Neurohormonal Integration of Osmotic and Ionic Regulation 1

Transcription

1 AMER. ZOOL., 25: (1985) Neurohormonal Integration of Osmotic and Ionic Regulation 1 LINDA H. MANTEL Department of Biology, City College, New York, New York SYNOPSIS. There is evidence in crustaceans that neuroendocrine centers, including the eyestalk, brain, thoracic ganglionic mass, and pericardial organ, produce factors that affect osmotic and ionic regulation. Understanding of the processes responsible for osmotic adjustment in the intact animal, such as regulation of permeability, active uptake of ions, and respiratory and cardiovascular alterations, has increased substantially in the past few years. However, interaction of neuroendocrine factors with the target tissues and systems is just beginning to be investigated. There is evidence that content of lipids and activity of enzymes are important in osmoregulation, and neuroendocrine effects on these metabolic processes are worthy of study. In addition, there are some crustaceans in which osmoregulatory ability varies developmentally. Further investigations of such animals is also necessary. Progress in our understanding of neuroendocrine influences on osmoregulation depends upon further purification of active factors from neuroendocrine centers and hemolymph, and upon development of appropriate assays on which to test them. INTRODUCTION The topic of neuroendocrine regulation of salt and water balance in crustaceans was last reviewed for readers of American Zoologist by Kamemoto in In the intervening years, only about 20 studies, including both published papers and unpublished theses, have been carried out that relate directly to neuroendocrine influence on osmotic and ionic regulation. Some of these were briefly mentioned in the more recent reviews by Kamemoto and Oyama (1984) and by Mantel and Farmer (1983). This relatively small increase in our knowledge contrasts greatly with the steady growth of information on crustacean osmoregulation and neuroendocrine systems perse, and with the understanding of hormonal effects on osmoregulatory systems in the "nearest neighbors" of crustaceans, the insects and fishes. Why has progress been so slow? Crustacean systems present problems perhaps more extensive than those in fishes or insects. Variability of animals in vivo in response to experimental manipulations; the pervasive influence of the molt cycle; the paucity of good in vitro systems; our dependence on a few "specialist" animals; and just not having come upon the right 1 From the Symposium on Advances in Crustacean Endocrinology presented at the Annual Meeting of the American Society of Zoologists, December 1983, at Philadelphia, Pennsylvania. 253 system yet all these conspire to reduce the rate of increase of knowledge. My goal in this review is to provide the framework within which our questions are asked; to present briefly the physiological mechanisms involved in osmoregulation; to mention some recent studies that provide tantalizing evidence for neuroendocrine influence on these mechanisms; and to goad the crustacean transport and systems control specialists to form new hypotheses for testing. OSMOREGULATORY PROCESSES Patterns of regulation and basic physiological mechanisms The variety of osmoregulatory patterns exhibited by crustaceans and shown in Figure 1 presents immediately the crucial questions: how are these responses brought about (i.e., what are the mechanisms involved); and why are the patterns so variable? What are the major differences between a conformer and a regulator? Does an osmoconformer lack the tissue-based mechanisms, or does it lack the control system to turn them on? The major mechanisms for osmotic and ionic regulation include control of passive permeability to water and ions at the boundary surfaces (gill, gut, antennal gland), and active uptake and excretion of ions across these same boundaries. For instance, a crustacean exposed to sea water more dilute than its hemolymph is faced

2 254 LINDA H. MANTEL o n o _400 OsmolalKy of Medium (mostn) FIG. 1. Some patterns of osmoregulation in brackish-water and marine decapod crustaceans. Solid diagonal line indicates an isosmotic relationship between hemolymph and medium. (1) Euryhaline osmoconformer, e.g., Panulirus longipes. (2) Stenohaline osmoregulator, e.g., Trachypenaeussimilis. (3) Strong hyper- and hyporegulator, e.g., Crangon crangon. (4) Isosmotic at high salinities, strong hyperregulator at low salinities, e.g., Callinectes sapidus. (5) Isosmotic at high salinities, weak hyperregulator at low salinities, e.g., Cancer magister. (6) Moderate hyper- and hyporegulator, e.g., Pachygrapsus crassipes. (From Mantel and Farmer, Reprinted with permission.) 1000 I 1200 I with a gain of water and loss of salts by diffusion. These problems may be minimized by a reduction in permeability to water and ions, but compensatory uptake of ions is also necessary to maintain steadystate balance. For animals that are osmoregulators, this compensatory uptake must also be great enough to allow the animals to maintain their hemolymph hyperosmotic to the medium. Permeability. Permeability is a factor that differentiates between regulators and con-

