Taxonomic name: Platydemus manokwari
Synonyms:
Common names: Flachwurm (German), flatworm (English)
Organism type: flatworm Platydemus manokwari is a predatory flatworm that threatens endemic gastropods such as rare Pacific Island snails. Invertebrates are highly under-represented in conservation research and there exists a lack of basic biological knowledge about most invertebrate fauna. To avoid an extinction crisis these issues need to be addressed and more education is needed about the importance of invertebrates (such as non-marine molluscs) and their role as a major component of global genetic biodiversity. Description
A worm. Uniform exterior appearance. Adult length 40-65mm, width 4-7mm. Head end more pointed than tail end. Flattened cross section with thickness less than 2mm. Colour of dorsal surface very dark brown, almost black, with a thin medial pale line. Colour of ventral surface pale gray. (de Beauchamp, 1963). Occurs in:
agricultural areas, coastland, natural forests, planted forests, riparian zones, ruderal/disturbed, scrub/shrublands, urban areas, wetlands Habitat description
Generally found in leaf litter in both undisturbed forest and habitats heavily modified by humans. For example, found in leaf litter in high-altitude (>675 m) cloud forest on the island of Pohnpei in Micronesia (Eldredge and Smith, 1995). General impacts
Invertebrate species represent more than 99% of animal diversity; however, they receive much less publicity and attract disproportionately minor research effort relative to vertebrates (Ponder and Lunney 1999, in Lydeard et al. 2004). Nonmarine mollusks include a number of phylogenetically disparate lineages and species-rich assemblages that represent two molluscan classes, Bivalvia (clams and mussels) and Gastropoda (snails, slugs, and limpets) (Lydeard et al. 2004). The global decline of nonmarine mollusks may be facilitated by the spread and introduction of predatory flatworms (Platyhelminthes: Turbellaria), in particular the flatworm Platydemus manokwari.
P. manokwari has been introduced into many locations for use as a biological control agent for the giant African land snail (Achatina fulica). It is an effective predator that poses a serious threat to native snails in the locations where it has been introduced. Vulnerable native snails populations threatened by P. manokwari include endemic Partulidae in Guam (Hopper and Smith, 1992) and Mandarina snail species in the Ogasawara Islands (Japan) (Satoshi 2003).
It is estimated that there are about 4000 native oceanic Pacific island land snails (a number that excludes the continental islands of New Zealand, which harbor an estimated 1350 native species and the island of New Guinea, which probably harbors at least 1000 (Barker 1999, Cowie forthcoming, in Lydeard et al. 2004). These unique native snail faunas are disappearing rapidly (Bauman 1996, Cowie 2001a, Cowie and Robinson 2003, in Lydeard et al. 2004). The Endodontidae, probably the most diverse Pacific island family (Solem 1976, in Lydeard et al. 2004), appear to be completely extinct or reduced to sparse remnant populations on every island they formerly inhabited. All the Partulidae of Moorea (French Polynesia) are extinct in the wild (Murray et al. 1988, in Lydeard et al. 2004). In Hawaii, as many as 90% of the 750 recognized species of land snails are extinct. On Rota (Northern Marianas), 68% of the 43 species are extinct or declining, and in the Samoan archipelago, almost all are declining, although a smaller percentage is extinct (Cowie and Robinson 2003). These estimates suggest that overall perhaps 50% of the land snail fauna of the Pacific islands has disappeared in recent times. Experts suggest that the continued introduction of alien predators such as P. manokwari should be strongly discouraged in order to conserve such unique island snail species (Cowie and Robinson 2003). Uses
Introduced to several islands in the Pacific and Indian Oceans for
biological control of the giant African snail (Achatina fulica), for
example Samoa and Vanuatu (UN FAO, 2002). Considered to be effective at
this task on Bugsuk Island in the Philippines (Muniappan et al., 1986),
in the Maldives (Muniappan, 1987) and on Guam (Muniappan, 1990). Notes
A rhynchodemid flatworm, Platydemus manokwari, was discovered in New Guinea and originally described in 1962 (Kaneda Kitagawa and Ichinohe 1990). Little has been known of its biology except that it is nocturnal, and there apparently is no report on the rearing of this flatworm (Kaneda Kitagawa and Ichinohe 1990). Geographical range
Native range: New Guinea.
Known introduced range: Guam, Hawai‘i, Philippines, Northern Mariana Islands, Australia, Palau, Japan, Maldives, Tonga and Vanuatu. Introduction pathways to new locations
Biological control: Introduced to control the giant African snail (A. fulica). Management information
The resources that are currently available to manage global nonmarine molluscan biodiversity are insufficient. Scientific knowledge is scanty and scattered. Often there are too few staff to manage the existing protected areas, which typically focus on vertebrate species. Because of the lack of resources, mollusks and other less charismatic groups are usually ignored. Nevertheless, regional and species-specific conservation action plans must be developed on the basis of appropriately designed scientific studies, such as that undertaken in the United Kingdom for conservation of the land snail V. moulinsiana (Tattersfield 2003, in Lydeard et al. 2004). To develop such plans, greater integration, coordination, and networking among conservation management agencies, research institutions, and other stakeholders is essential. This approach will ensure that conservation is scientifically based and will help to avoid potentially disastrous ecological, economic, or legal consequences. Furthermore, local and national governments and their agencies, and nongovernmental organizations of all kinds (from international organizations to local conservation societies), must forge relationships to ensure that their goals are not competitive or contradictory and that their actions are in concert. Mollusks must not be ignored when new conservation areas are created. Both new and existing reserves must be adequately managed, with attention paid to mollusks, and in some instances reserves should be established explicitly for mollusks (Lydeard et al. 2004). Nutrition
A predatory species, known to feed on land snails. Reproduction
Hermphroditic, probably cross-fertilising. This species has been nominated as among 100 of the "World's Worst" invaders Reviewed by: Major update under progress
Dr. Robert H. Cowie Center for Conservation Research and Training Principal sources: Barnes, 1968. de Beauchamp, 1963. Eldredge and Smith, 1994, 1995. Hopper and Smith, 1992. Muniappan, 1987, 1990. Muniappan et al., 1986.
Compiled by: Dr. Robert H. Cowie, Center for Conservation Research and Training, University of Hawaii & IUCN/SSC Invasive Species Specialist Group (ISSG)
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Last Modified: Thursday, 13 July 2006
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