Osmolality and electrolyte concentration of hemolymph and the problem of ion and volume regulation of cells in higher insects

• 1.1. The study was carried out on 22 species of insects from 5 orders. The osmolality of their hemolymph varied from 319 to 421 mOsm/kg H₂O, concentration of Na⁺ 4.6 to 118 mM/l, K⁺ 6.3 to 73mM/l, Ca²⁺ 3.6 to 12.9 mM/l, Mg²⁺ 2.3 to 76 mM/l. The most abundant cation in the hemolymph of insects from higher orders is either K⁺ or Mg²⁺.
• 2.2. In the muscles of lower and higher insects K⁺ is usually within 80–120 mM/kg wet wt.
• 3.3. Most Ca²⁺ and Mg²⁺ in hemolymph is bound with protein and low molecular anions, concentration of free Ca²⁺ is 0.9-2.1mM/l Mg²⁺ 3.7–8.0 mM/l.
• 4.4. It is concluded that, in insects, potassium hemolymph, cell volume regulation and accumulation of ions in the cell, are ensured by an increased osmolality of hemolymph due to a high percentage contribution of low molecular organic substances which are retained in the hemolymph due to the absence of filtration apparatus in the Malpighian tubules.

     

Salinity-dependence of the properties of gill (Na++K+-ATPase in rainbow trout Oncorhynchus mykiss

• 1.1. The expected higher gill (Na⁺+K⁺)-ATPase activity in rainbow trout adapted to brackish water (BW) with respect to fresh water (FW) is accompanied by some changes in the enzyme kinetics while the enzyme sensitivity to ouabain is unaffected
• 2.2. Maximal activation is attained under the optimal conditions of 4 mM ATP, 7.5 mM Mg²⁺, 50 mM Na⁺, 2.5 mM K⁺, pH 7.0 in FW, and 3 mM ATP, 10 mM Mg²⁺, 100 mM Na⁺, 10 mM K⁺, pH 7.5 in BW.
• 3.3. The change of the enzyme activation kinetics by Mg²⁺, ATP, Na⁺ and K⁺ from simple saturation in FW to cooperativity in BW and other habitat-dependent variations including the pH alkaline shift in BW are hypothetically related to an adaptive significance to the different environmental salinity.
• 4.4. Gill total lipids and phospholipids are 30% lower in BW than in FW while their ratio is constant; some differences in gill total lipid fatty acid composition between FW and BW do not significantly affect the unsaturation parameters.

     

Effect of warm acclimation on the cationic concentrations in the extracellular and intracellular body fluid of hibernating Rhagium inquisitor beetles

• 1.1. The effect of warm acclimation on the cationic concentrations of hibernating Rhagium inquisitor beetles was studied.
• 2.2. Following warm acclimation, the extracellular concentration of Mg²⁺ dropped from about 80 to about 50 mM. For Na⁺ and K⁺ the extracellular concentration remained constant at about 40 mM. The estimated intracellular concentration of Mg²⁺ was not affected by the warm acclimation, being about 80 mM in both groups of beetles. The corresponding concentration of Na⁺ increased from about 20 to about 30 mM, whereas for K⁺ there was no change, the concentration being about 140mM in both groups of beetles.
• 3.3. The marked drop in the extracellular concentration of Mg²⁺ might indicate that Mg²⁺ is involved in the regulation of the concentration of glycerol, which was reduced to zero during the warm acclimation.
• 4.4. The estimated equilibrium potentials of the respective ions might indicate that K⁺ is in electrochemical equilibrium across the cell membranes, whereas Na⁺ and to a lesser extent Mg²⁺ are actively transported out of the cells.
• 5.5. For Na⁺ there was a high positive equilibrium potential even in the cold acclimated beetles, indicating that Na⁺ has a high electrochemical potential difference across the cell membranes even at low temperatures. This is in agreement with the observation that hibernating insects are able to perform coorclinated walking immediately after heating to temperatures near zero.

     

Mg2+-dependent (Na+ + K+)- and Na+-ATPases in the kidneys of the gilthead bream (Sparus auratus L.)

