fragile coral forms small bushy clumps up to about 6 inches in diameter. Colonies consist of fine branches covered with calices. These branches range from long and slender in calm waters to more robust forms in areas with wave action. Sometimes the skeleton will create pocket formations around a crab that lives among the branches. Usually found on inner portions of large reef flats, this species appears to strongly depend on sunlight, as it is rarely found below about 30 feet. Colonies range in color from light brown in shallow waters to dark brown in deeper waters.

Lobe Coral

Porites lobata

Lobe corals produce encrusting and sometimes massive forms on the reef from the intertidal zone to depths of over 180 feet. Long narrow cracks found on the coral heads are produced by a type of alpheid shrimp. Calices have a snowflake-like appearance and are shallow and flush to the surface. Living colonies range in color from yellowish-green to brown.

Rice Coral

Montipora capitata

The most obvious characteristic of this coral is the tiny, white bumps or projections (papillae) that cover the surface, which makes it look like rice. These papillae are smooth with no calices on them. Calices are found on the surface of the coral between the papillae. This species is found at depths up to about 150 feet. It has a number of growth forms ranging from platelike to branchlike and encrusting types. Color of living colonies is usually brown. If the colony is growing in a plate form, the edges may be white.

Other Invertebrates

Day Octopus or He‘e

Octopus cyanea

This is the most common octopus found in Hawai‘i during the day, as other species of octopus usually hunt at night. They feed on smaller crabs, shrimp, sometimes fish, and other molluscs, and have amazing camouflage abilities that allow them to not only change colors but also the texture of their skin! The Day octopus’ arms can grow up to 3 feet long, but only live up to about a year.

Limpet or ‘Opihi

Cellana species

The 3 most common species of ‘opihi in Hawai‘i are Makaiauli (Cellana exarata), ‘Ālinalina (C. sandwicensis), and Kō‘ele (C. talcosa). Makaiauli are usually found in the upper splash or spray zones to mid-intertidal areas, ‘ālinalina in the middle to lower intertidal zones, and kō‘ele, the largest species, live mostly on subtidal boulders submerged underwater. ‘Opihi is a traditional, popular food source considered to be a delicacy by some, but their populations are currently in decline due to habitat loss and overharvesting. They can be eaten raw or boiled, and are often described as tasting like oysters or abalone but more firm, crunchy, and rich.

Helmet Urchin or Hā‘uke‘uke

Colobocentrotus atratus

The helmet urchin’s unique shape helps make it more resistant to strong waves and are mainly found along wave-impacted intertidal shorelines. They can grow to about 3 inches in diameter, and have modified spines on top that look like shingles with very strong tube feet that enable them to cling to rocks without being washed away. Native Hawaiians used hā‘uke‘uke for medicine, and some also like to eat their gonads as a delicacy.

White-Spotted Sea Cucumber or Loli

Actinopyga varians

Sea cucumbers are detritivores, meaning they feed on dead or decomposing organic materials found in sediment. After ingesting sediment from the bottom of the ocean floor and filtering out the organic matter, they excrete the leftover sand back out through their cloaca or anus. Sea cucumbers are unique in that they also breathe through their cloaca, and the White-Spotted sea cucumber even has teeth surrounding its anus!