(full paper is archived in the Miller Library)
Title: Thermal dependence of feeding and absolute feeding rates of a northern-occurring (Nucella ostrina) and a southern-occurring (N.emarginata) rocky intertidal whelk
Student Author(s): Jhawar, Kam
Faculty Advisor(s): Somero, George
Location: Final papers Biology 175/176H
Date: June 2003
Keywords: In this study, I examined predation by two species of whelk on bay mussels (Mytilis trossulus) to determine whether a northern-occurring species (Nucella ostrina) and a southern-occurring species (Nucella emarginata) differed in thermal dependence of feeding and in absolute feeding rate. Each species was held in three temperature treatments: 21oC, 14-16oC (ambient), and 10.5oC for 28 days. Feeding by both species displayed classical physiological responses to temperature (Q10 = 2) for the first 14 days. By the twenty-first day, when satiation seemed to occur, Q10 values increased to 4.49 and 5.35 for N. emarginata and N. ostrina, respectively. In particular, both species at 10oC demonstrated considerably reduced feeding rates upon satiation. This suggests that metabolic costs were much lower at 10oC and, therefore, the animals required less energy input after satiation. While N. ostrina’s Q10 value declined to 1.67 after an additional 7 days, N. emarginata’s Q10 value declined to 3.40. Across all temperatures, N. emarginata usually had higher feeding rates for the first 14 days, but, after 21 and 28 days, N. ostrina tended to have higher feeding rates. Total consumption rates for the entire experimental period were not significantly different between species at any temperature. These results suggest that, while N. ostrina feeding rates may be lower after a starvation period, N. ostrina is able to maintain similar levels of energy input over the long-term by having a shorter satiation phase. For both species, feeding rates will be discussed with regard to O2 consumption rates.