One of the world’s most notoriously slow creatures, the
land snail, may soon get a boost in the race against extinction,
thanks to a suite of specimens from the University’s
zoological collection.

Ryan Nowak
Professor John Birch shows his snail shells yesterday. He collected the specimens on the island of Tahiti and neighboring Moorea. Only five species of the snail remain alive in the wild. (JORDAN STECKLOFF/Daily)

Tahitian land snails, famous among the biological community as
examples of species that evolved rapidly in isolated island
environments, now teeter at the brink of extinction. Of 61 species
that once left trails of slime in the leafy forests of the French
Polynesian islands, only about five remain in the wild. An
estimated 15 more have been conserved and bred in zoos, including
the Detroit Zoological Institute.

Zoology Prof. Diarmaid Ó Foighil said he believes he can
aid conservation efforts using samples that have lain unused in a
museum freezer for more than 30 years. The samples, freeze-dried
specimens of original snail populations, were collected by zoology
Prof. John Burch in the early 1970s, before the snails disappeared.
Ó Foighil said genetic information from the samples will
help zoos decide where to repopulate captive populations.

Why should such effort go into saving a handful of different
species of snail?

For Andy Snider who is in charge of the zoo’s collection
of the Detroit Zoo’s more than 500 Tahitian snails, the
answer is many-sided. “Every animal has a reason for being
there in the ecosystem,” he said. Snails serve an important
function as decomposers of plant matter on the forest floor he
explained, releasing nutrients into the ecosystem.

“For all we know,” he added, “that particular
snail might have a micro-parasite in its blood … that could
become a cure for something down the line, or the snail could have
been a food item for something else that’s now not able to
feed as readily.”

Shortly after Burch’s expedition, the Tahitian snails fell
prey to a predatory snail introduced to the French Polynesian
islands in 1975 to control an agricultural pest — itself a
large snail introduced from Africa. Unfortunately, Burch said, the
predatory snail did not control the pest, preferring to prey on
native snail populations.

“This has been cited widely as really bad attempt,
misguided attempt, at biological control,” Burch said.
Although Burch never used his samples and became involved in other
research, he mentioned them in a chance conversation with Ó
Foighil this year.

Ó Foighil realized he could analyze the samples to
understand the snails’ evolutionary relationships. Although
many of the snails are extinct, information about their biology is
encoded in genetic material preserved in the frozen specimens.

Because different snails species may look similar in their shell
characteristics, Ó Foighil explained, current
classifications of Tahitian snails are likely inaccurate. The
preserved samples will permit him to determine exactly which
species belong on which island, he said.

“Right now, our estimate of diversity is guesswork really,
based on appearance,” Ó Foighil said. “With gene
sequences, we can be exact.”

Zoos involved in conservation efforts can compare the genealogy
of captive snail populations with the frozen specimens to help
decide where to repopulate the snails and on which snails to focus
conservation efforts.

“It’s very expensive to keep these things alive in
zoos, and there are limited resources. You have to make these
critical decisions about what you’re going to save and
why,” Ó Foighil said.

Before the predatory snails were introduced in French Polynesia,
Burch visited the head of agriculture of French Polynesia to
explain that the predatory snail would not control the pest and
would likely decimate local snail populations.

“He was totally unreceptive to any advice that I
had,” Burch said. “He told me that biological control
worked, that they were going to do it, and anyway, which were more
important, people or snails?”

Although Burch’s efforts failed to prevent the
snails’ extinction, his samples now represent an unmatched
archive of material.

“Because (Burch) got those samples and preserved them, we
can do research here that no one else on the planet can, because
those populations are now vanished,” Ó Foighil said.
“It’s a really good example of the basic utility of
museum collections.”

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