Pocillopora damicornis

Lore & Background

Pocillopora damicornis is a colonial coral that can grow into clumps up to 30 cm high. It is distinguishable from other members of the genus by the verrucae (wart-like growths) on its surface being more irregularly arranged, and it is more branched than the otherwise similar P. verrucosa. Its form varies according to habitat: more open and branched in calm positions, more compact on upper parts of reefs where water movement is greater. Its colour varies and may be greenish, pink, yellowish-brown or pale brown.

This coral is native to the tropical and subtropical parts of the Indian and Pacific Oceans, with a wide range extending from East Africa and the Red Sea to Japan, Indonesia, Australia, Hawaii, Easter Island, and the western coast of Central America. It is found at depths to about 40 m, but is most common between 5 and 20 m, often forming dense patches. It is equally found on reef slopes and in lagoons, among mangroves and on wharves, but not in areas with strong water movement.

P. damicornis is a reef-building coral, grows fast, and is a strong competitor. The polyps extend their tentacles at night to feed on plankton. It reproduces both asexually by fragmentation and sexually as a simultaneous hermaphrodite. In most of its range it broods planular larvae, but in Western Australia it both broods larvae and releases gametes by broadcast spawning, while in the Eastern Pacific only broadcast spawning takes place. It contains microscopic symbiotic dinoflagellate algae (zooxanthellae) within its tissues, and compared to other corals, this species is resistant to bleaching.

Reader's Guide

Pocillopora damicornis is significant as a reef-building coral that grows fast and is a strong competitor, contributing to the structural complexity of coral reefs across the Indian and Pacific Oceans. Its wide distribution—from East Africa and the Red Sea to Japan, Indonesia, Australia, Hawaii, Easter Island, and the western coast of Central America—makes it one of the most abundant corals. The species is notable for its high interaction rate with symbiotic dinoflagellates: according to the GeoSymbio Database, it interacts with 30 species (or subclade types) of Symbiodinium, the highest rate of any known coral species along with Stylophora pistillata. This symbiosis is dynamic, with algal density varying with seasonal changes in water temperature, light levels, and dissolved nitrate concentration; extreme conditions can cause bleaching, but the species is relatively resistant. Its reproductive versatility—including fragmentation, brooding, and broadcast spawning depending on region—contributes to its resilience and dispersal ability, with larvae remaining viable for up to 100 days. Despite its abundance and resilience, the IUCN has listed it as endangered, as it is susceptible to reef degradation, and it is collected for the aquarium trade and mined for cement in some regions. Like all corals, it is listed on CITES Appendix II.

A Fossil in a Young Archipelago

Pocillopora damicornis appears in the documented Cenozoic fossil record of Hawaii, a distinction that carries particular weight given the geological youth of the islands. The oldest Hawaiian island is barely more than five million years old, and the Paleobiology Database records no known occurrences of Precambrian, Paleozoic, or Mesozoic fossils anywhere in the state. This means every prehistoric life-form whose fossilized remains have been reported from within Hawaii falls squarely within the Cenozoic window, spanning from 66 million to 10,000 years ago. For a coral species like P. damicornis, its presence in this catalogue signals that its lineage, or a closely comparable form, was already contributing to the marine ecosystems that shaped these volcanic islands. The dagger symbol preceding the name in the fossil list marks it as an extinct or no longer extant form in the Hawaiian context, distinguishing it from living species that may still occupy similar ecological niches in the archipelago's waters today.

Among the Pocillopora Clan

Within the Hawaiian Cenozoic fossil catalogue, Pocillopora damicornis is not a solitary entry. It shares its genus listing with four other species: P. eydouxi, P. ligulata, P. molekensis, and P. verrucosa, all similarly marked with the extinction dagger. This clustering suggests the Pocillopora genus as a whole left a meaningful trace in the archipelago's geological past. The broader coral representation in the same list is equally striking. Genera such as Acropora, Fungia, Porites, Pavona, Montipora, Leptastrea, Cyphastrea, and Gardineroseris all appear alongside P. damicornis, painting a picture of a diverse stony-coral community that once thrived in Hawaiian waters. Some entries carry notes of uncertainty, such as the phrase 'or unidentified comparable form,' acknowledging the interpretive challenges paleontologists face when working with fragmentary remains. The co-occurrence of so many coral genera in one fossil inventory underscores that these were not isolated occurrences but part of a structured reef ecosystem.

A Window into a Vanished Reef Community

The Cenozoic life list for Hawaii reads less like a single-species profile and more like a census of an entire vanished marine world. Pocillopora damicornis sits alphabetically among hundreds of entries spanning mollusks such as Conus, Mitra, Lyncina, Oliva, Drupa, and Charonia; bivalves including Arca, Chama, and Ostrea; gastropods like Nerita and Turritella; and even a handful of bird species including Branta, Circus, Corvus, and Pterodroma. Several of these bird entries are flagged as type localities, meaning Hawaii is where the species was first formally described from fossil material. The sheer breadth of the assemblage, corals, sponges, echinoderms, and vertebrates compressed into one alphabetical index, reveals that the Cenozoic Hawaiian environment supported a complex, multi-trophic community. P. damicornis, as a branching coral, would have formed the structural backbone of that community, providing habitat for the very mollusks and invertebrates catalogued alongside it.

The Limits of a Five-Million-Year Archive

What makes the Hawaiian fossil record, and by extension the placement of Pocillopora damicornis within it, so constrained is the simple fact of the islands' age. At just over five million years for the oldest island, Hawaii has no geological strata reaching back into the Mesozoic, Paleozoic, or Precambrian eras. The Paleobiology Database confirms zero known occurrences of fossils from those deeper time periods within the state. This means the entire prehistoric narrative available to researchers is compressed into the Cenozoic, a window stretching from 66 million to 10,000 years. For a species like P. damicornis, this implies any fossil evidence of its presence in Hawaiian waters must be relatively recent in geological terms. There is no deep-time baseline to compare against, no older reef strata to show how the coral community evolved across hundreds of millions of years. The fossil record here is a snapshot rather than a film reel, and every entry, dagger-marked or not, represents a narrow slice of a story that could not have been told any earlier.