From hornshark to 'Dumbo' octopus, CSIRO's RV Investigator keeps revealing new Australian species
Australia’s oceans continue to yield a steady stream of previously unknown life, and the CSIRO research vessel RV Investigator is at the heart of the discoveries. Marine ecologist Dr Ben Arthur, a Voyage Manager with the CSIRO Marine National Facility, reflected on standout finds and on what happens between spotting an unusual specimen and its official recognition by science.
The haul spans scales and depths: from microscopic algae skimming the East Australian Current to sharks and octopuses cruising the deep. Among the smallest is Greyjoyella mundugala, a tiny, shrimp-like crustacean announced at the end of 2025 and collected about four kilometres beneath the ocean surface.
Just 2.5 millimetres long, it belongs to a group abundant in deep-sea sediments. Its genus name nods to the Greyjoy family of Game of Thrones, while the species name honours Mundugala, a spirit from Australian Indigenous mythology. At the other end of the spectrum is the Painted Hornshark (Heterodontus marshallae), the largest new species so far described from RV Investigator voyages.
Reaching about 600 millimetres, the deep-sea shark is related to the Port Jackson Shark and was long mistaken for a close relative until researchers from the Australian National Fish Collection helped identify, describe and reclassify it. Deep-sea life can also be unexpectedly endearing.
O’Loughlin’s Sea Cucumber (Deima oloughlini) is oval, soft-bodied and bristling with appendages—10 pairs of legs and 20 tentacles along its roughly 110-millimetre body. It filters sediments for food and helps recycle nutrients that keep the seafloor healthy. Not all discoveries come from the depths or are visible to the naked eye.
Pseudo-nitzschia hallegraeffii, a diatom around 55 micrometres long, was collected at the ocean surface during a 2016 voyage in the East Australian Current and formally described in 2018. The species was named for University of Tasmania professor Gustaaf Hallegraeff in recognition of his work on harmful algal blooms.
Near the surface, Australia’s reefs and offshore seamounts continue to deliver surprises. The Orange-tailed Coralfish (Coradion calendula), a butterflyfish that reaches about 158 millimetres, takes its name from its marigold-like colouring—calendula refers to the flower genus—and occurs in coastal waters around northern Australia.
Few announcements captured public imagination like the Carnarvon Flapjack Octopus (Opisthoteuthis carnarvonensis), unveiled in 2024. Small enough to fit in the palm of a hand, it swims using little flapping fins and can flatten itself like a pancake to hide on the seafloor—traits that lend the group its Dumbo- and flapjack-inspired common names.
Sometimes the most remarkable finds are unplanned. During the 2017 Sampling the Abyss voyage led by Museums Victoria, researchers trawled up a whale skull and bones—and found within them a new species of bone-eating worm living in the remains.
From microscopic algae to deep-sea sharks, the specimens collected with RV Investigator are a window into the immense hidden biodiversity of Australia’s oceans, Dr Arthur said—a reminder of how much remains to be discovered and described.