NZ females get their revenge overseas

Completely fed up with the devastation wrought on our ecology by the introduction of gorse, ferrets, stoats, rabbits, myrtle rust, PSA, Mycoplasma bovis and so on and so forth; New Zealand females have sallied forth to wreak revenge on other countries all around the globe.

Having discovered, in true feminist style, that males are utterly superfluous, these females have perfected the technique of completely overrunning a habitat, driving out the locals, consuming all the food and reproducing in extraordinary numbers.

This reverse colonisation began in Ireland?around 1837, then England in?1859, spreading across Europe; Germany, Poland,?Western Baltic Sea area, Russia,??Azov Black Sea region, Ukraine,?Catalonia, Mediterranean region of France,?Italy,?Turkey,?Czech Republic,?Slovakia, and Greece, since November 2007

In 1987 the USA was targeted and they are spreading rapidly, multiplying to amazing densities in their newly adopted locations all across the nation.

The New Zealand mudsnail is a tiny aquatic snail that inhabits lakes,?rivers, streams, reservoirs and estuaries. In addition to mud, the snail can also be found lurking?on rock or gravel surfaces, aquatic vegetation, or woody debris. New Zealand mudsnails are?highly adaptable to diverse climates and can tolerate a broad range of aquatic conditions such?as temperature, salinity, turbidity, water velocity, and stream productivity. In the United?States, New Zealand mudsnail populations are comprised almost entirely of self?cloning?parthenogenetic females (no need for fertilization here). The brood size of an individual female?ranges from 20?120 embryos, each of which may mature to produce an average of 230?offspring per year, so a?single female mudsnail can result in a colony of 40 million snails in one year.

The high reproductive potential of New Zealand mudsnail enables it to reach extraordinary?densities in some locations. Researchers at Montana State University have reported densities of up to 750,000 snails per square meter in Yellowstone National Park. Large colonies of New?Zealand mudsnails can comprise up to 95 percent of the total macroinvertebrate biomass, and consume up to half of the available food in a stream. New Zealand mudsnail may outcompete?or displace native snails, mussels, and aquatic insects which native fish species depend on for food. This disruption to the food chain may ultimately result in reduced growth rates and lower?populations of economically important fish species.

The highest concentration of New Zealand mudsnails ever reported was in Lake Zurich, Switzerland, where the species colonized the entire lake within seven years to a density of 800,000 per m?.

This miniscule menace is?only about 4 ? 6 mm in length as an adult. The snails shell?is light to dark brown, with five to six whorls or spirals. The opening?of the shell has a retractable cover called an operculum which allows?the snail to seal itself inside when it feels threatened or is exposed to?pollutants. The mudsnail?s ability to completely seal its shell allows the snail to survive out of water for several weeks in cool, damp conditions.

Some fish and birds feed on New Zealand mudsnail, but?the rigid operculum and thick shell wall enable many snail to pass?through the digestive system of predators unharmed.??They hold no nutritional?value for native fish species so tend to get left alone.

The only other NZ animal species to have set off on an OE and made a nuisance of itself (apart from the Kiwis on the annual London pub crawl) is the New Zealand flatworm, an invasive species in Europe where it preys on earthworms and degrades soil quality.

This has been another public educational service brought to you by Whaleoil.? We thought you would like to know.