''Amynthas mekongianus'', the Mekong worm or Mekong giant earthworm, previously known as ''Megascolex mekongianus'', is a species of

earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...

in the family

Megascolecidae The Megascolecidae is a taxonomic family of earthworms which is native to Madagascar, Australia, New Zealand and both South East Asia and North America. All species of Megascolecidae belong to the Clitellata class. Megascolecidae are a large fami ...

. It is native to the vicinity of the River Mekong in southeastern Asia and may have more than 500 segments and grow to a length of .

Description

The Mekong giant earthworm may grow to a length of up to . Compared to their great length, these worms are relatively slender. The type specimen was one metre long and wide at the broadest point (segment 5). It had 370 segments and was a greyish colour, rather paler on the ventral surface. The

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

was poorly preserved. The second segment had 46

seta In biology, setae (singular seta ; from the Latin word for " bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...

e (bristles) in an incomplete ring with a gap on the ventral surface. Segments 3 to 25 bore about 100 setae each, arranged in a complete ring. The male pores were on segment 17, but this specimen was immature and lacked a

clitellum The clitellum is a thickened glandular and non-segmented section of the body wall near the head in earthworms and leeches, that secretes a viscid sac in which eggs are stored. It is located near the anterior end of the body, between the fourteent ...

Distribution and habitat

The type specimen was recorded as being from "Ban Leum on Mekong River, Annam". This was mistakenly believed to refer to a village in Central Vietnam well away from the River Mekong, but it has been found that "Ban leum" means " forget the place" in the local dialect, and the type locality is thought to be in Thailand or Laos. The river forms a delta at that point and contains extensive mud and sand flats and embankments where the worms live. Pigs forage and fishermen dig worms for bait there.

Ecology

Unlike most other species of giant earthworm, which generally inhabit pastureland, the Mekong worm burrows into the muddy banks of the River Mekong in Laos. The worm forms complex networks of tunnels and brings large quantities of ingested soil to the surface in the form of

worm castings Vermicompost (vermi-compost) is the product of the decomposition process using various species of worms, usually red wigglers, white worms, and other earthworms, to create a mixture of decomposing vegetable or food waste, bedding materials, and ...

. The worms may be collected from the mud, but are more easily collected from underwater at depths around . Little is known of the worm's ecology.

References

{{Taxonbar, from=Q48838660 Megascolecidae Animals described in 1922 Fauna of Laos