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

This Article 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 Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by WHEATLY, M. G. Articles by IGNASZEWSKI, L. A. Search for Related Content PubMed Articles by WHEATLY, M. G. Articles by IGNASZEWSKI, L. A.

Journal of Experimental Biology 151,469-483 (1990)
Published by Company of Biologists 1990

Electrolyte and Gas Exchange during the Moulting Cycle of a Freshwater Crayfish

MICHELE G. WHEATLY ¹ and LORI A. IGNASZEWSKI ²

¹ Department of Zoology, University of Florida Gainesville, FL 32611, USA
² Department of Medical Sciences, College of Veterinary Medicine, University of Florida Gainesville, FL 32611, USA

Whole-animal net electrolyte fluxes (Ca²⁺, apparent H⁺ , titratable acidic equivalents, ammonia, Na⁺, Cl^-, K⁺, Mg²⁺, phosphate and sulphate) and respiratory gas exchange were monitored throughout the moulting cycle in juvenile freshwater crayfish Procambarus clarkii (Girard) at 21 °C. Intermoult crayfish were essentially in ion balance. As crayfish approached ecdysis (-3 days, where t=0 is the day when the cuticle is shed), there was a net efflux of Ca²⁺ (-1000µmolkg^-1 h^-1) correlated with a corresponding uptake of acidic equivalents (or base output) of +2000µmolkg^-1 h^-1. Following ecdysis, both fluxes switched vector; uptake of Ca^2- (+2000µmolkg^- h^-) and basic equivalents (+4000µmolkg^-1h^-1) were completed within 6 days. The moulting cycle also affected fluxes of electrolytes other than those involved in CaCO₃ resorption and deposition. Crayfish remained in Na⁺; and C^-; balance from intermoult up to ecdysis. Following ecdysis, both were taken up actively at rates of around plus;500µanolkg^-1h^-1 for 3 days, presumably restoring the haemodilution that would have resulted from water loading. A premoult efflux of K⁺ was partially offset by postmoult uptake. Meanwhile, crayfish experienced increased efflux of phosphate following ecdysis, probably because of increased integumentary permeability. Rates of O₂ uptake (MO₂) and CO₂ excretion (Mco₂) increased to peak values (double intermoult rates) immediately prior to ecdysis. While MO₂ recovered during postmoult, Mco₂ dropped precipitously, significantly reducing the gas exchange ratio. Since the Mco₂ deficit agreed well with the postmoult basic equivalent uptake, the latter is probably attributable to HCO₃^- uptake for calcification.

Key words: crayfish, moulting, calcium, acid-base balance

Accepted on March 29, 1990