3 formers. In general, permeability both to ions and to water is higher in conformers than in regulators. In addition, many osmoregulators show a decrease in permeability upon transfer to a dilute medium (Smith, 1967, 1970; Hannan and Evans, 1973; Berlind and Kamemoto, 1977). Mechanisms for this decrease in permeability may include, in addition to alterations in the boundary tissues themselves, changes in the rate of blood flow through the gills, shunt pathways in the gills that regulate exposure of hemolymph to the dilute medium, changes in ventilation rate and heart rate, and changes in flow of water over the gills. Smith coined the term "apparent permeability" to indicate the changes in rate of entry or exit of water or ions that could be measured in the whole animal under different conditions, without postulating a particular mechanism as the one responsible. In Sphaeroma serratum, Thuet (1978) has found, as expected, that fluxes of water are 3-4 times greater in animals in sea water than those in 50% sea water. When the animals are directly transferred from full strength to dilute sea water, the fluxes are "instantaneously and entirely reset" decreases in permeability occur within 30 sec of transfer. The effect is also instantaneous in the other direction. The presence of Na and Cl of appropriate concentration, rather than the total osmotic pressure, seems to be responsible for setting the level of permeability. What is the mechanism for resetting? There are no significant differences in heart rate or changes in blood flow in S. serratum during these transfers. In fact, as is often the case, oxygen consuption increases when the animals are in dilute sea water. Somehow there seems to be a direct reduction in permeability of the exchange membranes themselves, perhaps related to changes in microfilaments and microvilli of the apical surface. Comparisons of 5. serratum with Gammarus duebeni show that the latter also instantly reduces its permeability when switched from full to dilute sea water, but that 16 hr are required for the reverse change. In the crab Rhithropanopeus harrisii, 6 hr are required for a reduction in NEUROHORMONES AND OSMOREGULATION 255 permeability and 12 hr for the increase on return to full sea water. S. serratum is the only animal known that can adjust instantaneously in both directions. Some of these changes in permeability can also be found in isolated tissues. Cantelmo (1976,1977) found that both gill and gut of the crabs Callinectes sapidus and Cancer irroratus had a lower permeability to tritiated water when taken from animals acclimated to 50% sea water than from animals acclimated to 100% sea water. These changes may result from biochemical alterations, particularly in content and types of lipid present in gills and other tissues. Chapelle et al. (1976, 1977) found that phospholipids in the gills of Eriocheir sinensis increase in concentration when the crabs are acclimated to fresh water; similar effects are seen in C. sapidus in dilute sea water, but not in the osmoconformer Libinia emarginata (Whitney, 1974). The only study that has combined an investigation of permeability and lipid content in the same animals is that of Morris et al. (1982) in the euryhaline amphipod Gammarus duebeni. They acclimated the animals to either 2% or 100% sea water for 60 days. As is the case in decapods, there was a decrease in permeability to water after the animals were exposed to 2% sea water. However, in contrast to the crabs just mentioned, there was no difference in the phospholipid content of gills from animals at the different salinities. However, concentratidn of saturated fatty acids in the phospholipids was higher in animals acclimated to dilute sea water than in those acclimated to full sea water. What could be the adaptive significance of these changes in lipids? In many poikilotherms, adaptation to high temperature causes both an increase in phospholipid content and an increase in saturated fatty acids. Both of these may change fluidity of membranes and perhaps alter permeability. Thus where decapods may compensate for low salinity by increasing phospholipid concentration, amphipods may accomplish the same effect by increased saturation of their fatty acids. Clearly, further careful work correlating permeability of the animal and the gills with lipid composition of the gills and other

