Date of Award


Degree Name

Biological Sciences


College of Science

Type of Degree


Document Type


First Advisor

Jeff Kovatch

Second Advisor

Brian Antonsen

Third Advisor

Anne Axel


Ecological niche theory suggests two species cannot live in the same ecological niche and differences should exist among species that appear to cohabitate. Variations in physiology and behavior that potentially enable species coexistence can be reflected in metabolism. This study investigated coexisting darter fishes by measuring the metabolism of greenside (Etheostoma blennioides) and variegate (E. variatum) darters over 48 h using intermittent-flow respirometry. Activity was analyzed using time-lapse videos. E. blennioides mean metabolic rate (154.64 ± SE 52.54 mg O2·kg-1 ·hr-1 ; n=14; p=0.0006) was significantly greater than and varied more than E. variatum’s mean rate (92.51 ± SE 32.70 mg O2·kg-1 ·hr-1 ; n=15). E. blennioides had consistently elevated activity compared to E. variatum, but was not significantly different over time (F1,4=3.24, p=0.5173); while E. variatum’s activity was (F1,4=20.50, p=0.0004). The results may suggest that E. blennioides is a bolder, more active species than E. variatum. Physiological and behavioral differences revealed between E. blennioides and E. variatum could potentially explain their coexistence. Second, a comparison of published studies on darter metabolism was conducted to elucidate interspecific variation among a greater number of darter species. This search resulted in metabolic data on a total of 11 darter species, which were compared to the current study in three ways (using the 48 h mean rates, the first 4.5 h mean rates, and the middle 24 h mean rates). The results showed interspecific variation in metabolic rates among darters, but also illustrated the importance of developing methods that measure metabolism accurately. Finally, this study helped uncover differences among darters using a physiological approach and will hopefully lead to an increased interest in quantitative darter physiological ecology.


Darters (Fishes) -- Ecology.