Land Planarians of the family Geoplanidae (Flatworms) are simple animals; they have a rudimentary nervous system, lack a through gut (so that they must regurgitate any waste products), and have no respiratory organs (they absorb oxygen through their moist, non-watertight skins, but cannot actively collect it, meaning they can never dry out and cannot grow very large). Nevertheless they can be voracious predators of other invertebrates, and can be very harmful when they are introduced to ecosystems where the local invertebrate fauna is unfamiliar with them. This is particularly true on small islands where invertebrate faunas are often highly endemic, and low in numbers; such populations can be quickly overwhelmed by exotic predators.
In a paper published in the journal Zookeys on 4 June 2012 a team of scientists led by Karin Breugelmans of the Royal Belgian Institute of Natural Sciences discuss the discovery of some exotic blue Flatworms from an orchard at Ciutadella de Menorca on the easternmost Balearic island of Menorca, and the implications of that discovery.
Map showing the location of Menorca. Breugelmans et al. (2012).
Breuglemans et al. carried out DNA analysis of the worms in order to find out their species and determine that they were invaders, and not a previously undescribed part of the local fauna. This revealed the worms to be members of the species Caenoplana coerulea, a highly invasive Flatworm native to eastern Australia, which has previously been introduced to New Zealand, the United States, the United Kingdom, Norfolk Island, France, and Argentina and mainland Spain. This species has proved particularly problematic in North America; it was first recorded in California in 1943 and had reached Florida by 1961.
Caenoplana coerulea from Menorca. Breugelmans et al. (2012).
The first specimens of Caenoplana coerulea were collected from the orchard in 2009. In 2011 it was also found in a nearby garden. The likely impact of Caenoplana coerulea on the invertebrate fauna of Menorca is hard to assess, but in other places it has proved very hard to eradicate once established due to its broad diet; it will predate a variety of invertebrate groups including earthworms, snails, insects, isopods and millipedes.
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