4 256 LINDA H. MANTEL WATER GILL BLOOD HCO,- + H* CO, CO NH 4 4 H' + NH, 4 Fie. 2. A model of possible ionic fluxes in the osmoregulating blue crab. Dashed lines represent movements by diffusion; solid lines represent some form of coupled transport. Large arrows show predominant direction of reactions. (From Henry and Cameron, Reprinted with permission.) tissues could be most useful for providing understanding of mechanisms. Active uptake. The structural and enzymatic characteristics of salt uptake have become clarified in recent years, although a definitive model for the process is still not available. In tissues such as gill, transport of ions normally is brought about by cells exhibiting a typical "salt-transporting" morphology of apical channels or infoldings, forming a large subcuticular space, and a highly infolded baso-lateral membrane surface in close contact with many mitochondria (Copeland and Fitzjarrell, 1968; Mantel and Farmer, 1983; Barra etal., 1983). Associated with this morphology are important enzymatic activities, notably Na + K-activated ATPase and carbonic anhydrase (CA). The ATPase has been shown in many cases to increase its activity when an osmoregulator is placed into a dilute medium, although the correlation between enzymatic activity and salinity of acclimation is not absolute (Mantel and Farmer, 1983; Towle, 1984a,6). Both Na + and NH + 4 can serve as counter-ions for the enzyme. There is also an HCO 3 ~-Cl~-activated ATPase, but its function is not so clearly related to salinity of acclimation (DePew and Towle, 1979). Recent studies with vesicles isolated from baso-lateral membranes of gills of Callinectes sapidus and Carcinus maenas have demonstrated ATPdependent uptake of Na + associated with Na + K-ATPase activity (Towle et al.,1983). Carbonic anhydrase is localized in the cytoplasm. In C. sapidus that is osmoregulating in dilute medium, inhibition of this enzyme by acetazolamide causes Na + and Cl" content of the hemolymph (blood) to decrease. The enzyme probably functions by providing HCO 3 ~ and H + as counter-ions for ATPases. A model incorporating these features is shown in Figure 2 (Henry and Cameron, 1983). Respiratory and circulatory systems. In his review in 1976, Kamemoto suggested that one avenue of future research should "explore the possible interrelationships of the activity of the heart and blood circulation, the respiratory mechanism, and

5 NEUROHORMONES AND OSMOREGULATION 257 RES FIG. 3. Diagrammatic composite decapod crustacean indicating neuroendocrine centers (1-4) and osmoregulatory tissues (5-9). Documented examples in which extracts of neuroendocrine centers have effects on the target tissues are indicated with arrows. (1) Eyestalk system (ES). (2) Brain (B). (3) Thoracic ganglionic mass (ThG). (4) Pericardial organ (PO). (5) Proventriculus. (6) Intestine. (7) Gill. (8) Antenna! gland. (9) Heart. (Redrawn from Kamemoto, Used with permission.) osmoregulation." So far, few of us have stepped forth to take up the challenge. Hume and Berlind (1976) found that when specimens of Carcinus maenas were transferred from 100% sea water to 15% sea water, the heart rate increased markedly; in some cases the rate of scaphognathite beating decreased simultaneously. Without direct measurements, it is difficult to determine whether the rate of blood flow across the gills would increase or decrease under these conditions, and thus how this response could be related to a change in permeability. Gill perfusion may be increased by an increased rate of scaphognathite pumping, because of expansion of the gill lamellae (McMahon and Wilkens, 1983). However, our understanding of the pathways of blood flow through the gills is still so rudimentary that conclusions cannot be drawn on the effects of changes in heart rate and ventilation on permeability. EFFECTS OF NEUROENDOCRINES ON OSMOREGULATORY SYSTEMS What is the relationship of neuroendocrine systems to the mechanisms of osmoregulation just discussed? In essence, there is evidence to date that extracts of various neuroendocrine tissues, including the sinus gland of the eyestalk, the brain, the thoracic ganglionic mass, and the pericardial organ, can affect fluxes of water and ions in an intact animal and across the membranes of the regulatory tissues. A summary of these sites and effects is shown in Figure 3. So far, no substances directly involved in osmoregulation have been identified or purified from the brain, eyestalk complex, or major thoracic or ventral ganglia. However, the pericardial organ (PO) is known to contain two peptides and three amines (serotonin, dopamine, and octopamine) which have effects on the respiratory and circulatory system and on

