Megascolecidae is a large family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of earthworm

Earthworm

Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...

s which has native representatives in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

, Southeast

Southeast Asia

Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...

 and East Asia

East Asia

East Asia or Eastern Asia is a subregion of Asia that can be defined in either geographical or cultural terms...

, and North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. The most ancient lineages of the family show a Gondwana

Gondwana

In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...

n distribution and have been used as evidence of continental drift

Continental drift

Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912...

. Members of the Pheretima

Pheretima

Pheretima is a genus of earthworms found mostly in New Guinea and parts of Southeast Asia.The clitellum is a band of grandular tissue present on segments 14 to 16. Individuals are hermaphroditic and reproduction can be either sexual or parthenogenetic. Female genital pores lie on the ventral...

group of genera (e.g. Amynthas

Amynthas

Amynthas is a genus of earthworms in the family Megascolecidae.-Species:* Amynthas alexandri * Amynthas borealis Panha & Bantaowong, 2011* Amynthas comptus * Amynthas defecta...

) are widely distributed around the tropics, much as some Lumbricidae

Lumbricidae

The Lumbricidae is a family of earthworms which includes most of the earthworm species well known to Europeans. About 33 lumbricid species have become naturalized around the world, but the bulk of the species are in Holarctic: from Canada and the United States The Lumbricidae is a family of...

 are distributed through the temperate zones. Some North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

n native genera – e.g. Arctiostrotus, Argilophilus

Argilophilus

Argilophilus is a genus of western North American earthworms of the family Megascolecidae that are characteristically found under native vegetation...

and Driloleirus

Driloleirus

Driloleirus is an earthworm genus in the family Megascolecidae.This genus includes at least two species:* Driloleirus americanus – giant Palouse earthworm, Washington giant earthworm* Driloleirus macelfreshi – Oregon giant earthworm...

– also belong to this family.

The members of this family have the typical "megascolecine" arrangement of male pores, with vasa deferentia and prostatic ducts

Prostatic ducts

The prostatic ducts open into the floor of the prostatic portion of the urethra, and are lined by two layers of epithelium, the inner layer consisting of columnar and the outer of small cubical cells....

 uniting before opening via a combined pore on segment 18, rather than the "acanthodriline" arrangement (with male pores and pores from one or more pairs of prostates opening separately near segment 18, but never combined on segment 18) as found in the related families Acanthodrilidae

Acanthodrilidae

Acanthodrilidae is an ancient and widely distributed family of earthworms which has native representatives in Australia, New Zealand, South Africa, South America and North America. Interestingly, no native species are known from India nor Asia...

, Octochaetidae and Exxidae.

Megascolecidae genera are either meroic (with multiple nephridia per segment), or have the plesiomorphic holoic arrangement of two nephridia per segment. Some taxa also exhibit enteronephry, where some nephridia, instead of emptying to the body surface, empty into the digestive tract. Seta

Seta

Seta is a biological term derived from the Latin word for "bristle". It refers to a number of different bristle- or hair-like structures on living organisms.-Animal setae:In zoology, most "setae" occur in invertebrates....

e may be lumbricine (plesiomorphic, 8 per segment) or perichaetine (more than 8 setae per segment).