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   Euglandina rosea (mollusc) français     
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         General Impact

    Molluscs are the group most affected by extinction according to the 2007 International Union for Conservation of Nature (IUCN) Red List (Regnier 2009). The Pacific region has a wide diversity of mollusc species, most of them unique to the region, and the majority endemic to single islands or archipelagos (Cowie 1996 1997a, in Cowie and Cook 2001). More and more, these unique species are becoming replaced with a homogenous group of tropical tramp snail and slug species that are increasingly widespread (Cowie 1998a, R.H. Cowie, unpub., in Cowie and Cook 2001). Of the 400 extinct species we listed from oceanic islands, 234 lived on islands to which Euglandina rosea had been introduced, and it is highly probable that of these 234 extinctions, 134 (>50%) of them were ultimately caused by the introduction of E. rosea (Regnier et al. 2009).

    E. rosea contributed to the extinctions of endemic Partula tree snails in French Polynesia; the snails are widely distributed on most of the high islands of the tropical Pacific, except for the Hawaiian Islands (Murray et al. 1989, Cowie 1992, Hopper and Smith 1992, in Cowie and Cook 2001). E. rosea also contributed to the marked decline of endemic land snail fauna in Hawaii and Mauritius (Murry et al. 1988; Clarke et al. 1984; Hadfield 1986, Murray et al. 1988, Griffiths et al. 1993, Wells 1995, in Satoshi 2003). The best documented cases are those of the achatinelline tree snails, which are endemic to the Hawaiian Islands (Hadfield 1986, Hadfield et al. 1993). The native species mentioned seem especially vulnerable to heightened levels of predation because of their extremely slow rate of reproduction (Cowie 1992; Hadfield et al. 1993, in Cowie and Cook 2001).

    The carnivorous snail was introduced to control numbers of the giant African land snail (Achatina fulica) (Nishida and Napompeth 1975, in Cowie 2000). However, no rigorous scientific evidence exists that E. rosea controls A. fulica (Christensen 1984, in Cowie 2000) and, as a consequence, the World Conservation Union (IUCN) has formally condemned the deliberate introduction of E. rosea and other carnivorous snails. Most governments and other authorities appear to be aware of the potential threat posed to native fauna by E. rosea, however, under pressure to do something about A. fulica, they may misguidedly consider the introduction of E. rosea (and other species such as the flatworm Platydemus manokwari).

    Disease transmission: E. rosea was found experimentally to be able to serve as both an intermediate and a paratenic host of Angiostrongylus cantonensis.




