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

First published online March 2, 2007
Journal of Experimental Biology 210, 983-992 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02732

This Article Summary 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 Donini, A. Articles by O'Donnell, M. J. Search for Related Content PubMed PubMed Citation Articles by Donini, A. Articles by O'Donnell, M. J.

Changing salinity induces alterations in hemolymph ion concentrations and Na⁺ and Cl^– transport kinetics of the anal papillae in the larval mosquito, Aedes aegypti

Andrew Donini^*, Mandeep P. Gaidhu, Dana R. Strasberg and Michael J. O'Donnell

Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada

View larger version (17K): [in this window] [in a new window]   Fig. 1. Transfer of mosquito larvae from freshwater (FW) to 30%SW (seawater) leads to significant increases in Na+, Cl– and H+ concentrations in the hemolymph within 5 h of transfer. Groups of mosquito larvae were transferred from FW to 30%SW at time=0, where they were held for varying periods of time prior to the collection of hemolymph. Ion-selective microelectrodes were used to measure the Na+ (A), Cl– (B), K+ (C) and H+ (D) ion concentrations of the hemolymph. Values are means ± s.e.m., N=16 for time=0 and N=10 for all other groups. An asterisk denotes a significant difference from value at time=0.

View larger version (16K): [in this window] [in a new window]   Fig. 2. Transfer of mosquito larvae from 30%SW (seawater) to FW (freshwater) results in significant decreases of Na+, Cl– and H+ concentrations in the hemolymph within 6 h of transfer. Groups of mosquito larvae that were reared in FW were transferred and held in 30%SW for at least 24 h. Larvae were subsequently transferred back to FW at time=0, where they were held for varying periods of time prior to the collection of hemolymph. Ion-selective microelectrodes were used to measure the Na+ (A), Cl– (B), K+ (C) and H+ (D) ion concentrations of the hemolymph. Values are means ± s.e.m., N=6–14. An asterisk denotes a significant difference from value at time=0.

View larger version (10K): [in this window] [in a new window]   Fig. 3. Potassium cyanide significantly reduces Na+ uptake by anal papillae of mosquito larvae. Na+ concentration gradients at a single point adjacent the surface of isolated (in vitro) anal papillae were measured using the SIET system in a 1 mmol l–1 Na+ bath. After a minimum of 40 min, 30 µmol l–1 KCN was added to the bath. Results are shown as Na+ flux. (A) A representative preparation illustrates the time course of KCN effects on Na+ influx. Influx remained consistent for 45 min. KCN was added at the vertical broken line and Na+ influx immediately decreased and was abolished in 6 min. (B) Na+ influx measured immediately after the preparation was set up (initial), 1 min prior to the addition of KCN (30–45 min) and 5 min after the addition of KCN. Values are mean ± s.e.m. of seven individual papillae. The asterisk denotes a statistically significant difference from the initial measurements.

View larger version (28K): [in this window] [in a new window]   Fig. 4. Exposure to 30%SW significantly changes the Michealis–Menten kinetics of Na+ and Cl– influx at the papillae. Na+ or Cl– influx was calculated using the measurements obtained from the SIET system from a single point on the surface of the anal papillae while changing the bath NaCl concentration. The results obtained from each individual papilla were fitted to the Michaelis–Menten equation using non-linear regression analysis. Jmax, maximum rate of transport; Kt, Na+ or Cl– concentration that yields a flux of 50% Jmax. (A) Na+ and (B) Cl– influx from single papillae obtained from larvae maintained in FW (freshwater; squares) or in 30%SW (seawater) for 5 h (triangles). (C) Kt and (D) Jmax (means ± s.e.m.) for groups of papillae obtained from larvae that were either held in freshwater (FW), had been transferred from FW to 30%SW for 5 h (30%SW), or were held in 30%SW for 5 h and subsequently transferred to FW (30%SW/FW) for 20 h (Na+, white bars, N=6–13) or 5 h (Cl–, black bars, N=8–13). An asterisk denotes a statistically significant difference from the FW group. Kinetic parameters for Na+ (N=6) and Cl– (N=5) uptake by the papillae of intact larvae (in vivo) held in FW are also shown (no difference from FW, t-test, P<0.05).