6 258 LINDA H. MANTEL uptake of ions by crayfish (Kamemoto and Tullis, 1972; Cooke and Sullivan, 1982). Evidence in intact animals Evidence for neuroendocrine control of osmoregulation is provided in vivo from experiments involving ligation or removal of eyestalks followed by monitoring osmolality of hemolymph and urine, rate of urine flow, or gain of weight at molt. Depending on the system and animal under investigation, removal of eyestalk factors from circulation can result in increased or decreased osmotic concentration, increased or decreased rate of urine flow or no effects at all. In most cases, effects seen upon removal of eyestalks can be reversed by injection of eyestalk extracts (Kamemoto, 1976; Heit and Fingerman, 1975; Holliday, 1978; De Leersnyder, 1967; Muramoto, 1981). Other in vivo experiments show that extracts of brain or thoracic ganglionic mass (TGM) may also reverse effects of eyestalk removal. Brain extracts can increase osmolality of the hemolymph of destalked fiddler crabs (Davis, 1978), and increase rate of urine flow in destalked Cancer magister or Carcinus maenas (Holliday, 1978; Norfolk, 1978). Implantation of TGM into destalked Gecarcinus lateralis can affect distribution of water at ecdysis (Bliss, 1968; Mantel et al, 1975). In addition, injections of TGM extracts can either increase or decrease fluxes of water into Thalamita crenata, depending on whether the extracts are water- or acetone-soluble (Kamemoto and Tullis, 1972; Tullis and Kamemoto, 1974). Although these results are of interest and important, it is difficult to provide an explanation of mechanism, since the effects noted may be brought about by a number of processes occurring at various sites. In contrast to some previous studies, recent experiments with intact animals have concentrated on removal of neuroendocrine structures and replacement with tissues from the same animal. In the freshwater prawn Caridina weberi, removal of eyestalks causes a drop in body weight and an increase in Cl~ concentration of hemolymph when compared to controls. However, blocking the nephropores after eyestalk ablation caused experimental animals to increase in weight more than controls. Thus the removal of eyestalks seemingly caused a diuresis, meaning that an antidiuretic hormone is present in the eyestalks. Diuresis often results from increased uptake of water over permeable surfaces. Injection of eyestalk extracts reversed the effects, as expected. Other possible sources of this active substance are likely, since injection of brain and TGM both increased blood Cl" in destalked shrimp, with brains being the more potent. These results are in all respects similar to those found by Kamemoto and co-workers on crayfish (Nagabhushanam and Jyoti, 1977). Interestingly, Muramoto (1981) showed that in crayfish, anal uptake of water occurs normally and is governed by a programmed motor pattern. In control animals, about 30 ^1 of water per hour are taken in anally. However, when eyestalks are removed, anal uptake of water is greatly reduced; the rate is increased again on injection of eyestalk extract. This suggests that the homeostatic mechanism normally governing uptake of water (via permeability) also regulates anal uptake. When permeability is increased, rate of anal uptake is decreased. In fact, injection of eyestalk extract into control crayfish yielded a very large increase in anal uptake of water, giving evidence for a direct action on this system unrelated to permeability of the whole animal, which might have been expected to decrease under these circumstances. In recent years, smaller crustaceans, as well as the larger decapods, have begun to be studied. In isopods, a pair of glands exists on the antennal segment, called "antennary glands." If these glands in Sphaeroma serratum are ablated by electrocautery (Charmantier and Trilles, 1977), animals exposed to dilute medium show a lower concentration of Na + and Ca ++ in hemolymph than do controls at the same salinity. They also show a greater water content than the controls. Effects on Ca ++ concentration are greater than those on Na +. An elegant study was recently carried out on larval and juvenile lobsters, Homarus americanus, by Charmantier, et al.

