Bipalium kewense

Bipalium kewense
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Platyhelminthes
Order:	Tricladida
Family:	Geoplanidae
Genus:	Bipalium
Species:	B. kewense
Binomial name
Bipalium kewense Moseley, 1878
Synonyms
Bipalium manubriatumSharp, 1891 Sphyrocephalus kewensisHallez, 1893 Placocephalus kewensisGraff, 1896 Placocephalus isabellinusGeba, 1909 Bipalium costaricense Hyman, 1939

Bipalium kewense, also known as the shovel-headed garden worm, is a species of large predatory land planarian with a cosmopolitan distribution. ^{[1] [2]} It is sometimes referred to as a "hammerhead flatworm" due to its half-moon-shaped head, but this name is also used to refer to other species in the subfamily Bipaliinae.

Description

Detail of the anterior region of Bipalium kewense

Bipalium kewense is a very long land planarian. Preserved specimens are up to 20 centimetres in length, ^[1] and living specimens may be longer.

The anterior end ("head") is expanded in a transversal semilunate shape and the body is the narrowest just behind the head, in a region called "neck". The dorsal color is light-brown with five black to grey longitudinal stripes that begin at the neck. The median and marginal stripes are narrow and black, very distinctly marked. The lateral stripes (between the median and marginal stripes) are usually grey, broad and with diffuse margins. The neck is usually marked by an incomplete black collar formed by the union of the marginal and lateral stripes, this being one of the main characteristics to distinguish it from similar species. The head usually has a darker color than the background color of the dorsum and lacks stripes. The ventral side has a light ochre color externally and whitish over the creeping sole, which is externally lined by two diffuse grey-violet longitudinal lines. ^{[1] [2]}

Distribution

Bipalium kewense is believed to be native to Southeast Asia, but currently is found worldwide. It has been reported on every continent aside from Antarctica. It was probably introduced by international plant trade, as it is frequently found associated with plant pots. ^{[1] [3] [4]}

The species was first found in 1878 in the area of the Kew Park in the London Borough of Richmond upon Thames, United Kingdom, hence the name kewense. ^[5]

Bipalium kewense capturing an earthworm

Feeding habits

B. kewense is a known predator of earthworms. ^[2] It immobilizes the prey using muscular movements and possibly toxins and then everts its pharynx, connecting it to the earthworm's body and beginning digestion. The digestion seems to be at least partially extracorporeal by means of a collagenolytic enzyme. ^[6]

Toxicity

Bipalium kewense is one of the few terrestrial invertebrates known to produce tetrodotoxin, a neurotoxin that results in paralysis. It is possible that the toxin aids the planarian in subduing its prey as well as in protecting it against predators. ^[7]

Reproduction

Fragment released from the posterior end of an adult worm.

All species of Bipalium are hermaphroditic, but Bipalium kewense has rarely been observed using sexual reproduction as a primary means of reproduction. ^[8]

Asexual fragmentation is the primary means of reproduction in B. kewense in temperate regions. Long specimens usually release body fragments at the posterior end by transverse fission. The fragments are motile and regenerate the head plate and pharynx in a few weeks. Such a reproduction strategy is considered one reason for the successful colonization of this and other species of Bipalium. ^{[1] [2]}

Although there is little evidence of sexual reproduction in these planarians, there have been several reported cases of egg capsules being discovered. The egg capsules discovered had several of the same characteristics of those of B. adventitium, including coloration and incubation period. The most recent egg capsule discovered hatched offspring that did not bear a complete resemblance to adults and were considerably larger in size to that of B. adventitum offspring. ^[8]

Genetics

A 2018 study showed that sequences of Cytochrome c oxidase subunit I (a mitochondrial gene commonly used for barcoding) were identical for all specimens from various countries originating from several continents, suggesting that specimens were clonal. ^[2] The complete mitochondrial genome, 15,666-bp in length, was obtained in 2019 form a specimen collected in France; ^[9] . In 2025, a complete mitogenome was obtained for another specimen, this time coming from Madagascar; only four differences were found between both sequences. ^[10]

