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Wednesday, Oct. 22, 2008
Golden apple snail
By ROWAN HOOPER
Japanese name: Sukumiringogai
Scientific name: Pomacea canaliculata
Description: A fairly large snail with a shell 40 to 60 mm wide and 45 to 75 mm high, and coloration varying from yellow and green to dark brown; some have spiral bands. The tentacle-like antennae are hidden under the shell at rest.
Where to find them: Originally, in Argentina, from where they spread to other parts of South America, then to the southern United States. They were introduced to Taiwan in the 1980s with the idea of farming the mollusk for food, and they spread from there, colonizing Southeast Asia, then southern China and Japan. Now they are found in waters from Honshu to Kyushu and Okinawa.
Food: Plants; this snail's voracious appetite makes it ill-suited for aquariums, and it is seen as an invasive pest in some areas.
Special features: Amphibious animals, Golden apple snails (like other snails in this family) are unusual in having both lungs and gills. The body is divided to accommodate both forms of breathing apparatus, with the gills on the right side and a lung on the left. The snails spend daylight hours underwater, breathing through their gills, emerging onto land and switching to air-breathing at night while searching for plants to feed on. Their activity rate depends on temperature, but they are fairly tolerant of cold weather. The operculum — the "door" of the shell — is tight-fitting, protecting them from dehydration. If the oxygen content of water is low, the snails can extend a breathing siphon out of the water like a snorkel, and draw in air through it. There is no distinct reproductive season, but egg-laying increases the warmer it gets. Golden apple snails become sexually mature when they reach 2.5 cm in size, and females lay between 200 and 600 bright-orange eggs.
PHOTO COURTESY OF BIO-IMAGE NET