7 NEUROHORMONES AND OSMOREGULATION 259 (1984a, b). Stage III larvae are osmoconformers over their range of salinity, while Stage IV larvae and juveniles (Stage V) are hyperosmotic at salinities between 40% and 80% sea water. Thus the transition between Stage III and Stage IV seems to mark the beginning of osmoregulatory control. Removal of eyestalks from juveniles and Stage IVs results in a decreased osmolality and increased content of water at low salinity, similar to that seen in adult shrimps and crabs. Reimplantation of eyestalks returns the osmolality toward that of controls. Similar changes in Na + and Cl" of hemolymph are found with these treatments. However, implantation of eyestalks from Stage III larvae into destalked Stage IV larvae does not return the animals to their normal hyperionic state. In addition, implantation of Stage IV eyestalks into Stage III larvae results in high mortality and no increase in Na + concentration. Thus both the control system and the peripheral target mechanism seem to appear at this Stage Ill-Stage IV transition. Here is a system that could provide material for separation of active factors from the eyestalks of Stage III and Stage IV larvae. If the extracts are qualitatively different, a fraction present in Stage IV and not in Stage HI could be important in ionic and osmoregulatory control. Such a fraction would be very useful for further testing on in vivo or in vitro preparations, and a search for other developmental^ regulated systems might be very fruitful. NEUROENDOCRINE INTERACTIONS WITH PHYSIOLOGICAL MECHANISMS Permeability If, indeed, lipid content and composition are important in regulation of permeability, we might expect that neuroendocrine factors could affect lipid metabolism. Few data are available in crustaceans, but we know that removal of eyestalks leads to an increase in lipid synthesis in general, and that this change is not mediated by increased ecdysteroid titer. It appears instead that particular substances in the eyestalk can inhibit synthesis of lipids (O'Connor and Gilbert, 1968). There may be a parallel with the adipokinetic hormone (AKH) of locusts, which is released from the corpora cardiaca (neurohemal organs) during flight, and which causes mobilization of lipid from the insect's fat body (Orchard and Lange, 1983). The action of AKH is mediated by a cyclic AMPactivated protein kinase. AKH is very similar in structure to the crustacean red-pigment-concentrating-hormone from the eyestalk (RPCH). To my knowledge, no one has yet tested synthetic RPCH or AKH for their effects on lipid metabolism in crustacean tissues, such as midgut gland, muscle, or gill. These might be interesting experiments to carry out, particularly if we have by then the necessary data relating lipid composition to salinity of acclimation. Recent experiments by Kamemoto and Oyama (1984) bring us one step closer to the mechanism of permeability changes in the gill. Extracts of the TGM, when perfused into isolated gill, decrease influx of tritiated water, as had been seen earlier (Berlind and Kamemoto, 1977). These extracts also cause an increase in cyclic AMP (camp) levels in gill tissue, with no change in cyclic GMP. It may be that campdependent protein kinase is active in permeability changes, and further experiments with these nucleotides, both in vivo and in vitro will help to clarify the situation. In this respect, recent experiments in our laboratory indicate that injection of dibutyryl camp into intact Carcinus maenas results in a decrease in influx of tritiated water into the animal as well. We are working backwards from the important physiological effect that we first found: namely, that injection of hemolymph from a crab acclimated to 40% sea water into a crab in 100% sea water, which is then transferred to 40% sea water, results in a slower decrease in osmolality of hemolymph than in a crab that is uninjected or injected with hemolymph from an animal acclimated to 100% sea water. These results are shown in Figure 4. Thus a blood-borne factor results in either decreased permeability, or increased uptake of ions, or alterations in the cardiovascular or respiratory systems, or some combination of these changes. All have the physiological effect of reducing

