''Bipalium'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of large

predatory Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

land planarian Geoplanidae is a family of flatworms known commonly as land planarians or land flatworms. These flatworms are mainly predators of other invertebrates, which they hunt, attack and capture using physical force and the adhesive and digestive proper ...

s. They are often loosely called "hammerhead worms" or "broadhead planarians" because of the distinctive shape of their head region. Land planarians are unique in that they possess a "creeping sole", a highly ciliated region on the

ventral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

that helps them to creep over the substrate. Native to Asia, several species are invasive to the United States, Canada, and Europe. Some studies have begun the investigation of the evolutionary ecology of these invasive planarians.

Etymology

The name ''Bipalium'' comes from Latin ''bi-'', "two" + ''pala'', "shovel" or "spade", because species in this genus resemble a

pickaxe A pickaxe, pick-axe, or pick is a generally T-shaped hand tool used for Leverage (mechanics), prying. Its head is typically metal, attached perpendicularly to a longer handle, traditionally made of wood, occasionally metal, and increasingly ...

Description

The genus ''Bipalium'' was initially defined by Stimpson to include land planarians with the head broadened, forming a head plate. Later, in 1899,

Ludwig von Graff Ludwig Graff de Pancsova (2 January 1851 – 6 February 1924), known as Ludwig von Graff, was an Austrian zoologist born in Pancsova. In 1871, he received his medical degree in Vienna, afterwards studying zoology at the University of Graz. In 1 ...

divided it into three genera according to the shape of the head: #''Bipalium'': with a well-developed head plate, much broader than long, and with elongated lateral auricles #''Perocephalus'': rudimentary head plate, not much broader than the body #''Placocephalus'': flat head plate with a circular outline Josef Müller, in 1902, considered that no sufficient anatomical basis existed for this distinction, and reunited them under ''Bipalium''. Later, von Graff accepted Müller's conclusions. Towards the end of the 20th century, Robert E. Ogren and

Masaharu Kawakatsu is a Japanese zoologist known for his studies on the taxonomy and ecology of planarians. Life Masaharu Kawakatsu was born in 1929 in the Asahi, Hokkaido, Asahi village, Kameoka town, Kyoto Prefecture, Japan, son of Masakazu Kawakatsu, a squir ...

started a series of publications called "The Land Planarian Index series" in which they reviewed and organized all taxonomic information regarding land planarians. At first, they retained all broad-headed planarians in the genus ''Bipalium'', but later split them into four genera based on the anatomy of the

reproductive organs A sex organ, also known as a reproductive organ, is a part of an organism that is involved in sexual reproduction. Sex organs constitute the primary sex characteristics of an organism. Sex organs are responsible for producing and transporting ...

: ''Bipalium'', '' Novibipalium'', '' Humbertium'', and '' Diversibipalium''. Under this scenario, the genus ''Bipalium'' is defined as containing broad-headed land planarians with simple copulatory organs, without accessory ducts or copulatory bursa, and with a fold of tissue separating the male and female exit ducts.

Feeding habits

''Bipalium'' species are

. Some species prey on

earthworm An earthworm is a soil-dwelling terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (or subclass, depending on the author) Oligochaeta. In classical systems, they we ...

s, while others may also feed on

mollusks Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The num ...

. These flatworms can track their prey. When captured, earthworms begin to react to the attack, but the

flatworm Platyhelminthes (from the Greek language, Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") is a Phylum (biology), phylum of relatively simple bilaterian, Segmentation (biology), ...

uses the muscles in its body, as well as sticky secretions, to attach itself to the earthworm to prevent escape. The planarians cover, or cap, the

prostomium The prostomium (From Ancient Greek, meaning "before the mouth"; : prostomia; sometimes also called the "acron") is the Cephalization, cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not in ...

peristomium The peristomium is the first true body segment in an annelid worm's body in the anterior end. It is directly behind the prostomium and contains the mouth, tentacular cirri, and sometimes feeding palps, which may instead occur on the prostomium. If ...

, and anterior end to stop the violent reaction by the earthworm. To feed on their prey, species of ''Bipalium'' often evert their pharynges from their mouths, located on the midventral portion of their bodies, and secrete enzymes that begin the digestion of the prey. The liquefied tissues are sucked into the branching gut of the flatworms by ciliary action.

Reproduction

Reproduction in ''Bipalium'' may be asexual or sexual and all species are

hermaphroditic A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

. '' B. adventitium'' reproduces sexually and creates egg capsules, which hatch around 3 weeks post-deposition. The egg capsules have a tough exterior and generally contain multiple juveniles. '' B. kewense'' have rarely been observed using egg capsules as a primary method of reproduction.

