Meeting Abstract

P2.22  Friday, Jan. 4  Supercooling point of Eurosta solidaginis: demographic profile and effect of repeat freeze exposure. ROBICH, Sarah R.*; LAYNE, JR., Jack R.; Slippery Rock Univ., PA; Slippery Rock Univ., PA srr0884@sru.edu

As part of their preparation for overwintering, freeze-tolerant larvae of the dipteran Eurosta solidaginis elevate their supercooling point (SCP) by 5 � 10 C over the course of the autumn. It was recently shown that freeze-tolerant larvae of another dipteran, Syrphus ribesii, have markedly reduced SCPs following exposure to freeze events. Our study examined the effect of recent freeze exposure on SCP and the demographic profile of SCPs in Eurosta larvae. Goldenrod ball galls containing larvae were collected in Butler County, PA in early November. The larvae were kept at 3 C for 8 weeks and then were removed from the galls. They were subsequently cooled at a rate of 0.5 C/min until the onset of freezing occurred. The SCPs were then retested 1 h, 2 d, and 5 d later. Linear regression revealed that the SCP was not dependent on body mass (N = 56, P = 0.6481). The initial SCP values (-9.8 + 0.6 C) of larvae had a negatively skewed distribution (D�Agostino normality test, P < 0.0001). These results support the notion that potent ice nucleators are present in these larvae. The 2 d retest revealed a small but significant rise in SCP (-10.0 + 0.8 C to -9.2 � 1.4 C; Wilcoxon sign test, P = 0.0039) that did not happen with the 1 h (Wilcoxon sign test, P = 0.5625) and 5 d retests (Wilcoxon sign test, P = 0.1876). Our findings indicate that the SCP of E. solidaginis larvae are temporarily adjusted upward after a freeze event, which may be advantageous to larvae during periods of rising and falling temperatures in the winter by reducing their time spent supercooled.