• 1.1. The (Na⁺ + K⁺)- and Na⁺-ATPases, both present in kidney microsomes of Sparus auratus L., have different activities and optimal assay conditions as, in the first of the two stocks of fish used (A), the spec. act. of the former is 51.7 μmol P_i mg prot⁻¹ hr⁻¹ at pH 7.5, 100 mM Na⁺, 10 mM K⁺, 17.5 mM Mg²⁺, 7.5 mM ATP and that of the latter is 6.5 μmol P_i mg prot⁻¹ hr⁻¹ at pH 6.5, 40 mM Na⁺, 4.0 mM Mg²⁺, 2.5 mM ATP.
• 2.2. Ouabain and vanadate specifically inhibit the (Na⁺ + K⁺)-ATPase but not the Na⁺-ATPase that is preferentially inhibited by ethacrynic acid.
• 3.3. While the (Na⁺ + K⁺)-ATPase is strictly specific for ATP and Na⁺, Na⁺-ATPase can be activated by various monovalent cations and, apart from ATP, hydrolyses CTP, though less efficiently.
• 4.4. The second stock B, subjected to higher salinity than A, shows an acidic shifted Na⁺-ATPase optimal pH, opposed to the stability of that of the (Na⁺ + K⁺)-ATPase, a decreased (Na⁺ + K⁺)-ATPase and a strikingly depressed Na⁺-ATPase.
• 5.5. The results are compared with literature data and discussed on the basis of the presumptive different roles as well as functional prevalence in various salinities of the two ATPases.

     

Effects of Na+ and/or K+ on the Mg2+-dependent ATPase activities in shrimp (Macrobrachium amazonicum) gill homogenates

• 1.1. Homogenates of gills from the freshwater shrimp M. amazonicum exhibit the following ATPase activities: (i) a basal, Mg²⁺-dependent ATPase; (ii) an ouabain-sensitive, Na⁺ + K⁺-stimulated ATPase; (iii) an ouabain-insensitive, Na⁺-stimulated ATPase; and (iv) an ouabain-insensitive, K⁺-stimulated ATPase.
• 2.2. K⁺ suppresses the Na⁺-stimulated ATPase activity in a mixed-type kind of inhibition, whereas Na⁺ does not exert any noticeable effect on the K⁺-stimulated ATPase activity.
• 3.3. The Na⁺- and the K⁺-stimulated ATPase activities are totally inhibited by 5 mM ethacrynic acid in the incubation medium.
• 4.4. The Na⁺- and the K⁺-stimulated ATPase activities are not expressions of the activation of a Ca-ATPase.
• 5.5. The possible localization and roles of the described ATPases within the gill epithelium are briefly discussed and evaluated.

     

The possibility that Ca2+-ATPase from the plasma membrane-rich fraction of bovine parotid gland is ecto-Ca2+-dependent nucleoside triphosphatase

• 1.1. Parotid plasma membrane nonpump low-affinity Ca²⁺-ATPase, which possesses high-affinity (Ca²⁺ + Mg²⁺ )-ATPase activity, was characterized.
• 2.2. Purified Ca²⁺-ATPase hydrolyzed the nucleoside triphosphates, GTP, ITP, CTP, UTP, TTP (67–93% of ATP) and nucleoside diphosphates, ADP. GDP, IDP, CDP, TDP (12–40% of ATP) but not AMP and p-NPP.
• 3.3. The maximum activities of Ca²⁺- and (Ca²⁺ +Mg²⁺ )-ATPases were obtained in the presence of 1 mM and 0.13 μ M Ca²⁺, respectively.
• 4.4. The K_m values for Ca²⁺ in Ca²⁺- and (Ca²⁺+ Mg²⁺ )-ATPases were 0.2 mM and 22 nM. respectively.
• 5.5. The activities of both Ca²⁺- and (Ca²⁺ + Mg²⁺ )-ATPases were found in the right-side-out-vesicles obtained from the plasma membrane-rich fraction.
• 6.6. These features suggest that Ca²⁺-ATPase is an ecto-Ca²⁺-dependent nucleoside triphosphatase.

