What's in a name?

As previously mentioned, Eisenia fetida is also known as the red worm, red wiggler, brandling worm, dung worm, and the tiger worm.  Each of these names including its scientific name Eisenia fetida relate to some it its physical characteristics. 

'Red' obviously refers to the worm's dark reddish color

'To brandle' refers to a movement of shaking or thrashing - which can also be described as 'wiggling.'  This is a common movement for Eisenia fetida when it is harshly handled or fears predation.

'Tiger' refers to the stripes.  This worm has a striped appearance due to its body segments.

'Dung' refers to one of the worm's common habitats.  

'fetida' is derived from the Latin word 'fetid' which refers to a foul odor.  This would be the coelomic fluid that this worm ejects from its body when roughly handled. 

 

Adaptation

The traits listed above that have earned this organism its common names create an excellent introduction into its main adaptations.

Color
	The color of Eisenia fetida allows it to blend in well within its primary habitats of soil and organic debris.
Segments
	Segmentation in earthworms can be seen as the rings that compose their bodies.  The first ring or segment is the head and the last segment is the anus.  Segments provide the worm with the ability to burrow more efficiently than it would be able to without segmentation.  Since these creatures constantly crawl through soil and debris this is an especially important adaptation.  These segments also allow the worm’s body sections to specialize.  Though there are duplications, each segment has a specific role or task in daily functions of the worm.  Internally, the segmentations can be seen by the presence of septum which are like walls that enclose coelomic fluid in each segment. Segmentation in this earthworm along with other earthworms allows for regeneration of certain parts of the body.  In fact, Eisenia fetida can regenerate the anterior segments of its body from segments 23 and 24 and the posterior segments of its body from segments 20 and 21.
Coelom
	A coelom is an internal fluid-filled cavity.  It creates space for internal organs.  It also allows for movement by acting as a hydrostatic skeleton.  This hydrostatic skeleton makes a medium which the muscles of the worms can push against and increase the efficiency of movements. Within its coelom, the Eisenia fetida has developed a fluid that can be ejected when the worm is handled unfavorably.  This adaptation is most likely a defense mechanism used to ward off would-be predators.  This coelomic fluid is described as “nutty” and is responsible for the ‘fetid’ (which means bad smelling in Latin) portion of its name.  Some times the worms appear yellowish in color around the anus because of the build up of coelomic fluid.  This phenomenon can be seen in the lower two worms in the photo to the right.
Nervous tissue
	The annelids exhibit a greater deal of nervous tissue development than lesser evolved organisms.  The majority of this tissue is in the anterior of the worm it its head region.  There is also a great deal of nervous development along the bottom, or dorsal, side of the worm that helps it control movement along a substrate. The first (head) segment contains a pair of cerebral ganglia which are nerve cords that act like eyes for the worm.  Presumably this pair of cerebral ganglia are responsible for Eisenia fetida's great sensitivity to light.
Chaetae
	Like its class (Oligochaeta) implies, this worm has 'few chaetae.'  More specifically it has eight chaetae per segment that are grouped in pairs within the segment.  These are tiny little bristles extending from the body that are made of chitin.  Though there are only 'few,' they are extremely important and facilitate movement through and over substrates.  Other Annelids sometimes have parapodia which are basically little legs.  These would actually hinder the Oligochaetes by making passage through a substrate more difficult.
Clitellum
	The clitellum is a specialized structure that aids in reproduction.  Find out more information by clicking on the life history and reproduction page.
Digestive Organs
	Eisenia fetida also has some specific adaptations which are specifically related to its nutrient acquisition and digestion such as nephridia, a gizzard, a circulatory system, and a typhlosole.  More information can be found on the nutrition page.

Eisenia fetida appears to have been more adaptive to environmental conditions than its composting colleagues.  It can optimally grow and reproduce is temperature ranges from 15 -25 degrees Celsius (59-77 degrees Fahrenheit), moisture content ranges from 43-90 %, and pH levels between 5 and 9 (Blakemore).  These ranges are for optimal growth and reproduction.  It can survive in conditions more extreme than these, but the conditions would be detrimental to some form of growth or reproduction.  This species’ ability to adapt to wider ranges of environmental conditions has made it more   cosmopolitan than similar species used for vermicomposting.