In the rainforests of Papua New Guinea, where arboreal tree kangaroos, vibrant birds-of-paradise and ornate birdwings hog the limelight with their charismatic presence, teeny-tiny, leaf litter-eating land snails don’t always stand a chance to vie for scientific attention. Although land snail shells hold an essential place in PNG’s culture — as jewelry and adornments in ceremonial clothing — scientific understanding of these mollusks is, at best, patchy.

Worldwide, more 30,000 land snail species are known to science. While species in North America and Europe are relatively well-studied, those in forested tropical regions, such as the Amazon and Congo basins and islands like New Guinea, have been barely sampled. “Any land snails from Papua New Guinea, or for that matter most species of plants and animals, whatever we know is based on colonial times to a large extent,” said malacologist Frank Köhler at the Australian Museum, who studies land snails in Australia and the Pacific Islands.

The lack of current scientific knowledge on Papua New Guinea’s land snails inspired malacologist John Slapcinsky at the Florida Museum of Natural History in the U.S. to begin an eight-years-long survey in the country — the first such endeavour after six decades and, in Slapcinsky’s words, one of the most intensive surveys in the country’s history. In a new study published in the journal Archiv für Molluskenkunde, Slapcinsky and his colleagues report the discovery of nine new species of land snails from the country.

 

Between 2002 and 2010, the researchers hiked through rainforests and mountain peaks in PNG, laboriously sieved through leaf litter at more than 200 sites and collected nearly 20,000 specimens. They compared these with existing museum collections to identify previously unknown snails, identifying nine new species.

The newly described land snails are about the size of a fingernail and have tightly coiled, lens-shaped, whitish-brown shells. “They are very attractive little snails,” said Slapcinsky. “A lot of them have sharp ridges on them, which also makes the shell visually interesting.”

Although little is known about their diets, rows of dagger-like teeth suggest they are carnivores. Like most land snails, they are hermaphrodites, having both male and female sexual organs. They aren’t widespread and are found only on an island or a mountain.

“Snails have an important role as part of the recycling of nutrients in rainforests as they are feeding mostly on decaying plant matter, fungi and microorganisms,” said Köhler, who was not involved in the research. “This study is interesting in that the snails that the researchers studied are very elusive and very inconspicuous species that are also not very abundant.”

Bulisa Iova, curator of biodiversity collections at the PNG National Museum and Art Gallery, welcomed the news of this discovery. “This is very good for science and for the country because we now know that we have nine new species of snails added to the list of species that have been described before,” he said in an email to Mongabay. While Iova is familiar with Slapcinsky’s work, he was not involved in the study.

Attractive, elusive little snails

The researchers have grouped all newly discovered snails under the existing genus Torresiropa. “If we knew more about them, there might be multiple genera involved, but I don’t have enough data to be able to do that,” explained Slapcinsky, “And I don’t want to just make up genera that are later going to be synonymous.”

The most visually striking of the nine is T. aurilineata, found in the gravelly soil of rainforests in the eastern Papuan Peninsula and named after the gold-toned bands on its shell. The frisbee-shaped T. paterivolans, collected from leaf litter in the Rossel Island rainforests, is the largest among the nine snails, with shells reaching about 13 mm (0.5 inches) wide. It is named after the Latin word for flying saucer.

Other new species from the country’s islands include T. krausi from Sudest Island, named after the herpetologist Fred Kraus, whom Slapcinsky accompanied during his trips to PNG; the plant-climbing T. muyuaensis from Woodlark Island (also known as Muyua); and T. nusaensis found on a fallen coconut frond in Nusa Island.

In the cloud forests of Emua Peak on Mount Riu, the researchers found T. oreas, named after a mountain nymph Oreas. The small-shelled T. pinsina, named after an adjective meaning “small portion” in the Mengan language, was found in the leaf litter in New Britain.

Shells collected by citizen scientists also contributed to the identification of two species. T. worsfoldi, from Manus Island (also home to the impressive Manus green tree snail), and T. cresswellorum from Bougainville Island were named after the collectors. In addition to describing new species, the researchers redescribed T. spaldingi, whose morphology hadn’t been entirely known, and moved the species Rhytida bednalli to the genus Torresiropa.

Despite conducting an extensive survey, the researchers say they could not sample many hard-to-access areas in PNG where roads don’t exist. Among the land snail specimens the researchers sampled, only 31% were previously known to science, raising hopes for more discoveries. “This is just the tip of an iceberg,” said Köhler. “A single study discovering a number of new species in a very elusive group just shows you that there would be so much more to discover.”

However, the ongoing forest losses in PNG threaten land snails, some of which are yet to be discovered. “They are a group that’s had a very high rate of extinction,” said Slapcinsky. Since 1500, around half of recorded extinctions have been land snails, many from the Pacific Islands. “We don’t know when [they went extinct], we don’t know what they did, we don’t know anything about them.” He hopes to avoid that fate with land snails in PNG by documenting them before they are gone.

“I think our main concern now is the loss of habitats,” said Iova. “It’s definitely a huge threat to the loss of biodiversity.”

Banner image: Torresiropa paterivolans, Rossel Island, Papua New Guinea held by John Slapcinsky, courtesy of Jeff Gage for the Florida Museum of Natural History.

Citation:

• Slapcinsky, J., & Murphy, A. E. (2023). Overlooked predatory snails from Papua New Guinea: nine new Torresiropa Solem, 1959 (Gastropoda: Stylommatophora: Rhytididae). Archiv Für Molluskenkunde, 152(2), 135–152. org/10.1127/arch.moll/152/135-152

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