Asexual fragmentation Fragmentation in multicellular or colonial organisms is a form of asexual reproduction or cloning, where an organism is split into fragments upon maturation and the split part becomes the new individual. The organism may develop specific organs o ...

is its main reproductive strategy in temperate regions and most individuals never develop sexual organs. Juveniles of this species, unlike ''B. adventitium'', do not appear the same coloration as parents in their early days.

Toxicity

In 2014, the presence of

tetrodotoxin Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an Order (biology), order that includes Tetraodontidae, pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Alt ...

, a very dangerous

neurotoxin Neurotoxins are toxins that are destructive to nervous tissue, nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insult (medical), insultsSpencer 2000 that can adversely affect function ...

, was recorded in '' B. adventitium'' and '' B. kewense''. It is the first record of tetrodotoxin in terrestrial invertebrates.

Invasive species

Little is known about the ecology of terrestrial planarians, but research has been done on different genera and species, including several native and invasive species in Brazil, '' Arthurdendyus triangulatus'', '' Rhynchodemus'' and ''Bipalium''. As of 2007, four invasive species of ''Bipalium'' were known in the United States: ''B. adventitium'', ''B. kewense'', ''B. pennsylvanicum'', and ''B. vagum''. These planarians are thought to have come to the US on infected plants and soil. ''

Bipalium kewense ''Bipalium kewense'', also known as the shovel-headed garden worm, is a species of large predatory land planarian with a cosmopolitan distribution. It is sometimes referred to as a "hammerhead flatworm" due to its half-moon-shaped head, but this ...

'' has been found commonly in American greenhouses since 1901. This species is a voracious predator of earthworms, and has been identified as a nuisance in the southern USA in earthworm-rearing beds. Control of the species is difficult due to the lack of predators. As noted by the

University of Florida The University of Florida (Florida or UF) is a public university, public land-grant university, land-grant research university in Gainesville, Florida, United States. It is a senior member of the State University System of Florida and a preem ...

IFAS department,

Other animals rarely devour land planarians, since surface secretions appear distasteful, if not toxic. Protozoans, including flagellates, ciliates, sporozoans, and nematodes have been detected in land planarians. Because of their cannibalistic habit, land planarians may be their own worst enemy.

Specimens of ''

Bipalium adventitium ''Bipalium adventitium'', the wandering broadhead planarian, is a land planarian in the subfamily Bipaliinae. It has been accidentally introduced in the United States, where it is considered invasive. Appearance Most adult individuals of ''B. a ...

'' are characterized by a single dark dorsal stripe. They were first discovered in the US in California and New York but have been found in Illinois as well as most northern states. In 2019, they were discovered in Montreal, Canada. ''B. kewense'' have five dark dorsal stripes and a partial dark collar. They have undergone several name changes since their discovery in North America. ''B. kewense'' is commonly found across the southern regions of the US. ''B. kewense'' is found worldwide in tropical and subtropical regions.'' Bipalium pennsylvanicum'' is characterized by its dark brown head and three dorsal stripes. As of 2014, it has only been found in

Pennsylvania Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...

and in coastal

South Carolina South Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders North Carolina to the north and northeast, the Atlantic Ocean to the southeast, and Georgia (U.S. state), Georg ...

. '' Bipalium vagum'' is characterized by two dark dorsal blotches on the head, a thick black band around the neck, and three dark dorsal stripes. This species has been found in several

Gulf Coast The Gulf Coast of the United States, also known as the Gulf South or the South Coast, is the coastline along the Southern United States where they meet the Gulf of Mexico. The coastal states that have a shoreline on the Gulf of Mexico are Tex ...

states, and in 2022, specimens were located extending further north into

Arkansas Arkansas ( ) is a landlocked state in the West South Central region of the Southern United States. It borders Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, Texas to the southwest, and Oklahoma ...

. Recently, it was found in Mumbai, India.

Image gallery

File:Bipalium kewense sighted in Austin, Texas 02.JPG, ''Bipalium kewense'' sighted in Austin, Texas File:Bipalium kewense sighted in Austin, Texas 01.JPG, Close up of head of ''Bipalium kewense'' File:Bipalium from GA.jpg, Specimen of ''Bipalium'' found in

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

, United States File:Hammerhead worm 2.jpg, Hammerhead worm found in

Kerala Kerala ( , ) is a States and union territories of India, state on the Malabar Coast of India. It was formed on 1 November 1956, following the passage of the States Reorganisation Act, by combining Malayalam-speaking regions of the erstwhile ...

