Posted: Jan. 25, 2012, 2:30 p.m. EST
By John Dawes
A few months ago, Spanish authorities issued a nationwide ban on the circulation, sale, breeding and ownership of apple snails. This decision was taken as a result of a plague of apple snails, centered mainly around the delta of the River Ebro, which is wreaking havoc on the region’s extensive rice fields. The aim of the measure was to prevent the spread of this invasive snail to other parts of the country.
Consequently, all apple snail imports from third countries were prohibited, and a strict rule was imposed requiring all aquatic plants from such countries to be examined and certified free of the snail. Other measures included the legal requirement for all rice-harvesting machinery used in the Ebro region to be certified as having been cleaned after use.
Not surprisingly, these drastic steps caused great concern within the Spanish ornamental aquatic sector, since one species of apple snail, the spiketop apple snail (Pomacea bridgesii) is regularly imported and sold throughout the country, and is known not to have either the voracious appetite or invasive potential of P. canaliculata, the South American or channeled apple snail. Indeed, P. bridgesii is deemed not to present any threat to macrophytes (aquatic plants that are large enough to be visible to the naked eye), including rice, which grows in flooded paddy fields.
It has now been clarified by the Spanish authorities that the prohibition extends to just two species: P. canaliculata and P. insularum. P. bridgesii is therefore exempt. However, this was definitely not the impression created when the prohibition was first announced by the Ministry of the Environment, Rural and Marine Affairs (Ministerio de Medio Ambiente y Medio Rural y Marino-MARM).
|Two smallP. bridgesii(wild-type coloration) showing the 90 degrees between the bottom whorl and the one next to it (see text for further details).|
Photo by John Dawes
For the moment, the Spanish trade is breathing a little bit easier. But, is this the calm before a new storm? Other Member States of the European Union are also taking a look at controlling (or prohibiting?) importation and sale of apple snails.
It is hoped within the industry that no draconian steps are taken and due care is given to identifying the species before banning orders are issued.
Admittedly, accurate identification is not particularly easy for those who are not familiar with these snails. However, there is one feature that can be used to differentiate between P. canaliculata and the different color forms of P. bridgesii: the angle formed between the top edge of the largest whorl and the bottom of the next whorl. In P. canaliculata, this angle is acute, i.e., less than 90 degrees, while in P. bridgesii it is 90 degrees, i.e., a right angle (see accompanying photo of a couple of young P. bridgesii that shows this right angle clearly).<HOME>
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