Date of Award


Degree Name

Master of Arts


Biological Sciences

First Advisor

Dr. Richard Pippen

Second Advisor

Dr. Cecil McIntire

Access Setting

Masters Thesis-Open Access


Three groups of the common shiner (Notropis cornutus, Mitchell) were adapted to three different photoperiods. These photoperiods were 16L:8D (summer), 12L:12D (controls), and 8L:16D (winter). The prolactin cells were studied histologically and morphologically with respect to staining characteristics, cell and nuclear morphology, nuclear size, and cellular density. The prolactin cells of those fish under the long photoperiod exhibited greater cellular activity than the controls as evidenced by an increase in nuclear size, cellular density, and by becoming more circular. The prolactin cells of those fish under the short photoperiod exhibited the same characteristics as those in the long photoperiod. The staining characteristics did not vary between photoperiods. The results indicate that prolactin synthesis and secretion may be under seasonal control.