Introduction

While Aeolosoma sp. are well known in artificial ecosystems, such as sludge digesters, very little knowledge from field samples is available.  Aeolosoma sp. process large amounts of soil particles and create aerating burrows but their effects have not been quantified.  This movie shows a field sample of Aeolosoma hemprichi feeding on microbial films which cover soil particles. The transparent nature of the worm makes ingestion, peristalsis, and egestion clearly visible.

Oligochaetes are segmented worms with only a limited number of setae, or bristles, for providing purchase during locomotion.  Aeolosoma sp. are small transparent oligochaetes decorated with spots that arise from oil droplets in epidermal cells (1).  Their conspicuous spotted appearance makes them easy to identify in soil or fresh water field samples.  The reddish brown spots of A. hemprichi are shown in this movie (2).  A feature of this genus is the anterior segment, the prostomium, which is ciliated on the underside (3); the prostomium is clearly shown, though cilia are difficult to see.  Aeolosoma sp. reproduce by fission or budding (6), where the anterior part ages but the posterior part does not (4), and they only rarely practice sexual reproduction.

Methods

A Pasteur pipette was used to draw material from the surface of submerged mud in a temporary puddle.  This was transported to the laboratory in an Eppendorf tube.  Approximately 50 µl of water and mud suspension were transferred to a microscope slide and a cover slip was applied.  The slide was examined using conventional bright-field microscopy.  When A. hemprichi was located, its motion was recorded using a Pupil Cam attachment (Ken-A-Vision, Kansas City, MO).

Discussion

Aeolosoma sp. are conspicuous flora in waste disposal systems; for example, they are one of the most abundant worms in activated sludge digesters where their growth is rapid (5) as they prey on microorganisms (7) during an ecological succession that transforms raw sewage into processed sludge.  However, very little information is available for Aeolosoma in natural ecosystems (2) other than that they are abundant in freshwater ponds and streams (6).  Because this worm is transparent, many internal features can be observed in living specimens (3), including digestive processes.  This movie shows a field isolate of A. hemprichi ingesting soil particles which are passed through the gut by peristalsis.  Surface microbes are digested as the particles are moved through the gut in a helical motion and then expelled.

References

1.  Beddard, M. A.  1896.  Oligochaeta,  p. 347–391.  In S. F. Harmer and A. E. Shipley (ed.), The Cambridge natural history, vol. 2.  McMillan, New York, NY. 

2.  Brinkhurst, R. O.  1971.  A guide for the identification of British aquatic oligochaeta.  Scientific publication no. 22, 2nd ed.  Freshwater Biological Association, Cumbria, UK.  http://www.freshwaterlife.org/servlet/BinaryDownloaderServlet?filename=1139315945334_Oligochaeta.pdf.

3.  Herlant-Meewis, H.  1950.  Cyst-formation in Aeolosoma hemprichi.  The Biol. Bull. 99(2):173–180.  http://www.biolbull.org/cgi/reprint/99/2/173.

4.  Hughs, R. N.  1989.  A functional biology of clonal animals.  Chapman and Hall, London, England.

5.  Liang, P., X. Huang, and Y. Qian.  2006.  Excess sludge reduction in activated sludge process through predation of Aeolosoma hemprichi.  Biochem. Eng. J. 28(2):117–122.

6.  Nelson, J. A.  1906.  A note on the occurrence of sexual organs in Aelosoma (sic).  The Ohio Naturalist 6(3):435–438.

7.  Wei, Y., H. Zhu, Y. Wang, J. Li, P. Zhang, J. Hu, J. Liu.  2009.  Nutrients release and phosphorus distribution during oligochaetes predation on activated sludge.  Biochem. Eng. J. 43: 239–245.