         Location Specific Impacts:
    Tutuila Is. (American Samoa) English 
    Threat to endangered species: On Tutuila Samoana abbreviata (previously considered probably extinct) is an extremely rare species (15 snails seen), Samoana conica is more common (288 snails) but still rare and Eua zebrina is the most common (1102 snails at one locality perhaps near its natural abundance) (Cowie and Cook 2001).
    Bermuda English 
    Predation: Euglandina rosea preys on native snail species (Varnham 2006).
    Society Islands (French Polynesia) English 
    Predation: The loss of most species of Partula in the wild (Lee et al. 2008) on the Society Islands other than Tahiti occurred due to the introduction of Euglandina rosea. On Tahiti the mixed species populations in the Te Pari area of Tahiti-Iti are still extant, but the predatory snail E. rosea has now spread to the last valley on the Peninsula that did not have previous evidence of predator activity. On Tahiti-Nui populations of partulid, without the predator, were found near the crest of Mount Tahiti above Orofero Valley.
    Huahine Is. (French Polynesia) English 
    Economic/Livelihoods: On Huahine the disappearance of the critically endangered Partula varia and Partula rosea (due to predation by E. rosea), had an economic and social effect on the local community. The shells were used for making lei (shell jewellery) and many of the women of the villages lost their livelihoods.
    Moorea Is. (French Polynesia) English 
    Predation: Partula spp. of Moorea have for more than a century provided a natural laboratory for the study of variation, genetic polymorphism and speciation. As a result of the introduction of E. rosea, all the species of Partula from Moorea are now believed to be extinct in the wild. Since E. rosea is spreading rapidly on Tahiti, the demise of Partula on that island also is imminent (Murray et al 1988).
    Raiatea Is. (French Polynesia) English 
    Reduction in native biodiversity: The greatest single loss of Society Island tree snail diversity occurred on Raiatea, French Polynesia (Coote & Loeve 2003).
    Tahiti Is. (French Polynesia) English 
    Predation: Partula spp. of Moorea have for more than a century provided a natural laboratory for the study of variation, genetic polymorphism and speciation. As a result of the introduction of E. rosea, all the species of Partula from Moorea are now believed to be extinct in the wild. Since E. rosea is spreading rapidly on Tahiti, the demise of Partula on that island also is imminent (Murray et al 1988).
    Guam English 
    Predation: Not only was Euglandina rosea introduced, but an extremely voracious predatory flatworm, Platydemus manokwari, was also introduced and has contributed to the decline of partulids on that island (Hopper & Smith 1992, in Cowie & Cook 2001).
    Chichi-jima Is. (Japan) English 
    Reduction in native biodiversity: In 1995, Mandarina mandarina was extinct in one of the northern areas of Chichijima Island. There were already Euglandina rosea (Kurozumi 1988, in Ohbayashi et al. 2007) and several predatory flatworms (but not P. manokwari) in this area (Kawakatsu et al. 1999), so these predators affected M. mandarina in the 1980s, and subsequently in the 1990s, the invasion of P. manokwari might have been the final blow for M. mandarina.
    Bonin Islands (Ogasawara-gunto) (Japan) English 
    Predation: Mandarina snail species have suffered serious destruction of habitat due to cultivating land for crops since 100 years ago (Kurozumi 1988; Tomiyama 1994 in Satoshi 2003). However, the most serious problem is predation by introduced species. For example, the predatory flatworm, Platydemus manokwari, other predatory flatworms and the carnivorous land snail E. rosea (Kawakatsu et al. 1999, Ohkouchi et al. 1999, Tomiyama 2002, in Satoshi 2003). The effect of these introduced predators on native land snail fauna is so serious that they may rapidly cause the extinction of many of the native land snails in the Ogasawaras.
    Mauritius English 
    Predation: Most prey of Euglandina rosea are eaten whole. Achatina spp., which Euglandina was originally introduced to control, was not positively identified in the diet. Even if all unidentified prey fragments were from Achatina then this would form less than 5% of the total number of items in the stomachs. Habitat destruction, together with predation by Euglandina, appear to be major contributors to the extinctions of native Mauritian snails (Griffiths Cook & Wells 1993).
    Hawaii (United States (USA)) English 
    Predation: Achatinellaines are poorly adapted to predation pressure and are unable to cope with Euglandina rosea (Hadfield 1986, Hadfield and Miller 1989, in Howarth 1991). Disease or unknown mortality factors may also have been important (Hadfield 1986 in Howarth 1991).

    Reduction in native biodiversity: Non-target impacts of Euglandina rosea included the consumption of native snails (Hoddle 2004). The best documented cases of native snail reduction in Hawaii due to E. rosea are those of the achatinelline tree snails, which are endemic to the Hawaiian Islands (Hadfield 1986; Hadfield et al. 1993, in Cowie and Cook 2001). The complete extermination of a well-studied population of the endemic Oahu tree snail Achatinella mustelina corresponded with the arrival and increase of E. rosea in the study site (Hadfield and Mountain 1981, in Howarth 1991). Most of the 41 recognised species of Achatinella are extinct, and the remaining populations are officially listed as endangered under the United States Endangered Species Act. E. rosea even enters shallow water to prey on aquatic snails and has been implicated in the decimation of the native Hawaiian lymnaeid snails (Kinzie in prep, in Howarth 1991).



ISSG Landcare Research NBII IUCN University of Auckland