Megascolecidae

Giant Gippsland earthworm Megascolides australis, from Bartholomew (1885).

Belongs within: Acanthodrilidae.
Contains: Woodwardiella, Notoscolex, Plutellus, Megascolex, Argilophilini, Amynthas, Pheretima.

Pontodrilus: earthworms by sea
Published 14 June 2017

Earthworms are primarily a terrestrial and freshwater group, sensitive to changes in the quality of their habitat. But there are some earthworm species that are tolerant of more saline environments. One such species is Pontodrilus litoralis, a widespread earthworm found in warm coastal habitats around the world, being recorded from such far-flung places as the Caribbean, the Mediterranean, Australia and Japan. The species is found in sandy or muddy soils in coastal habitats, including beaches, estuaries and around the roots of mangroves, and is able to tolerate salinities from 5 to 25 parts per thousand—that is, from fresh water to close to the standard salinity of sea water (Blakemore 2007).

Pontodrilus litoralis in its natural habitat, from here.

Pontodrilus litoralis is one of five species currently recognised in the genus Pontodrilus, though many more have been recognised in the past (Blakemore, 2007, listed eighteen species and subspecies now regarded as synonyms of P. litoralis). Characteristic features of the genus include an absence of nephridia in the anterior segments, and tubular prostrate organs opening to male pores on the eighteenth segment. The other Pontodrilus species have more restricted, non-coastal ranges; one, P. lacustris, is found free-swimming in Lake Wakatipu in New Zealand, whereas the other three are found in terrestrial habitats in Sri Lanka, China and Tasmania.

How P. litoralis achieved its wide distribution is currently unknown. If it arose prior to the separation of the land-masses on which it is now found then it would have had to have survived almost unchanged for hundreds of millions of years, which seems on the face of it unlikely. It seems more credible that it has dispersed more recently from its original point of origin, but while its green, spindle-shaped cocoons are often found attached to floating vegetation we do not know how long they can stand immersion in full-strength salt water. Nor do we know just where P. litoralis originated. It was first described in 1855 from the French Riviera so many authors have assumed the species is Mediterranean in origin. However, the distribution of related species seems to make an Indo-Pacific origin more likely. It may well be that P. litoralis was spread from its original home by humans, carried with rocks and sand used for ballast.

Systematics of Megascolecidae
Megascolecidae [Megascolecina]
| i. s.: HoplochaetellaJ88
| Howascolex madagascariensisM13
| PolypheretimaJG19
| |--P. brevis (Rosa 1898) [=Pheretima brevis]JG19
| `--P. elongata (Perrier 1872)R93
|--DiplogastrinaeJ31
`--Megascolecinae [Megascolecini, Perionychini]J88
| i. s.: *Fletcherodrilus unicus (Fl. 1888)M07, F90 [=Cryptodrilus unicusM07]
| Spenceriella Michaelsen 1907M07
| |--*S. notabilis [=Diporochaeta notabilis]M07
| |--S. gigantea [=Diporochaeta gigantea]M07
| |--S. lateralis [=Perichaeta lateralis]M07
| |--S. mapplestoni [=Diporochaeta mapplestoni]M07
| `--S. shakespeari [=Diporochaeta shakespeari]M07
| Perionychella Michaelsen 1907M07
| |--*P. dendyi [=Perichaeta dendyi]M07
| |--P. canaliculata [=Perichaeta canaliculata]M07
| |--P. pritchardi [=Megascolex pritchardi]M07
| `--P. scolecoides [=Perichaeta scolecoides]M07
| Didymogaster Fletcher 1886J31, F86a
| `--*D. sylvaticus Fletcher 1886F86a
| *Perissogaster excavataM07
| *Plionogaster horsti [=Perichaeta horsti]M07
| WoodwardiellaJ31
| NotoscolexJ31
| Pontodrilus Perrier 1874J31, B07 [Pontodrilidae]
| |--P. litoralis (Grube 1855)B07 (see below for synonymy)
| |--P. agnesae Stephenson 1915B07
| |--P. lacustris (Benham 1903)B07 [=Plutellus lacustrisM07]
| |--P. primoris Blakemore 2000B07
| `--P. sinensis Chen & Zhifang 1977B07
| PlutellusJ31
| MegascolexJ31
| ArgilophiliniB07
| Reflechtodrilus sigillatusB07
| AnisochaetaB07
| |--A. cormieriB07
| `--A. hugalliB07
| AmynthasB07
| Begemius queenslandicusB07
| Archipheretima pandanophilaJD12
| TerriswalkeriusJD12
|--Heteroporodrilus tryoni (Fletcher 1889)J88
`--+--Cryptodrilus Fletcher 1886J88, F86a
| |--*C. rusticus Fletcher 1887F86a, J88
| |--C. fasciatus Fletcher 1890F90
| |--C. manifestusM07
| |--C. purpureusF90
| |--C. saccarius Fletcher 1886F86b (see below for synonymy)
| |--C. simulans Fletcher 1890F90
| `--C. tryoni Fletcher 1890F90
`--+--DigasterJ88
| |--*D. lumbricoides Perrier 1872M07, F86a
| |--D. armifera Fletcher 1886F86b
| |--D. bradburyi Jamieson 1970J88
| `--D. minorM13
`--+--*Perionyx excavatus Perrier 1872M07, J88
`--+--Celeriella bursata Jamieson 1977J88
`--+--DiporochaetaJ88
| |--*D. intermedia (Beddard 1889)J88 (see below for synonymy)
| |--D. alsophila [=Perichaeta alsophila]M07
| |--D. aquaticaM07
| |--D. chathamensisM07
| |--D. euzonaM07
| |--D. gigantea Benham 1905B49
| |--D. kershawiB07
| `--D. terraereginae (Fletcher 1890)M07, F90 [=Perichaeta terraereginaeM07]
`--+--+--Lampito sylvicola Michaelsen 1907J88
| `--PheretimaJ88
`--MegascolidesJ88
|--*M. australis McCoy 1878M07, J88
|--M. cameroniM07
|--M. esculentus [=Tokea esculenta]M07
|--M. nokanenaensis Michaelsen 1907M07
|--M. orthostichon [=Hypogaeon orthostichon]M07
|--M. polynephricus [=Cryptodrilus polynephricus]M07
|--M. reptans [=Notoscolex reptans]M07
`--M. tenuis [=Cryptodrilus tenuis]M07

