INVASION OF THE MARTINIQUE ISLAND BY THE PARTHENOGENETIC SNAIL MELANOIDES-TUBERCULATA AND THE SUCCESSION OF MORPHS

In Martinique the freshwater snail Melanoides tuberculata was discover ed for the first time in 1979, Several malacological surveys were carr ied out in 1986, 1990 and 1992 and a rapid colonization of the whole i sland was documented. Three distinct morphs were recognized by their c onchological characteristics. The change of the snail densities and th e frequency of these three morphs showed the decline of one morph foll owing the introduction of the two others. The mechanism of this phenom enon is unknown. However, this displacement is possibly due to competi tion which occurred between morphs although other factors may be invol ved. It was also noted that the colonization of the rivers was often d elayed by natural or artificial barriers.