     

Properties and distribution of Mg2+-HCO−3-ATPase in brush border membranes isolated from rat small intestine

• 1.1. The small intestine was cut into seven segments and properties and distribution of brush border Mg²⁺-HCO⁻₃-ATPase activity in each segment were examined.
• 2.2. The optimal Mg²⁺ concentration was 1.0 mM.
• 3.3. The optimal HCO⁻₃ concentration was 100 mM in the first (duodenal), 50 mM in the 3rd and 40 mM in the 5th segment, respectively.
• 4.4. The optimal pH value was about 9.0.
• 5.5. l-phenylalanine (above 1 mM) and SCN⁻ (above 50 mM) significantly inhibited both Mg²⁺- and Mg²⁺-HCO⁻₃-ATPase activity.
• 6.6. The enzyme activity was found to be highest in the duodenal segment and then gradually decreased in consecutive segments as well as β-glycerophosphatase, Na⁺-K⁺-ATPase and supernatant carbonic anhydrase.
• 7.7. The functional significance of this ATPase and the relationship with carbonic anhydrase was discussed.

     

Erythrocyte membrane anion-sensitive Mg2+-ATPase—Identity with monovalent cation sensitive Ca2+-Mg2+-ATPase

• 1.1. Activation of Mg²⁺-ATPase of rabbit and guinea-pig erythrocyte membrane by bicarbonate or chloride could be completely abolished by ethylene-glycol-bis-(β-aminoethylether)-N,N'-tetraacetic acid. The anion stimulation was actually an activation of contaminating Ca²⁺ -stimulated Mg²⁺-ATPase by monovalent cations associated with the anions.
• 2.2. Guinea-pig red cell Ca²⁺-Mg²⁺-ATPase could be activated by both sodium and potassium while the rabbit enzyme was sensitive only to sodium. The concentrations of monovalent cations for half-maximal stimulation of Ca²⁺-Mg²⁺-ATPase are: k_na+ = 40.8 mM, k_k+ = 12.2 mM (guinea-pig); K_Na+ = 13.3mM (rabbit).
• 3.3. Potassium enhanced activation of rabbit erythrocyte membrane Ca²⁺-Mg²⁺-ATPase by red cell Ca²⁺-Mg²⁺-ATPase activator protein. With the guinea pig enzyme, neither sodium nor potassium enhanced activator stimulation of Ca²⁺-Mg²⁺-ATPase.
• 4.4. Ca²⁺-Mg²⁺-ATPase of aged rabbit erythrocyte membrane responded to sodium but not to activator protein.
• 5.5. Triton X-100 solubilized rabbit erythrocyte membrane Ca²⁺-Mg²⁺-ATPase has an apparent molecular weight of 371,000. It did not respond to the activator.
• 6.6. One major and three minor proteins, visualized by SDS-polyacrylamide gel electrophoresis, were extracted from rabbit erythrocyte membrane by 50 μM chlorpromazine.

     

Ionic dependence and vanadate sensitivity of (Na+, K+)-ATPase isolated from branchial sac of ascidians

• 1.1. Ion dependence and vanadium-induced inhibition on branchial sac ATPase in five species of ascidian Phlebobranchiata (vanadium-accumulating) and Stolidobranchiata (iron-accumulating) were studied.
• 2.2. The ATPase was obtained from the microsomal fraction, which was prepared from each ascidian branchial sac.
• 3.3. The ATPase was dependent on Mg²⁺ and activated by exogenous Na⁺ + K⁺.
• 4.4. Ouabain inhibited the ATPase activity in vitro, 10 μM to 100 μM vanadate, in vitro, suppressed the (Na⁺, K⁺)-ATPase.