Cryptodrilus saccarius Fletcher 1886F86b [incl. C. saccarius var. montanus Fletcher 1890F90, C. saccarius var. robustus Fletcher 1890F90]

*Diporochaeta intermedia (Beddard 1889)J88 [=Perichaeta intermediaM07; incl. P. novaezelandiae (n. n.)M07]

Pontodrilus litoralis (Grube 1855)B07 [=Lumbricus litoralisB07, L. littoralisB07; incl. P. albanyensis Michaelsen 1907B07, P. arenae Michaelsen 1892B07, P. arenicola Schmarda 1861B07, P. bermudensis Beddard 1891B07, P. matsushimensis chathamianus Michaelsen 1899B07, P. crosslandi Beddard 1907B07, P. albanyensis var. cygni Jackson 1931B07, P. ephippiger Rosa 1898B07, P. bermudensis f. ephippigerJ31, P. gracilis Gates 1943B07, P. hesperidum Beddard 1894B07, P. michaelseni hortensis Eisen 1900B07, P. matsushimensis indica Michaelsen 1935B07, P. insularis Rosa 1891B07, P. laccadivensis Beddard 1903B07, P. ephippiger laysanianus Michaelsen 1899B07, *P. marionis Perrier 1874B07, P. matsushimensis Iizuka 1898B07, P. michaelseni Eisen 1895B07]

*Type species of generic name indicated

References

[B49] Benham, W. B. 1949. A yard-long earthworm, Notoscolex hakeaphilus. Transactions and Proceedings of the Royal Society of New Zealand 77 (3): 346–350.

[B07] Blakemore, R. J. 2007. Origin and means of dispersal of cosmopolitan Pontodrilus litoralis (Oligochaeta: Megascolecidae). European Journal of Soil Biology 43: S3–S8.

[F86a] Fletcher, J. J. 1886a. Notes on Australian earthworms. Part I. Proceedings of the Linnean Society of New South Wales, series 2, 1 (2): 523–574, pls 8–9.

[F86b] Fletcher, J. J. 1886b. Notes on Australian earthworms. Part II. Proceedings of the Linnean Society of New South Wales, series 2, 1 (3): 943–973, pl. 13.

[F90] Fletcher, J. J. 1890. Notes on Australian earthworms. Part VI. Proceedings of the Linnean Society of New South Wales, series 2, 4 (3): 987–1019.

[J31] Jackson, A. 1931. The Oligochaeta of south-western Australia. Journal of the Royal Society of Western Australia 17: 71–136.

[JG19] James, D. J., P. T. Green, W. F. Humphreys & J. C. Z. Woinarski. 2019. Endemic species of Christmas Island, Indian Ocean. Records of the Western Australian Museum 34 (2): 55–114.

[JD12] James, S. W., & S. K. Davidson. 2012. Molecular phylogeny of earthworms (Annelida: Crassiclitellata) based on 28S, 18S and 16S gene sequences. Invertebrate Systematics 26: 213–229.

[J88] Jamieson, B. G. M. 1988. On the phylogeny and higher classification of the Oligochaeta. Cladistics 4: 367–402.

[M07] Michaelsen, W. 1907. Oligochaeta. Die Fauna Südwest-Australiens 1 (2): 115–232, 2 pls.

[M13] Michaelsen, W. 1913. Die Oligochäten von Neu-Caledonien und den benachbarten Inselgruppen. In: Sarasin, F., & J. Roux (eds) Nova Caledonia: Forschungen in Neu-Caledonian und auf den Loyalty-Inseln. A. Zoologie vol. 1 pt 3 pp. 173–280. C. W. Kreidels Verlag: Wiesbaden.

[R93] Righi, G. 1993. Some Megadrili Oligochaeta of the Caribbean region. Revue Suisse de Zoologie 100 (1): 137–142.

Leave a comment

Your email address will not be published. Required fields are marked *