8 260 LINDA H. MANTEL i-800 TOO Time (hours) 40% Injected 100% injected Unmjected "--I Fic. 4. Osmolality of hemolymph in Carcinus maenas as a function of time after transfer from 100% sw to 40% sw. Points and bars indicate mean and SEM for 5 crabs. crab not injected; crab injected with hemolymph from 100%-acclimated animal; crab injected with hemolymph from 40% acclimated animal. the rate at which osmolality of hemolymph decreases after transfer of the crab to a dilute medium. There is evidence that neuroendocrine factors may influence all of these processes, as discussed above. Active uptake Neuroendocrine extracts have been shown to increase uptake of ions into intact animals and isolated tissues. Isolated gills of Callinectes sapidus, when perfused with extracts of pericardial organ (PO), increased the rate of uptake of Na + when compared to controls. This effect was correlated with an increase in camp levels in the gill tissues as well (Kamemoto and Oyama, 1984). Thus this second messenger is implicated in the action of PO extract. When individual components of the PO were tested, dopamine and octopamine were shown to cause dramatic increases in camp, while two other components, serotonin and proctolin, a pentapeptide, did not have an effect. Perfusion of dibutyryl camp through the isolated gills also causes an increase in uptake of Na + (Kamemoto, personal communication). What is the mechanism affected by these first and second messengers? There is no definite answer as yet. However, a recent report by Savage and Robinson (1983) indicates that injection of hemolymph from a crab (C. sapidus) acclimated to dilute sea water into an animal acclimated to 100% sea water caused a rapid (within 20 min) increase in Na+K-ATPase activity in the posterior gills. We may hypothesize that the hemolymph contains a factor that acts directly on the enzyme system in the gills, perhaps by activating the enzyme molecules already present. Is there precedent for first and second messengers acting on salt transporting systems? In insects, serotonin, dopamine, and noradrenaline can stimulate fluid secretion by Malpighian tubules; and camp is thought to be the intermediary in this process. The diuretic hormone responsible for secretion in vivo has not yet been identified; it is thought to be a peptide, but active amines may also be released along with it. In addition camp concentration in Malpighian tubules increases after treatment with diuretic hormone (Nicolson and Millar, 1983; Rafaeli et al., 1984). In fishes, many hormones affect chloride secretion by Cl cells of opercular membranes. These hormones include epinephrin, somatostatin, and urotensin II, which are inhibitory; and urotensin I, glucagon, and Vasoactive Intestinal Polypeptide (VIP), which are stimulatory (Foskett et al., 1982). The stimulatory hormones also work by increasing camp levels, although the particular transport step affected is not known. Respiratory and circulatory effects Here we have even less information on relationships between neuroendocrines and osmoregulation. However, control of the circulatory and respiratory systems by the PO and its various components is becoming more clear. In Carcinus maenas, proctolin, serotonin, dopamine, and octopamine all increase ventilation rate in situ, and all except serotonin also increase activity of the isolated thoracic ganglion controlling ventilation. Sinus gland extract has no effect on ventilation (J. Wilkens, personal communication). The PO and its amines stimulate both the isolated heart and in some cases the cardiac ganglion. It is likely that control of the heart and ventilatory system is modulated in vivo by the

9 NEUROHORMONES AND OSMOREGULATION 261 same substances (McMahon and Wilkens, 1983). Further progress in this area will depend upon development of a system where osmoregulatory function can be linked directly to changes in these other processes. SUMMARY AND OUTLOOK How far, then, has this Frontier of Crustacean Endocrinology advanced in the last few years? Not very far. True, there have been some successful forays; notably into understanding of the interactions between active factors and tissues, of metabolic and enzymatic changes that occur with acclimation to various salinities, and an appreciation of the importance of respiratory and circulatory adjustments in the whole picture. We have glimmerings that bloodborne factors may be present if we find appropriate assays for them. How do we progress from here? We should take advantage of animals that change their capabilities for osmoregulation at different stages of development, such as the larvae of Homarus. There must be others not yet discovered. We should test some active