Earthworms  and  Allies   -   Subclass:  Oligochaeta


"Earthworms, though in appearance a small and despicable link in the chain of nature, yet, if lost, would make a lamentable chasm."
Gilbert White, 'parson-naturalist',  (1720 - 1793).
​      First described and named by the Prussian zoologist, Adolph E. Grube in 1850 the Oligochaeta are a subclass of Annelids containing around 10,000 known species.  Currently accepted taxonomy sees it divided into eleven orders, species from up to five of which may be encountered in the Northern Rivers.   Its is estimated there are some 1000+ species of Oligochaetes endemic to Australia and at least 80 exotic species.  The Northern Rivers is (conservatively) expected to be home to about five  to seven percent of these numbers.  
      With fossils of Oligochaeta being quite rare, most of our knowledge about their evolution is obtained from molecular studies.  Helpful also is an insight in the current distribution of the numerous species that exist today.  It is quite certain that earthworms and some of their closest related species have been around since the Triassic period, 252 - 201 Mya.  Since then their appearance has not changed much at all and any new adaptations that evolved were likely to be responses environmental factors or adjustments in certain behaviours.
Picture
Image 1. - A. Bartholomew - 'Giant Gippsland Earthworm, Megascolides australis.' Source: Museums Victoria, Public Domain.
      Oligochaeta all have a very similar bodyplan but they vary wildy in length; the smallest measuring a mere one half of a millimeter and the longest an astonishing three meters.   There are marine and freshwater species that burrow in the sediments  or live among the plants in tidal or shallow environments.   Terrestrial species in Australia prefer moist soils in areas where there is at least 400 mm of rainfall per annum although relict species do exist as evidenced by the recent discovery of a new species from Rupee Station, 10 kilometers north-east of broken Hill.  This species has obviously survived the dramatic climate changes Central Australia has undergone over the past thousands to millions of years.
     Gilbert White (see quote at the top of the page) was a British clergyman who, like so many others of his calling considered the study of nature as an extension of their religious beliefs.  He is seen by many as the very first 'ecologist' and is most known for his book: Natural History and Antiquities of Selborne, (1789).  This book has been in continuous print since its' publication and, as of 2007, was nearing 300 editions.
References  and  links:
​
>      Image 1.     Image by Arthur Bartholomew,   'Giant Gippsland Earthworm, Megascolides australis.'  Source: Museums Victoria, Public Domain.

​>      Abbott, I.,  (1994).   'Distribution of the native earthworm fauna of Australia: a continent-wide perspective.'   Australian Journal of Soil Research 32, pp. 117–126
>      Dyne, G.,  (2021).    'A new genus and species of earthworm (Oligochaeta: Megascolecidae) from semi-arid Australia.'   Records of the Australian Museum. 73. 123–129.
​doi: 10.3853/j.2201-4349.73.2021.1769. 

         https://australian.museum/learn/animals/worms/australian-earthworms/
         https://blogs.biomedcentral.com/bmcseriesblog/2017/06/01/the-evolution-of-earthworms/
         https://www.britannica.com/science/Triassic-Period
       https://en.wikipedia.org/wiki/Adolph_Eduard_Grube
       https://en.wikipedia.org/wiki/Gilbert_White
       https://en.wikipedia.org/wiki/Relict_(biology)​
​
Header photo:

Note:  Copyright rules vary.  Please contact the editor prior to using any of the images published on this site.