Meeting Abstract

P3.114  Jan. 6  Diapause and metabolic cost of overwintering for Eurosta solidaginis during an unusually mild winter BENNETT, V.A.**; SKINNER, E.C.; PERRY, K.M.; DORSEY, K.M.; Clarion University of Pennsylvania vbennett@clarion.edu

Low temperatures of winter place stress on many organisms, however, mild winter temperatures may also be problematic. Freeze-tolerant Eurosta solidaginis larvae overwinter in galls on the stems of goldenrod plants where they are exposed to the extremes of winter temperatures. Eurosta enter diapause, a dormant state characterized by reduced metabolism and arrested morphological development, each winter, allowing them to conserve energy and synchronize spring reproduction. Larvae were collected at various times during the 2005-06 season and metabolic rates were measured to determine the length of time spent in diapause in Western Pennsylvania. By 21 October 2005, larval metabolic rates were low at all temperatures, and no larvae pupated when exposed to spring conditions, indicating that Eurosta had already entered diapause. Metabolic rates remained low in larvae collected in January and February 2006, but began to increase in larvae collected 8 March 2006. Most of these larvae pupated within 7 days of exposure to spring conditions indicating emergence from diapause. Supercooling points and survival of freezing treatments indicated that larvae remained freeze-tolerant. Although Eurosta experienced a series of freeze-thaw events during the first week of March, there were few freezing episodes during this unusually mild winter. Metabolic rates of diapausing larvae were measured at several temperatures, and a mathematical model was determined to calculate the energetic cost of overwintering based on recorded field temperatures. Metabolic cost was greater for the mild 2005-06 winter when compared to that for the more typical 2004-05 winter.