neuroendocrine fractions or hemolymph from osmoregulators on osmoconformers, to see if we can get changes in function of tissues or in responses of the intact animals. We should look more closely at the relationships between lipids and transport-related enzymes. We should find some crustaceans in which we can truly measure blood flow over the gills, to see whether this is affected by change in the external medium or the application of active factors. Finally, we should talk and listen more attentively to the fish and insect people, and try some of their active factors on our animals; keeping in mind, however, the caveat of Greenberg and Price, (1983) "analgous physiological roles in different classes and phyla are rarely carried out by homologous peptides." All of these efforts should help to advance the frontier apace. ACKNOWLEDGMENTS Research in my laboratory is supported by the PSC/BHE Faculty Research Award Program of the City University of New York, and by the Department of Environmental Protection of the State of New Jersey. I appreciate the support of the Biology Department of City College and the Department of Invertebrates of the American Museum of Natural History for technical, library, and word-processing facilities. Finally, I thank my former and present students, Angela Cristini, Joseph Olson, Jeff Landesman, Ed Flynn, and Michael Sommer, for their contributions to this effort. REFERENCES Barra, J-A., A. Pequeux, and W. Humbert A morphological study on gills of a crab acclimated to fresh water. Tissue and Cell 15: Berlind, A. and F. I. Kamemoto Rapid water permeability changes in eyestalkless euryhaline crabs and in isolated perfused gills. Comp. Biochem. Physiol. 58A: Bliss, D. E Transition from water to land in decapod crustaceans. Amer. Zool. 8: Cantelmo, A. C Water permeability of isolated tissues from three species of decapod crustaceans with respect to osmotic conditions and effects of neuroendocrine factors. Ph.D. Diss., City University of New York, New York. Cantelmo, A. C Water permeability of isolated tissues from Decapod crustaceans. 1. Effect of osmotic conditions. Comp. Biochem. Physiol. 58A: Chapelle, S., R. Meister, G. Brichon, and G. Zwingelstein Influence of temperature on the phospholipid metabolism of various tissues from the crab Carcinus maenas. Comp. Biochem. Physiol. 58B: Chapelle, S., G. Dandrifosse, and G. Zwingelstein Metabolism of phospholipids of anterior or posterior gills of the crab Eriocheir sinensis M. Edw. during the adaptation of this animal to media of different salinities. Int. J. Biochem. 7: Charmantier, G. and J-P. Trilles Influence des glandes antennaires sur la regulation ionique, la teneur en eau et eventuellement la mue de Sphaeroma serratum (Crustacea, Isopoda, Flabellifera). Gen. Comp. Endocrinol. 31: Charmantier, G., M. Charmantier-Daures, and D. E. Aiken. 1984a. Neuroendocrine control of hydromineral regulation in the American lobster Homarus americanus H. Milne Edwards 1837 (Crustacea, Decapoda). 1. Juveniles. Gen. Comp. Endocrinol. 54:8-19. Charmantier, G., M. Charmantier-Daures, and D. E. Aiken Neuroendocrine control of hydromineral regulation in the American lobster, Homarus americanus H. Milne Edwards 1837 (Crustacea, Decapoda). 2. Larval and postlarval stages. Gen. Comp. Endocrinol. 54: Cooke, I. M. and R. E. Sullivan Hormones and neurosecretion. In H. Atwood and D. Sandeman (eds.), The biology of Crustacea, Vol. 3, pp Academic Press, New York. Copeland, D. E. and A. T. Fitzjarrell The salt

10 262 LINDA H. MANTEL absorbing cells in the gills of the blue crab (Callinectes saptdus Rathbun) with notes on modified mitochondria. Z. Zellforsch. 92:1-22. Davis, C. W Neuroendocrine control of sodium balance in the fiddler crab Uca pugilator. Ph.D. Diss., University of North Carolina, Chapel Hill, North Carolina. DePew, E. F. and D. W. Towle Bicarbonatestimulated ATPase in plasma membrane fractions of fiddler crab (Uca minax) gill. Mar. Biol. Lett. 1: De Leersnyder, M Le milieu interieur d'eriocheir sinensis Milne-Edwards et ses variations. II Etude experimentale. Cah. de Biol. Marine 8: Foskett, J. K., G. M. Hubbard, T. E. Machen, and H. A.Bern Effects of epinephrin, glucagon, and vasoactive intestinal peptide on chloride secretion by teleost opercular membrane. J. Comp. Physiol. 146: Greenberg, M.J.andD. A. Price Invertebrate neuropeptides: Native and naturalized. Ann. Rev. Physiol. 45: Hannan.J. and D. Evans Water permeability in some euryhaline decapods and Limulus polyphemus. Comp. Biochem. Physiol. 