Shovel-headed Garden Worm

Appearance

''Bipalium kewense'' is a very long land planarian. Preserved specimens are up to 20 centimetres in length, and living specimens may be longer. The anterior end 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 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. The head usually has a darker color than the background color of the dorsum. The ventral side is white and externally lined by two diffuse grey longitudinal lines.

Distribution

''Bipalium kewense'' is believed to be native to Southeast Asia, but currently is found worldwide. It was probably introduced by international plant trade, as it is frequently found associated with plant pots.

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''.

Reproduction

All species of ''Bipalium'' are hermaphroditic, but ''Bipalium kewense'' has rarely been observed using sexual reproduction as a primary means of reproduction. Asexual fragmentation is the primary means of reproduction in ''B. kewense'' in temperate regions. 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.

Food

''B. kewense'' is a known predator of earthworms. 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.

Defense

''Bipalium kewense'' is 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.