The three new species of nautiluses belong to the genus Nautilus and represent populations on the easternmost edge of the overall habitat range of the genus.
Underwater photos of Nautilus samoaensis (A and B), Nautilus vanuatuensis (C), and Nautilus vitiensis (D). Image credit: Barord et al., doi: 10.3897/zookeys.1143.84427.
Nautiluses are a charismatic group of marine mollusks best known for their rich fossil record.
But today they are restricted to a handful of species in two genera (Nautilus and Allonautilus) of the cephalopod family Nautilidae.
The three ‘universally’ accepted modern Nautilus species of 21st century taxonomists are Nautilus pompilius (type species), Nautilus macromphalus, and Nautilus stenomphalus.
Nautiluses first appeared 500 million years ago during the Cambrian explosion and are distant cousins of squid and cuttlefish.
These creatures are described as ‘living fossils’ because they have remained virtually unchanged for millions of years.
They occur in the tropical waters of Pacific and Indian oceans, near the coast of Japan, Fiji, New Caledonia and Australia.
Nautiluses have a shell diameter 10 and 25 cm across and more than 90 tentacles — the most of any cephalopod.
Unlike those of other cephalopods, their tentacles have grooves and ridges instead of suckers. These grooves and ridges are coated with a sticky secretion that help the animals grip food and pass it to their mouth. They use their sharp, beaklike mouth to break food apart, and their radula (a band of tissue lined with tiny teeth) to further shred their food.
Nautiluses swim using jet propulsion, expelling water from their mantle cavity through a siphon located near their head. By adjusting the direction of the siphon, they can swim forward, backward or sideways.
To avoid predators by day, nautiluses linger along deep reef slopes as deep as 700 m. At night, they migrate up to shallower depths of about 70 m to feed and lay their eggs.
While most cephalopods are fairly short lived, a nautilus may live for more than 20 years, reaching maturity in 12 to 15 years. The female lays relatively few eggs — between 10 and 18 per year. Her eggs take about 12 months to hatch.
“The populations of nautiluses within American Samoa, Fiji, and Vanuatu have already been effectively isolated from each other because of warm, surface seawater temperatures, depth implosion limits below 800 m, and their nektobenthic lifestyle, one of endless foraging just above the bottom, and thus within a few meters of the benthic environment at most,” said Des Moines marine biologist Gregory Barord and colleagues.
“We combined morphological characteristics with previously published population genomic results to newly describe each population of Nautilus within these archipelagos as a unique species.”
“The characters that showed the most differentiation between the species included multiple color pattern traits (i.e., percent of shell pigmented in matures specimens and striping patterns) and, while not yet quantified, the actual ‘hue’ of pigment in freshly caught specimens.”
The three new species, Nautilus vitiensis, Nautilus samoaensis, and Nautilus vanuatuensis represent populations of nautiluses on the easternmost edge of the overall habitat range of Nautilus.
Nautilus vitiensis inhabits areas along the coast of Viti Levu, Fiji at Suva Harbour and Pacific Harbour.
Nautilus samoaensis inhabits areas near Pago Pago, American Samoa.
Nautilus vanuatuensis inhabits sites within Mele Bay, Vanuatu.
“The designation of these three populations as distinct species provides insight into evolutionary radiation of the genus and clarification for future conservation practices,” the researchers said.
“The fact that we were able to combine the morphology and genetics to differentiate these species provides a foundation for managers and other officials to begin to efficiently identify distinct species of nautilus shells that may come through as trade products.”
Their paper was published in the journal ZooKeys.
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G.J. Barord et al. 2023. Three new species of Nautilus Linnaeus, 1758 (Mollusca, Cephalopoda) from the Coral Sea and South Pacific. ZooKeys 1143: 51-69; doi: 10.3897/zookeys.1143.84427
