Rare land snail filmed laying an egg
A Department of Conservation ranger caring for a population of Powelliphanta augusta snails in Hokitika has for the first time caught a snail laying an egg on video.
In the video, a small egg, resembling a tiny hen's egg, emerges from the neck of the unique land snail.
Doc has been managing a captive population of the threatened snails in chilled containers in Hokitika since 2006, when State-owned mining company Solid Energy started mining the snail habitat on the Mt Augustus ridgeline on the western side of the Stockton Plateau, near Westport.
Doc ranger Lisa Flanagan, who filmed the egg being laid, has been looking after the snails in Hokitika for more than 12 years. She said working with the snails was not the kind of job she ever imagined herself doing, but it was constantly providing surprises.
"It's remarkable that in all the time we've spent caring for the snails, this is the first time we've seen one lay an egg. We caught the action when we were weighing the snail. We turned it over to be weighed and saw the egg just starting to emerge from the snail."
Doc senior science adviser Kath Walker said having a hard shell in which to retreat from predators and dry conditions was a great strategy for the snails but brought some problems too — how to get sperm from your mate into your shell and any resultant eggs out.
" Powelliphanta have solved this by having an opening (a genital pore) on the right side of their body just below their head so that the snail only needs to peek out of its shell to do the business.
"It extends its penis out of this pore and into its mate's pore, and its mate does the same, simultaneously exchanging sperm, which they can store until they each fertilise the sperm they have received to create eggs.
"As hermaphrodites, they have both male and female genitalia, so although they usually mate with another to cross fertilise their eggs, as carnivores which have to live at relatively low density, being able to occasionally self-fertilise must help with survival of the species."
The captive management of Powelliphanta augusta snails has saved these animals from extinction and enabled scientists to learn more about the lives of these incredible creatures, which are only found in New Zealand.
Very little was known about the snails when they were taken into captivity, and we are discovering new things all the time, Ms Flanagan said.
" Powelliphanta augusta are slow growing and long lived, not being sexually mature until they are about 8 years old and then laying only around five big eggs annually which can take more than a year to hatch. Some of our captive snails are between 25 and 30 years old — in this they're polar opposites to the pest garden snail we introduced to New Zealand which is like a weed, with thousands of offspring each year and a short life."
Doc has established new populations of the snail in the wild and reintroduced them into new and rehabilitated habitat.
— Greymouth Star
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