Platydemus manokwari

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Platydemus manokwari
Platydemus manokwari, head with eyes on top right. Ogasawara Islands, Japan

Platydemus manokwari , head with eyes on top right. Ogasawara Islands, Japan

Systematics
Trunk : Flatworms (Plathelminthes)
Class : Vortex worms (Turbellaria)
Order : Tricladida
Family : Land planarians (Geoplanidae)
Genre : Platydemus
Type : Platydemus manokwari
Scientific name
Platydemus manokwari
de Beauchamp , 1963

Platydemus Manokwari is the land planarians scoring (Geoplanidae) Strudelwurm , originally in Guinea native and, in particular, but from different small animals of snails fed. It has been introduced into many areas by humans, where it has beenlinkedas an invasive species with the decline of snail populations up to the extinction of species.

features

Top and bottom of Platydemus manokwari
Head of Platydemus manokwari with eyes

The flatworm becomes about 40 mm to 65 mm long, 4 mm to 7 mm wide and less than 2 mm thick. Both ends of the worm are pointed, but the head, which has two dark eyes, is more pointed than the end of the tail. The top of the body is dark brown with a lighter central longitudinal line, the underside is a solid pale gray.

Life cycle

Like all vortex worms, Platydemus manokwari is a hermaphrodite , whereby the animals fertilize each other . About 4 days after copulation, they lay down about 2 mm to 5 mm large, translucent egg capsules that contain 3 to 9, on average 5 young animals. After 6 to 10 days, about 4 mm long, white young hatch. Eggs can be laid at an age of only 3 weeks, but the temperature must not be below 15 ° C. 10 ° C is required for the development of the eggs and 11.7 ° C for the growth of the young.

If Platydemus manokwari is dismembered, each piece grows into a complete animal within 2 weeks. However, there is no evidence of spontaneous division, as is the case with some other land planarians, e.g. B. Bipalium kewense there.

Habitat and Distribution

Platydemus manokwari is native to the island of New Guinea. Here the flatworm can be found in the leaf litter in the tropical rainforests - both primary and secondary forests -, on agricultural areas, in coastal areas and in mountain forests.

food

Platydemus manokwari eats an Eobania vermiculata (in the laboratory). Note the white pharynx , as with all vortex worms, in the middle of the abdomen. The predigested snail has already been almost completely eaten.

Platydemus manokwari prefers shell-bearing land snails as food , but it also preyes on earthworms , nudibranchs , insect larvae and various arthropods . Once it has decimated the snail population, it also switches to other flatworms as prey. Platydemus manokwari is the main enemy of the terrestrial snails in the areas of its distribution it investigates, and it preyes on them in all stages of life, from mature snail eggs to old snails. Only freshly laid snail eggs are not recognized. The animal follows chemical stimuli emanating from the slime tracks of the prey and also pursues them on trees. The flatworm wraps around the prey, everts its trunk-like throat ( pharynx ) and pre- digests it with the help of digestive enzymes before it is sucked in through the mouth opening on the abdomen.

Invasive species

Locations of Platydemus manokwari

Platydemus manokwari was introduced by humans to a number of Pacific islands - partly unintentionally in the flower pots of plants exported from New Guinea, partly deliberately to combat the giant East African snail that was also introduced here . The flatworm has found its way onto numerous tropical and subtropical islands in Micronesia , the Marquesas Islands, Society Islands , Samoa , Melanesia and Hawaii , as well as many Japanese islands. Endemic species of snails can be found on many of these islands , which are adapted to a life with little threat from predators. As K strategists, snails in the Partulidae family reproduce very slowly and sometimes only give birth to around 20 offspring. Platydemus manokwari has been recognized as the main cause of the extinction of endemic snail species in Oceania.

The first describer de Beauchamp found the planarie in 1962 in Queensland ( Australia ). In 2013 the flatworm was found for the first time in a tropical house in the Botanical Garden of Caen (Jardin des Plantes) and thus for the first time in Europe; The first find followed in 2014 on the American continent - in Florida. The zoologist Jean-Lou Justine from the French National Museum of Natural History, who was significantly involved in these investigations, sees the planarie as a threat to “all snail species” in Europe, especially because it survives temperatures of around 10 ° C and longer periods of hunger. In addition, there are no known predators. Because of the great threat that this flatworm species poses to the diversity of the land snail fauna, Platydemus manokwari has been included in the " List of the 100 of the world's worst invasive alien species".

literature

  • Paul de Beauchamp (1962): Platydemus manokwari n. Sp., Planaire terrestre de la Nouvelle-Guinée Hollandaise . Bulletin de la Société Zoologique de France 87, pp. 609-615.

Web links

Commons : Platydemus manokwari  - collection of images, videos and audio files

Individual evidence

  1. ^ R. Ogren (1995): Predation Behavior of Land Planarians . Hydrobiologia 305, pp. 105-111.
  2. ↑ N. Iwai, S. Sugiura et al. (2010): Predation impacts of the invasive flatworm Platydemus manokwari on eggs and hatchlings of land snails . Journal of Molluscan Studies 76 (3), pp. 275-278.
  3. ^ S. Sugiura, Y. Yamaura (2009): Potential impacts of the invasive flatworm Platydemus manokwari on arboreal snails . Biological Invasions 11 (3), pp. 737-742.
  4. ↑ David R. Hopper, Barry D. Smith (1992): Status of tree snails (Gastropoda: Partulidae) on Guam, with a resurvey of sites studied by HE Crampton in 1920 . Pacific Science 46, pp. 77-85. PDF
  5. ^ Jean-Lou Justine, Leigh Winsor, Delphine Gey, Pierre Gros, Jessica Thévenot: The invasive New Guinea flatworm Platydemus manokwari in France, the first record for Europe: time for action is now. . In: PeerJ . 2, 2014, p. E297. doi : 10.7717 / peerj.297 .
  6. ↑ Jean-Lou Justine, Leigh Winsor, Patrick Barrière, Crispus Fanai, Delphine Gey, Andrew Wee Kien Han, Giomara La Quay-Velázquez, Benjamin Paul Yi-Hann Lee, Jean-Marc Lefevre, Jean-Yves Meyer, David Philippart, David G. Robinson, Jessica Thévenot, Francis Tsatsia: The invasive land planarian Platydemus manokwari (Platyhelminthes, Geoplanidae): records from six new localities, including the first in the USA . In: PeerJ . 3, 2015, ISSN  2167-8359 , p. E1037. doi : 10.7717 / peerj.1037 .
  7. ↑ 100 of the world's worst invasive alien species . 2013 update. Global Invasive Species Database. Retrieved October 20, 2015.