     

The exchange of radioactive cations by somatic and cardiac muscles of the crayfish

• 1.1. Intracellular concentrations of Na⁺, K⁺, Ca²⁺ and Mg²⁺ were measured in a somatic muscle and in the heart of the crayfish. The uptake and the efflux of Na²⁴, K⁴², Ca⁴⁵ and of Sr⁸⁹ were also measured.
• 2.2. The initial influx rates of the ions from van Harreveld's solution into resting somatic muscle (in μEq/g cell water/hr) are: K⁺ = 25; Na⁺ = 56; Ca²⁺ = 38. Similar figures were obtained for the heart muscle.
• 3.3. The calculated permeability constants (× 10⁸ cm/sec) are: P_K = 64; P_Na = 30 P_Ca = 10; P_Sr = 1·5.
• 4.4. The stimulation of the muscle fiber leads to an additional Ca²⁺ influx of about 2·8 pEq/cm² fiber surface. The additional Ca²⁺ uptake is sufficient to account for the change in potential on the membrane.
• 5.5. When muscles were immersed in Sr²⁺ solutions, no additional Sr⁸⁹ uptake was found with stimulation. However, there is a high resting Sr⁸⁹ uptake and the muscle in Sr²⁺ has a long refractory period, so a reasonable increase in Sr⁸⁹ uptake would not be detectable.
• 6.6. The results are discussed in relation to the divalent cation mechanism for generating action potentials and to the part played by Ca²⁺ in triggering contraction.

     

Ca2+ - and Mg2+-dependent ATPase activities in the deoxycholate-treated rat heart sarcolemma

• 1.1. Isolated rat heart sarcolemma was treated with different concentrations of an ionic detergent, deoxycholate (DOC) and ATP hydrolysis in the presence of Ca²⁺ or Mg²⁺ was determined.
• 2.2. Both Ca²⁺-dependent ATPase and Mg²⁺-dependent ATPase activities were decreased in the DOC-treated membranes; however, the depression of Mg²⁺-dependent ATPase activity was greater than that of Ca²⁺-dependent ATPase.
• 3.3. The differential changes in Ca²⁺-dependent ATPase and Mg²⁺-dependent ATPase activities were apparent when incubations with DOC were carried out for different time intervals and at different temperatures.
• 4.4. In DOC-treated preparations, the K_m value for Ca²⁺-dependent ATPase was decreased whereas that for Mg²⁺-dependent ATPase was increased. The half maximal velocities of the Ca²⁺-dependent ATPase and Mg²⁺-dependent ATPase enzyme reactions in the treated preparations were obtained at a DOC: membrane protein ratio of 3.0 and 0.6, respectively.
• 5.5. In the DOC-treated membranes exhibiting the half maximal velocities of enzyme reactions, the K_i value for Ca²⁺-dependent ATPase was drastically reduced but remained unchanged for Mg²⁺-dependent ATPase.
• 6.6. The DOC treatment was associated with a loss of protein as well as phospholipids and resulted in changes in the ultrastructural integrity of the membrane.
• 7.7. Varying degrees of decreases in the activities of sarcolemmal adenylate cyclase. (Na⁻-K⁺)-ATPase. 5'-nucleotidase and calcium binding were seen upon DOC treatment.
• 8.8. The extent of reduction in Ca²⁺-dependent ATPase and Mg²⁺-dependent ATPase activities were also different when the membrane was treated with a non-ionic detergent, Lubrol PX.
• 9.9. These data suggest that Ca²⁺-dependent ATPase in heart sarcolemma is more resistant than Mg²⁺-dependent ATPase to detergent treatments and further indicate some differences in the properties of these enzymes.

     

The sea urchin extraembryonic hyaline layer: Ionic parameters controlling the hyalin gelation reaction

• 1.1. As reported previously (Robinson, 1988) the Ca²⁺-induced self-association reaction of the protein hyalin, purified from the sea urchin extraembryonic hyaline layer, was modulated by both Mg²⁺ and NaCl.
• 2.2. In the presence of 400 mM NaCl the apparent dissociation constant (Ca²⁺) decreased five-fold from 4.8 ± 1.1 mM in the absence to 0.9 ± 0.5 mM in the presence of 20 mM Mg²⁺.
• 3.3. The potentiating effect of Mg²⁺ occurred with an apparent dissociation constant (Mg²⁺) of 4.6 ± 0.5mM.
• 4.4. In the absence of Ca²⁺ or NaCl hyalin dissociated from isolated hyaline layers indicating that the behavior of hyalin within the layer is predictable from results obtained with the purified protein.