44A: Heit, M. and M. Fingerman The role of an eyestalk hormone in the sodium concentration of the blood of the fiddler crab, Uca pugilator. Comp. Biochem. Physiol. 50A: Henry, R. P. and J. W. Cameron The role of carbonic anhydrase in respiration, ion regulation, and acid-base balance in the aquatic crab Callinectes sapidus and the terrestrial crab Gecarcinus lateralis. J. Exp. Biol. 103: Holliday, C. W Aspects of antennal gland function in the crab, Cancer magister (Dana). Ph.D. Diss., University of Oregon, Eugene, Oregon. Hume, R. I. and A. Berlind Heart and scaphognathite rate changes in a euryhaline crab, Carcinus maenas, exposed to dilute environmental medium. Biol. Bull. (Woods Hole, Mass.) 150: Kamemoto, F. I Neuroendocrinology of osmoregulation in decapod Crustacea. Amer. Zool. 16: Kamemoto, F. I. and S. N. Oyama Neuroendocrine influence on effector tissues of hydromineral balance in crustaceans. In B. Lofts (ed.), Ninth International Symposium on Comparative Endocrinology proceedings. Hong Kong University Press. Kamemoto, F. LandR.E.Tullis Hydromineral regulation in decapod Crustacea. Gen. Comp. Endocrinol. 3: Mantel, L. H., D. E. Bliss, S. W. Sheehan, and E. A. Martinez Physiology of hemolymph, gut fluid, and hepatopancreas of the land crab Gecarcinus lateralis (Freminville) in various neuroendocrine states. Comp. Biochem. Physiol. 51 A: Mantel, L. H. and L. L. Farmer Osmotic and ionic regulation. In L. H. Mantel (ed.), The biology of Crustacea, Vol. 5, pp Academic Press, New York. McMahon, B. R. and J. L. Wilkens Ventilation, perfusion, and oxygen uptake. In L. H. Mantel (ed.), The biology of Crustacea, Vol. 5, pp Academic Press, New York. Morris, R. J., A. P. M. Lockwood, and M. E. Dawson An effect of acclimation salinity on the fatty acid composition of the gill phospholipids and water flux of the amphipod crustacean Gammarusduebeni. Comp. Biochem. Physiol. 72A: Muramoto, A Effects of eyestalk extracts and ecdysterone on water intake through the anus of the crayfish. Comp. Biochem. Physiol. 69A: Nagabhushanam, R. and M. Jyoti Hormonal control of osmoregulation in the fresh water prawn Caridina weberi. J. Anim. Morph. Physiol. 24: Nicolson, S. W. and R. P. Millar Effects of biogenic amines and hormones on butterfly Malpighian tubules: Dopamine stimulates fluid secretion. J. Ins. Physiol. 29: Norfolk, J. R. W Internal volume and pressure regulation in Carcinus maenas. J. Exp. Biol. 74: O'Connor, J. D. and L. I. Gilbert Aspects of lipid metabolism in crustaceans. Amer. Zool. 8: Orchard, I. and A. B. Lange The hormonal control of haemolymph lipid during flight in Locusta migratoria. J. Ins. Physiol. 29: Rafaeli, A., M. Pines, P. Stern, and S. W. Applebaum Locust diuretic hormone-stimulated synthesis and excretion of cyclic AMP: A novel Malpighian tubule bioassay. Gen. Comp. Endocrinol. 54: Savage, J. P. and G. D. Robinson Inducement of increased gill Na + K-ATPase activity by a hemolymph factor in hyperregulating Callinectes sapidus. Comp. Biochem. Physiol. 75A: Smith, R. I Osmotic regulation and adaptive reduction of water-permeability in a brackishwater crab, Rhtthropanopeus harrisii (Brachyura, Xanthidae). Biol. Bull. (Woods Hole, Mass.) 133: Smith, R. I The apparent water-permeability of Carcinus maenas (Crustacea, Brachyura, Portunidae) as a function of salinity. Biol. Bull. (Woods Hole, Mass.) 139: Thuet, P Etude des flux de diffusion de I'eau en fonction de la concentration du milieu exterieur chez l'isopode Sphaeroma serratum (Fabricius). Arch. Int. Physiol. Biochim. 86: Towle, D. W. 1984a. Membrane-bound ATPases in arthropod ion-transporting tissues. Amer. Zool. 24: Towle, D.W Regulatory functions of Na+K- ATPase in marine and estuarine animals. In A. Pequex, R. Grilles,and L. Bolis(eds.), Osmoregulation in estuarine and marine animals, pp Springer-Verlag, Berlin. Towle, D. V\'., W. T. Kays, and M. Cioffi

11 NEUROHORMONES AND OSMOREGULATION 263 Localization of Na+K-ATPase in basolateral Whitney, J. O The effect of external salinity membranes of crab gill ion-transporting cells. upon lipid synthesis in the blue crab Callinectes Amer. Zool. 23:953. sapidus Rathbun and the spider crab Libinia emar- Tullis, R. and F. I. Kamemoto Separation and ginata Leach. Comp. Biochem. Physiol. 49A:433- biological effects of CNS factors affecting water 440. balance in the decapod crustacean Thalamita crenata. Gen. Comp. Endocrinol. 23:19-28.

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