Form Fits Function

The Anguilla rostrata’s form has a lot to do with what stage of their life cycle they are in but it also has a depends on the environment that these American eels are living. When they first hatch the eels are small and thin juveniles called glass eels. This name is fondly given to the larvae because they seem so translucent that the eel can be considered to look like glass  As the Anguilla rostrata grow into the elver phase they become larger and start to form pigmentation (Oliveira). The third phase is the yellow phase as shown in the picture on the right, which shows a quite large eel for the yellow phase. The final phase the pigmentation is complete and they turn a darker shade of brown depending on the surrounding estuary bottom. The dark pigmentation on the dorsal side helps camouflage them from predators. Especially attacks from the sky by eagle and other birds that could spot them without this camouflage. This camouflage is perfect for the murky estuaries and floor bottoms that the eel is accustomed to in its development.




 The long sleek body is great for getting into cracks and crevices for ambush attacks. Another form of the American eel is their beak shaped nose that is good at getting into small areas. The American eel can actually achieve fairly decent size as you see in the photo. Their form of movement is a side to side propulsion by is tail. This motion needs to be sustainable for the large migration back out in to the ocean from as far inland as Wisconsin and other Midwest states. This trip will take them a long time so the effortless back and forth motion of their tail is very important to not expend too much energy.




The Anguilla rostrata form fits its function perfectly by blending in easily and living near the bottom of estuaries to feed. It can be deduced that the Anguilla rostrata spend most of their lives on the bottom of the estuaries from Ogden’s work on their food habits showing that eels feed on crayfish and small slow moving bottom feeders. These can include you white suckers (Castomus coAmerican Eelmmersoni) and the fallfish (Semotilus corporalis), that are small enough for them to ingest. It is safe to say that when you are talking about a form fitting a function well the Anguilla rostrata is a perfect example of this for each of its four stages of life.











To learn about the Reproduction and life history of the Anguilla rostrata click here