Faculty Detail   
Name STEVEN J ZEHREN
  
Campus Address VH G 08 Zip 0019
Phone  (205) 934-4494
E-mail  szehren@cellbio.bhs.uab.edu
Other websites
    

Faculty Appointment(s)
Appointment Type Department Division Rank
Primary  Dept of Medical Education  Dept of Medical Education Professor

Biographical Sketch 
Dr. Steven J. Zehren (b. 1946), Assistant Professor, completed his undergraduate studies at the Unversity of Wisconsin (B.S. in zoology, 1969) and received a Ph.D. in anatomy from the University of Chicago in 1974. He completed his postdoctoral training on the comparative osteology and phylogeny of zeiform fishes at the United States National Museum of Natural History in Washington, D.C. and has continued this research at Birmingham (1975 to present). Dr. Zehren joined the faculty in 1975 as an Instructor (1975 to 1983), and was appointed as an Assistant Professor in 1983.

Research/Clinical Interest
Title
Description
My teaching interests are in the fields of ichthyology and systematics. Currently I am studying the osteology and evolutionary relationships of the boarfishes, a group of marine teleosts of world-wide distribution. Boarfishes are members of the Acanthopterygii, a much larger group the anatomy and relationships of which are very poorly known. My research is aimed at solving a particular problem (relationships of boarfishes) and providing a more complete database for other workers studying acanthopterygian relationships. Data for my research are obtained from preserved museum specimens. Specimens are cleared and stained by placing them in a trypsin solution (to dissolve the soft tissues) and staining the cartilages and bones with alcian blue and alizarin red S dye. After dissecting them under a microscope, osteological descriptions and illustrations are made. Anatomical similarities among species are analyzed using cladistic principles. Thus, only derived (not primitive) similarities are used to determine evolutionary relationships. The primitive vs. derived nature of similarities is determined by the outgroup method. This method involves examining the distribution of anatomical characters in the group most closely related to the study group (in this case, boarfishes). The functional significance of characters is also taken into consideration. The recognition of functional complexes of characters (= functionally correlated characters) is important in order to avoid redundancy in the data set and to ensure that a single functional complex does not constitute the majority of all the characters being used (otherwise, true phylogenetic affinities will be obscured by taxa that have evolved convergently with respect to the functional complex in question). After characters have been properly analyzed, cladograms (phylogenetic trees) are constructed using a variety of computer programs which have been developed for this purpose.