References

1. Winsor, L. (1983). "A revision of the cosmopolitan land planarian Bipalium kewense Moseley, 1878 (Turbellaria: Tricladida: Terricola)". Zoological Journal of the Linnean Society. 79 (1): 61–100. doi:10.1111/j.1096-3642.1983.tb01161.x. ISSN   0024-4082.
2. Justine, Jean-Lou; Winsor, Leigh; Gey, Delphine; Gros, Pierre; Thévenot, Jessica (2018). "Giant worms chez moi! Hammerhead flatworms (Platyhelminthes, Geoplanidae, Bipalium spp., Diversibipalium spp.) in metropolitan France and overseas French territories". PeerJ. 6: e4672. doi: 10.7717/peerj.4672 . ISSN   2167-8359. PMC   5969052 . PMID   29844951.
3. Winsor, L.; Johns, P. M.; Barker, G. M. (2004) "Terrestrial planarians (Platyhelminthes: Tricladida: Terricola) predaceous on terrestrial gastropods." In: Barber, G. M. (ed.) Natural enemies of terrestrial molluscs, Wallingford, CABI, 227-278.
4. Justine, Jean-Lou; Winsor, Leigh; Gey, Delphine; Gros, Pierre; Thévenot, Jessica (2014). "The invasive New Guinea flatworm Platydemus manokwari in France, the first record for Europe: time for action is now". PeerJ. 2: e297. doi: 10.7717/peerj.297 . PMC   3961122 . PMID   24688873.
5. Sluys, Ronald (2016). "Invasion of the Flatworms". American Scientist. 104 (5): 288–295. doi:10.1511/2016.122.288.
6. Phillips, Julius; Desden, Marc. H. (1973). "A Collagenase in extracts of the invertebrate Bipalium kewense". Biochemical Journal. 133 (2): 329–334. doi:10.1042/bj1330329. PMC   1177702 . PMID   4353237.
7. Dickens, Joseph Clifton; Stokes, Amber N.; Ducey, Peter K.; Neuman-Lee, Lorin; Hanifin, Charles T.; French, Susannah S.; Pfrender, Michael E.; Brodie, Edmund D.; Brodie Jr, Edmund D. (2014). "Confirmation and Distribution of Tetrodotoxin for the First Time in Terrestrial Invertebrates: Two Terrestrial Flatworm Species (Bipalium adventitium and Bipalium kewense)". PLOS ONE. 9 (6): e100718. Bibcode:2014PLoSO...9j0718S. doi: 10.1371/journal.pone.0100718 . ISSN   1932-6203. PMC   4070999 . PMID   24963791.
8. Ducey, Peter K.; Cerqua, Jamie; West, Lori-Jeanne; Warner, Monica; Eberle, Mark E. (2006). "Rare egg capsule production in the invasive terrestrial planarian Bipalium kewense". The Southwestern Naturalist. 51 (2): 252–255. doi:10.1894/0038-4909(2006)51[252:RECPIT]2.0.CO;2. ISSN   0038-4909. S2CID   85970661.
9. Gastineau, Romain; Justine, Jean-Lou; Lemieux, Claude; Turmel, Monique; Witkowski, Andrzej (2019). "Complete mitogenome of the giant invasive hammerhead flatworm Bipalium kewense" (PDF). Mitochondrial DNA Part B. 4 (1): 1343–1344. doi: 10.1080/23802359.2019.1596768 . ISSN   2380-2359.
10. Gastineau, Romain; Ravelomanana, Andrianjaka; Ramzy, Remondah Rushdy; Koken, Marcel; Soavolamanoro, Suzelyce Eva; Otis, Christian; Boyle, Brian; Gey, Delphine; Winsor, Leigh; Justine, Jean-Lou (2025-05-21). "First confirmed records with molecular data of the terrestrial flatworm Bipalium kewense Moseley, 1878 (Tricladida, Geoplanidae) in Madagascar, Egypt, and South Africa". Check List. 21 (3): 557–564. doi: 10.15560/21.3.557 . ISSN   1809-127X.