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Adaptive radiation & functional morphology
The Salmon Forest Project
Molecular Studies
Lab members

Hydrodynamic and/or sensory function of the adipose fin in Salmonidae

Nicola Temple, M.Sc. project


Occasionally modern taxa show phylogenetic persistence of vestigial or non-functional characters over extended geological time.  These characters often provide insight into common ancestries and are generally interpreted to be retained in modern taxa due to epigenetic constraints in development.  However, the adaptationist program would suggest that characters are retained due to their potential functionality, rather than to constraints. 

One such trait is the adipose fin (Figure 1), a small non-rayed fin located on the midline anterior to the caudal fin and found in eight orders of early teleosts including salmonids.

While observing spawning salmon in a study of  foraging behaviour of bears, it seemed possible that the adipose fin of adult salmon had either hydrodynamic and/or sensory function. Preliminary experiments using a flow chamber were highly consistent with this possibility and these investigations were continued by N. Temple as an M.Sc. program.


Figure 1. Arrow indicates adipose fin on this 
Salmonid (picture extracted from www.fishbase.org ).