Summary
Moulting fluid ofManduca sexta contains high concentrations of potassium and bicarbonate (100 mM) and low concentrations of chloride (5 mM). This fluid begins to disappear from the exuvial space approximately 9–10 h before the actual shedding of the integument. During this time, the integument can be isolated in an Ussing cell and electrical properties measured in vitro. In a normal 32 mM KHCO3 saline, potential difference (PD) is around 10 mV, exuvial side positive, and short-circuit current (SCC) is 15–20 μA cm−2. Substitution of chloride slightly reduces both PD and SCC, although resistance does not change significantly. Measurement of chloride transport in the absence of K+ indicates that 100% of the SCC can be accounted for by the net chloride flux (∼2 μA cm−2). TheK m andJ max for transepithelial chloride transport are 14 mM and 0.1 μEq cm−2 h−1. Bilateral potassium addition stimulates chloride transport, doubling net chloride flux as potassium concentration increases from 2 to 5 mM. Chloride net flux is not inhibited by the presence of furosemide (1 mM), nor in HCO −3 -free saline by thiocyanate (1 or 10 mM) or acetazolamide (0.1 mM), but is inhibited by 100% N2. The pattern of chloride transport inM. sexta is similar to that previously reported for the rectum of locusts. As chloride is normally at low concentrations in the moulting fluid, it is suggested that this transport system acts to maintain low intracellular concentrations which may be necessary for enzymatic functions in the epidermal cells and has little importance in fluid transport.
Similar content being viewed by others
Abbreviations
- PD :
-
potential difference
- PPI :
-
pharate pupal integument
- SCC :
-
short circuit current
References
Bell RA, Joachim FG (1976) Techniques for rearing laboratory colonies of tobacco hornworms and pink bollworms. Ann Entomol Soc 69:363–373
Cooper PD, Deaton LE, Jungreis AM (1980a) Chloride transport during resorption of moulting fluid across the pharate pupal integument of tobacco hornworms,Manduca sexta. J Gen Physiol 76:9a
Cooper PD, Deaton LE, Jungreis AM (1980b) Role of K+ in maintenance of the transmural potential and short circuit current across the pharate pupal integument during resorption of moulting fluid. Physiologist 23:170
Cooper PD, Jungreis AM (1980) Chloride transportation across the integumentary epithelium in the sphyngid moth,Manduca sexta. Am Zool 20:736
Cornell JC, Pan ML (1982) Tobacco hornworms,Manduca sexta, drink molting fluid before the larval-pupal molt. Am Zool 22:913
Cornell JC, Jungreis AM (1983) Potassium transport in the isolated pharate pupal integument of the tobacco hornworm,Manduca sexta. J Comp Physiol 153:147–157
Deaton LE (1984) Tissue K+-stimulated ATPase and HCO −3 -stimulated ATPase in the tobacco hornworm,Manduca sexta. Insect Biochem 14:109–114
Frizzell RA, Field M, Schultz SG (1979) Sodium-coupled chloride transport by epithelial tissues. Am J Physiol 236:F1-F8
Hanrahan JW, Phillips JE (1982) Electrogenic, K+-dependent chloride transport in locust hindgut. Phil Trans R Soc Lond B 299:585–595
Hanrahan J, Phillips JE (1983) Mechanism and control of salt absorption in locust rectum. Am J Physiol 244:R131-R142
Hanrahan JW, Phillips JE (1984a) KCl transport across an insect epithelium: I. Tracer fluxes and the effects of ion substitutions. J Membr Biol 80:15–26
Hanrahan JW, Phillips JE (1984b) KCl transport across an insect epithelium: II. Electrochemical potentials and electrophysiology. J. Membr Biol 80:27–47
Johnston JW (1979) Carbonic anhydrase and bicarbonate regulation during the larval-pupal transformation of the tobacco hornworm (Manduca sexta) and the silkworm (Hyalophora cecropia). PhD thesis, University of Tennessee, Knoxville
Johnston JW, Jungreis AM (1981) Carbonic anhydrase activity during the larval-pupal transformation ofHyalophora cecropia reared on foliage and synthetic diet: Effects of potassium and chloride on midgut, fat body and integumentary enzymes. J Exp Biol 91:255–269
Jungreis AM (1978) The composition of larval-pupal moulting fluid in the tobacco hornworm,Manduca sexta. J Insect Physiol 24:65–73
Jungreis AM (1979) Physiology of moulting in insects. Adv Insect Physiol 14:109–183
Jungreis AM, Harvey WR (1975) Role of active potassium transport by integumentary epithelium in secretion of larvalpupal moulting fluid during silkmoth development. J Exp Biol 62:357–366
Jungreis AM, Barron ND, Johnston JW (1981) Comparative properties of tobacco hornworm,Manduca sexta, carbonic anhydrases. Am J Physiol 241:R92-R99
Jungreis AM, Ruhoy M, Cooper PD (1982) Why don't tobacco hornworms,Manduca sexta L. (Lepidoptera: Sphyngidae) become dehydrated during larval to pupal and pupal to adult development. J Exp Zool 222:265–276
Locke M, Smith DS (1980) Insect biology in the future. Academic Press, New York
Nijhout, JF (1974) Control of moulting and metamorphosis in the tobacco hornworm,Manduca sexta L.: Growth of the last instar larva and the decision to pupate. J Exp Biol 61:481–492
Pan ML, Cornell JC (1982) Do lepidopterans drink molting fluid before the pupal-adult molt? Am Zool 22:913
Phillips JE (1980) Epithelial transport and control in recta of terrestrial insects. In: Locke M, Smith DS (eds) Insect biology in the future. Academic Press, New York, pp 145–177
Phillips JE, Hanrahan JW (1984) Chloride transport in insects: A novel K-stimulated, electrogenic pump. In: Gerencser GA (ed) Chloride transport coupling in biological membranes and epithelia. Elsevier Science Publishers, New York, pp 151–181
Reynolds SE (1981) Integration of behaviour and physiology in ecdysis. Adv Insect Physiol 16:475–595
Strange K, Phillips JE, Quamme GA (1984) Mechanisms of CO2 transport in rectal salt gland ofAedes II. Site of Cl−−HCO −3 exchange. Am J Physiol 246:R735-R740
Williams D, Phillips JE, Prince WT, Meredith J (1978) The source of short circuit current across locust rectum. J Exp Biol 77:107–122
Williams-Boyce PK, Jungreis AM (1980) The larval-pupal transformation ofManduca sexta: Changes in body and tissue weights and tissue hemolymph adherence. Ann Entomol Soc Am 73:602–608
Wood JL (1972) Some aspects of active potassium transport by the midgut of the silkworm,Antheraea pernyi. Ph D thesis, Cambridge University
Wood JL, Moreton RB (1978) Refinements in the short-circuit technique and its application to active potassium transport. J Exp Biol 77:123–140
Author information
Authors and Affiliations
Additional information
In the time since this research was performed, A.M. Jungreis passed away. He will be missed by his friends and colleagues
Rights and permissions
About this article
Cite this article
Cooper, P.D., Jungreis, A.M. Chloride transport across the integumentary epithelium ofManduca sexta (Lepidoptera: Sphingidae). J Comp Physiol B 155, 743–750 (1985). https://doi.org/10.1007/BF00694589
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00694589