Beth Glidewell

 

My research consists of examining the possibility of sexual dimorphism in convict cichlid fish. The potential differences between males and females (size, shape, and color) can be observed systematically by using geometric morphometrics. This is a way of examining the exact measurements and specific points on an individual fish and calculating how different the sexes (as a group) are from each other. By seeing how the different points relate to each other, we can calculate a graph of average male and female fish to note any consistent differentiation between the sexes.

 

To do the math and calculations, first we need data from the fish. We obtain that by placing fish into a small, clear, water-filled box and photographing them from the side. To keep note of scale, a ruler is placed in view at all times. The digital photographs are then entered into a computer program where I can mark my predetermined points of reference. The program will analyze the data digitally and create graphic representations of the data.

In order to determine which fish are females and which are male, it is necessary to breed them. This is done by pairing what I can guess are a single female fish with a single male fish. The pair is observed and photographed every four days (on average) until one of several events may occur. If the fish breed (eggs that hatch into wrigglers), then I have a successful pair, and one male and one female to use in my research. If, however, they fail to breed or produce eggs that do not hatch, then they are unusable and their photographs are discarded. There have also been instances where one fish kills another. The remaining fish will first be paired with another to attempt breeding, or if it is especially aggressive, then it will not be used at all.

 

CSUS BIO SCI