Platydemus manokwari, de Beauchamp, 1963 de Beauchamp, 1962

Justine, Jean-Lou, Gastineau, Romain & Winsor, Leigh, 2024, Land flatworms (Tricladida: Geoplanidae) in France and French overseas territories: ten years of research, Zoologia (e 24004) 41, pp. 1-25 : 2-3

Platydemus manokwari

Platydemus manokwari ( Figs 1, 2 ) was widely known from its invasion of the Pacific islands ( Gerlach et al. 2021, Winsor 1983). Because the species is a predator of molluscs, it was deliberately established on various islands to counter another invasion, that of the giant snail Lissachatina fulica (Férussac, 1821) . We found Pl. manokwari in only one place in mainland France, a greenhouse in the Jardin des Plantes in the city of Caen ( Justine et al. 2014b). When we published this article in 2014, we considered it possible that the species was spreading in the wild since it had been reported at high altitudes in New Guinea ( de Beauchamp 1972, Winsor 1990), at temperatures comparable to those of continental Europe. Ten years later, we can confirm that Pl. manokwari has never been found in the wild in mainland France. Nonetheless, thanks to international collaborations, in 2015 we mentioned the presence of the species in new localities, including the first report in continental North America, in Florida ( Justine et al. 2015). As of 2023, the species has now largely invaded Florida and even neighboring states in the United States. The species has recently invaded the French Antilles, including the islands of Guadeloupe, Martinique, and Saint Martin ( Justine et al. 2021) and we often (2023) receive citizen science reports on its continued presence on these islands. Its presence has also been recorded on many islands in the Pacific, including Wallis and Futuna, and on several islands in French Polynesia ( Gerlach et al. 2021).

We also studied the genetic structure of Pl. manokwari using specimens from different localities around the world ( Justine et al. 2015). We have not examined specimens from Papua New Guinea, its place of origin (or, at least, its type locality), but we have had specimens from the relatively nearby Solomon Islands. By studying the cox1 gene, we showed that there are two populations. Both are present on the Solomon Islands, therefore close to the species’ place of origin. One of the populations only invaded Australia, while the other population invaded all other localities ( Justine et al. 2015).

The complete mitogenome has been published for Pl. manokwari (Gastineau et al. 2020) , the first species for which we observed an unusual length of the cox2 gene, subsequently confirmed in other Rhynchodeminae (see later paragraph on long cox2).

Figures

Figures 1–2. Platydemus manokwari: (1) Specimen alive collected in a hothouse, Caen, France, dorsal view. (2) Experimental predation on indigenous snail. The prey is the helicid Eobania vermiculata, a common snail of the Mediterranean region. Photos by Pierre Gros, from Justine et al. (2014b).