QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online May 5, 2005
Journal of Experimental Biology 208, 1895-1904 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01596

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Yi, S.-X. Articles by Lee, R. E. Search for Related Content PubMed PubMed Citation Articles by Yi, S.-X. Articles by Lee, R. E., Jr

Changes in gut and Malpighian tubule transport during seasonal acclimatization and freezing in the gall fly Eurosta solidaginis

Shu-Xia Yi and Richard E. Lee, Jr^*

Department of Zoology, Miami University, Oxford, Ohio 45056, USA

Author for correspondence (e-mail: leere{at}muohio.edu)

Accepted 14 March 2005

Since few studies have examined cold tolerance at the organ level in insects, our primary objective was to characterize the functional responses of the gut and Malpighian tubules (MT) to seasonal acclimatization, chilling and freezing in larvae of the goldenrod gall fly Eurosta solidaginis Fitch (Diptera, Tephritidae). From September to December, hemolymph osmolality (455-926 mOsmol kg l^-1) and freezing tolerance increased markedly in field-collected larvae. Chlorophenol Red was readily transported into the lumen of the foregut, the posterior portion of the midgut, the ureter, the proximal region of the anterior pair of MT, and entire posterior pair of MT. Ouabain and KCN inhibited transport of Chlorophenol Red in the gut and MT. Transport was readily detected at 0°C and the rate of transport was directly related to temperature. The rate of fluid transport by the MT decreased steadily from a monthly high in September (10.7±0.8 nl min^-1 for the anterior pair; 12.7±1.0 nl min^-1 for the posterior pair) until secretion was no longer detectable in December; this decrease parallels entry into diapause for this species. Even in larvae that died following freezing for 40 days at -20°C, individual organ function was retained to a limited extent. Through the autumn, cholesterol concentrations in the hemolymph increased nearly fourfold. In contrast, the ratio of cholesterol to protein content (nmol mg l^-1) in the MT membrane remained relatively constant (2224 nmol mg l^-1 protein) during this period. Freezing of larvae for 20 days at -20°C caused a significant decrease in cholesterol levels in the hemolymph and the MT membranes compared to unfrozen controls. These results suggest that cholesterol plays a role in seasonal cold hardening and freeze tolerance in insects.

Key words: transport, cholesterol, epithelial membranes, freezing tolerance, cold tolerance, Malpighian tubule, gall fly, Eurosta solidaginis