Scientists haul 149 brand-new deep-sea species from remote Indian Ocean seamounts

A survey of underwater mountains rising from the floor of the Indian Ocean has turned up 149 species that had never been recorded by science, adding to growing evidence that the deep sea around isolated volcanic seamounts holds far more biodiversity than researchers previously assumed. The expedition catalogued more than a thousand species in total across a stretch of ocean that had never before been the subject of deep-water research.

The survey targeted seamounts near Christmas Island and the Cocos (Keeling) Islands, remote Australian territories southwest of Indonesia, sitting between Australia and Sri Lanka in open water rarely visited by research vessels.

An expedition led by Museums Victoria

The project was led by Tim O’Hara, a marine scientist at Museums Victoria in Melbourne, whose team surveyed depths ranging from about 94 meters down to 5,431 meters, or roughly 308 feet to nearly 18,000 feet. That range spans everything from sunlit shallows to the crushing pressure and near-freezing temperatures of the abyssal plain, giving researchers a rare cross-section of marine life across an entire depth gradient in a single expedition. O’Hara told Mongabay that no previous deep-ocean research had ever been conducted in that particular stretch of the Indian Ocean, calling it “a massive hole in the data” before the survey began.

Seamounts as isolated evolutionary islands

The seamounts themselves are ancient volcanic formations, estimated at 40 million to 120 million years old, some spanning up to 70 kilometers, or about 43 miles, across at their base. Because seamounts rise abruptly from the surrounding abyssal seafloor, they can act like underwater islands, creating isolated habitats where currents concentrate nutrients and where species can evolve in relative isolation from populations on neighboring seamounts or continental slopes. Mongabay reported that the survey mapped a largely unexplored dark seafloor punctuated by dozens of these formations, several of which had never previously been sampled by any research team.

What the 149 new species include

Among the newly described species are a sea cucumber from the genus Oneirophanta, a previously unknown fish belonging to the greeneye family, Chlorophthalmus, and a parasitic barnacle from the genus Rhizolepas that lives attached to other marine organisms. The full results, covering all 1,059 species identified during the expedition, were published in June 2026 in the journal Deep-Sea Research Part II: Topical Studies in Oceanography, according to FishBio. Roughly 14 percent of everything the team collected turned out to be new to science, a strikingly high proportion for a single survey and a sign of how little of the deep Indian Ocean floor has been sampled compared with better-studied basins in the Atlantic and Pacific.

Why seamount surveys matter beyond taxonomy

Cataloguing new species is only part of the value of expeditions like this one. Seamounts are increasingly targeted for deep-sea mining exploration and, in some regions, bottom trawling, both of which can disturb habitats before scientists have had a chance to document what lives there. A comprehensive baseline survey, like the one conducted around Christmas Island and the Cocos Islands, gives conservation planners and regulators a record of biodiversity that can inform decisions about which seamounts might warrant protected status. It also helps researchers understand how species disperse between isolated seamounts separated by hundreds of kilometers of inhospitable, food-poor abyssal plain, a question that remains only partly answered even in well-studied ocean basins.

The expedition also turned up evidence of much older ocean history alongside the living specimens. Sediment samples collected from the same seamount chain contained a dense accumulation of fossilized shark teeth, estimated at roughly 22 million years old, preserved in sea-floor sediment that had gone undisturbed long enough for the teeth to accumulate in unusually large numbers. Finds like that give paleontologists a window into which shark lineages patrolled that part of the Indian Ocean long before the modern seamount ecosystem took shape, and they underscore how little sediment coring has been done in the region compared with the biological trawling and camera surveys that produced the bulk of the 149 new species.

A slow, ongoing process of species description

Formally describing a new species involves far more than collecting a specimen. Researchers must compare each animal against known relatives, often using genetic sequencing alongside physical examination, before publishing a description detailed enough for other scientists to confirm the classification. That process means the 149 species named in this survey likely represent only a portion of what the expedition actually collected, with additional specimens still awaiting full taxonomic review. Museums Victoria’s team has indicated the broader Indian Ocean seamount survey is part of a longer-running effort to map deep-sea biodiversity across the region, suggesting further species descriptions from the same expedition are likely to follow in future publications as additional specimens complete review.

Natural history museums that house expedition specimens, including Museums Victoria’s own collection, generally retain reference material indefinitely once a species has been formally described, since a single preserved specimen can be revisited by other researchers years or even decades later as genetic sequencing techniques and comparative databases continue to improve. That practice is part of why large surveys like this one carry value well beyond their initial publication: unnamed material collected on one expedition sometimes forms the basis for species descriptions published a decade or more afterward, once a taxonomist with the right specialized expertise finally works through the backlog of collected but unstudied animals. Deep-sea groups such as barnacles, sea cucumbers and small fish are especially prone to this kind of delay, since relatively few specialists worldwide are trained to distinguish closely related species within those families.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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