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

File:Hammer Headed Worm.jpg, Hammerhead worm found in Chennai and Coimbatore, India File:Bipalium kewense.ogv, Video of a ''Bipalium'' sp. from Mérida, Yucatán, Mexico File:Hammerhead Worm.jpg, Hammerhead worm seen in Kolkata, India File:Bipalium, Kayamkulam, Alappyzha, Kerala, India.jpg, alt=Bipalium, Hammerhead worm found in Kerala, India File:Hammerhead worm.jpg, Hammerhead worm found in Bihar, India

Species

The genus ''Bipalium'' currently includes the following species: *'' Bipalium adensameri'' *'' Bipalium admarginatum'' *''

'' *'' Bipalium albo-coeruleus'' *'' Bipalium alternans'' *'' Bipalium bengalensis'' *'' Bipalium bergendali'' *'' Bipalium bimaculatum'' *'' Bipalium chhatarpurensis'' *'' Bipalium choristosperma'' *'' Bipalium costaricensis'' *'' Bipalium crassatrium'' *'' Bipalium distinguendum'' *'' Bipalium dubium'' *'' Bipalium fuscatum'' *'' Bipalium fuscolineatum'' *'' Bipalium gestroi'' *'' Bipalium glandiantrum'' *'' Bipalium glandulosa'' *'' Bipalium glaucum'' *'' Bipalium gracilis'' *'' Bipalium graffi'' *'' Bipalium haberlandti'' *'' Bipalium hilgendorfi'' *'' Bipalium janseni'' *'' Bipalium javanum'' *'' Bipalium kaburakii'' *'' Bipalium katoi'' *''

'' *'' Bipalium kisoense'' *'' Bipalium kraepelini'' *'' Bipalium manubriatum'' *'' Bipalium marginatum'' *'' Bipalium mjobergi'' *'' Bipalium mondimentum'' *'' Bipalium monolineatum'' *'' Bipalium moseleyi'' *'' Bipalium muninense'' *'' Bipalium myadenosium'' *'' Bipalium nigrum'' *'' Bipalium nobile'' *'' Bipalium ochroleucum'' *'' Bipalium pennsylvanicum'' *'' Bipalium penrissenicum'' *'' Bipalium persephone'' *'' Bipalium poiense'' *''

Bipalium rhytidoantrum ''Bipalium'' is a genus of large predatory land planarians. They are often loosely called "hammerhead worms" or "broadhead planarians" because of the distinctive shape of their head region. Land planarians are unique in that they possess a "creep ...

'' *'' Bipalium rigaudi'' *'' Bipalium robiginosum'' *''

Bipalium rugiantrum ''Bipalium'' is a genus of large predatory land planarians. They are often loosely called "hammerhead worms" or "broadhead planarians" because of the distinctive shape of their head region. Land planarians are unique in that they possess a "creep ...

'' *'' Bipalium semperi'' *''

Bipalium simrothi ''Bipalium'' is a genus of large predatory land planarians. They are often loosely called "hammerhead worms" or "broadhead planarians" because of the distinctive shape of their head region. Land planarians are unique in that they possess a "cree ...

'' *'' Bipalium strubelli'' *'' Bipalium sudzukii'' *'' Bipalium sylvestre'' *'' Bipalium tetsuyai'' *'' Bipalium unistriatus'' *'' Bipalium univittatum''

*'' Bipalium vagum'' *'' Bipalium virile'' *'' Bipalium weismanni'' *'' Bipalium wiesneri'' *''

Bipalium somii ''Bipalium'' is a genus of large predatory land planarians. They are often loosely called "hammerhead worms" or "broadhead planarians" because of the distinctive shape of their head region. Land planarians are unique in that they possess a "creep ...

References

External links

''Bipalium''
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University of Maine The University of Maine (UMaine) is a Public university, public Land-grant university, land-grant research university in Orono, Maine, United States. It was established in 1865 as the land-grant college of Maine and is the Flagship universitie ...

Turbellarian taxonomic database
Land planarians
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Texas A&M University Texas A&M University (Texas A&M, A&M, TA&M, or TAMU) is a public university, public, Land-grant university, land-grant, research university in College Station, Texas, United States. It was founded in 1876 and became the flagship institution of ...

Insects in the City
Photograph of ''B. nobile''

Photograph of ''B. simrothi''
{{Taxonbar, from=Q3761757 Geoplanidae Rhabditophora genera Taxa named by William Stimpson Articles containing video clips