Allow me to introduce you to Ophiojura, a strange deep-sea creature discovered in 2011 by scientists from the French Natural History Museum while trawling the summit of a remote seamount called Banc Durand, 500 meters below the waves and 200 kilometers east of New Caledonia in the southwest Pacific Ocean.
Ophiojura is a type of brittle star. Brittle stars are distant relatives of starfish that have snake-like arms spreading from their bodies and reside on sea floors worldwide. As a specialist on deep-sea species, I immediately recognized this one when I first saw it in 2015. Each arm is ten cm in length and is equipped with rows of hooks and spines. Additionally, the teeth! A microscopic examination revealed bristling rows of razor-sharp teeth lining each jaw, which I believe are employed to capture and shred prey.
As my colleagues and I have now reported in Proceedings of the Royal Society B, Ophiojura is a truly unique and hitherto undescribed species of animal. It is unique — the last surviving member of an old lineage, such as the coelacanth or the tuatara.
We examined DNA from a variety of different marine species and determined that Ophiojura is around 180 million years older than its closest living brittle star relatives. This indicates that their most recent common ancestor lived during the Triassic or early Jurassic periods, when dinosaurs were still in their infancy.
Since then, Ophiojura’s ancestors have continued to evolve, culminating in its current status as the sole known survivor of an evolutionary lineage spanning 180 million years.
Interestingly, we discovered little fossil bones that resemble our new species in Jurassic (180 million-year-old) rocks in northern France, confirming their ancient origins.
Scientists used to refer to animals such as Ophiojura as “living fossils” but this is incorrect. Living beings do not remain unchanged for millions of years. Ophiojura’s ancestors would have continued to evolve, albeit in very modest ways, during the last 180 million years.
Perhaps a more fitting word for these evolutionary outliers is “paleo-endemics” — representatives of a once-vast branch of life that is now confined to a few tiny locations and possibly a single isolated species.
Paleo-endemism is concentrated on continental margins and seamounts in tropical waters between 200 and 1,000 metres deep. This is where we find “relicts” of ancient marine life — creatures that have survived for millions of years in a relatively rudimentary state.
Seamounts, such as the one where Ophiojura was discovered, are often submerged volcanoes formed millions of years ago. Lava oozes or belches from undersea vents, continuously building up layers of basalt rock on the volcano’s crown, much like icing on a cake. The volcano may eventually rise above the sea surface, generating an island volcano similar to those found in Hawaii, occasionally surrounded by coral reefs.
However, the volcano eventually dies, the rock cools, and the seamount sinks into the relatively soft oceanic crust due to the weight of the basalt. With enough time, the seamount will sink hundreds, if not thousands, of metres below sea level and eventually reclaim its habitat for deep-sea animals. Its sunlight past is preserved in rock in the form of a layer of fossilized reef creatures surrounding the peak.
While our new species is native to the southwest Pacific, seamounts are found throughout the planet, and we are only now beginning to investigate those in other oceans. In July and August, I will conduct a 45-day expedition aboard Australia’s oceanographic research vessel, the RV Investigator, to seamounts in the eastern Indian Ocean near the Christmas and Cocos (Keeling) Islands.
These seamounts are extremely ancient – up to 100 million years old – and largely unknown. We are genuinely thrilled about what we may discover.
Seamounts are unique features of the deep sea. Currents whirl around them, bringing nutrients from the depths or trapping plankton from the surface, which supports the growth of beautiful fan corals, sea whips, and glass sponges. These in turn are home to a plethora of other deep-sea creatures. However, these interesting societies are threatened by human activities such as deep-sea trawling and mineral extraction.
Recently, the Australian government established a procedure for the establishment of additional marine parks in the Christmas and Cocos (Keeling) Islands regions. Our expedition will collect the data necessary to maintain these parks in the future.
The government of New Caledonia has also established a marine park in the offshore areas surrounding these islands, which includes the Durand seamount. These marine parks serve as beacons of progress in the global effort to improve ocean environmental stewardship. Who knows what strange and wondrous riches await discovery in the depths. The Dialogue