     

The effect of salinity on coelomic fluid osmolyte concentration and intracellular water content in Luidia clathrata (Say) (Echinodermata: Asteroidea)

• 1.1. The concentrations (mM) of osmolytes in the coelomic fluid of Luidia clathrata kept at 25‰S seawater (control individuals) were: 345, Na⁺; 10, K⁺; 10, Ca²⁺; 44, Mg²⁺; 387, Cl⁻; 0.67, amino acids; 0.09, NH₄⁺.
• 2.2. When individuals were transferred from 25‰S to 15‰S or 35‰S, the concentrations of inorganic ions in the coelomic fluid usually equilibrated within 24hr and became the same as those in the medium.
• 3.3. The intracellular water content (g intracellular H₂O/g solute-free dry tissue) of the pyloric caeca and tube feet of control individuals throughout the experiment was 2.13 and 5.40, respectively.
• 4.4. In tissues of individuals transferred to 15‰S, the intracellular water content increased by an average 50% in 12 hr but returned to 19% above control levels during 1 week.
• 5.5. In tissues of individuals transferred to 35‰S, the intracellular water content decreased by an average 17% in 12 hr and did not change during 1 week.
• 6.6. Luidia clathrata is an osmoconformer and partial cell volume regulator within the seasonal salinity range it encounters.

     

High-affinity Ca2+-Mg2+-ATPase in kidney of euryhaline Gillichthys mirabilis: kinetics,subcellular distribution and effects of salinity

• 1.1. Two components of Ca²⁺-Mg²⁺-ATPase are observed in kidneys of G. mirabilis. The high-affinity component has a K_0.5Ca of 0.23μM; the low-affinity activity K_0.5Ca is 90–110μM. The high-affinity activity requires Mg²⁺, displays Michaelis-Menten kinetics, has peak activity at 1.2 μM Ca²⁺, and is insensitive to ouabain and Na⁺ azide.
• 2.2. In subcellular fractions, the high-affinity component segregates with Na⁺-K⁺-ATPase and is localized predominantly in BLM. The low-affinity component is broadly distributed among membranous organelles, including brush border, and may be equivalent to alkaline phosphatase.
• 3.3. Specific activity of the high-affinity Ca²⁺-Mg²⁺-ATPase is modestly increased following adaptation of fish to FW, but total renal high-affinity activity is greatest in the hypertrophied kidneys of FW-adapted fish and is least in kidneys of fish adapted to 200% SW.
• 4.4. High-affinity Ca²⁺-Mg²⁺-ATPase may be associated with active Ca²⁺ transport or with regulation of intracellular Ca²⁺ concentration of tubular cells.

     

Calcium-dependent potassium conductance in the photoresponse of a nudibranch mollusk

• 1.1. The response to light of Hermissenda photoreceptors when recorded intracellularly without interference from synaptic and action potentials consisted of three phases: an early depolarization (ED) followed by hyperpolarization (dip) and subsequent depolarization (tail).
• 2.2. The ED and the dip were associated with increased membrane conductance while decreased membrane conductance was involved with the tail.
• 3.3. The dip reversal potential was − 82.1 ± 5.3 mV and its amplitude varied inversely with the log of [K⁺].
• 4.4. Perfusing with agents which block K⁺ current like 4AP, Quinine, Quinidine or injection of TEA eliminated the dip and its associated increased membrane conductance, thus further supporting the role of K⁺ conductance in producing the dip.
• 5.5. The dip was enhanced by increased [Ca²⁺]_o, reduced by decreased [Ca²⁺]_o and abolished together with its associated increased membrane conductance when perfused with either D600, Cd²⁺, Mg²⁺, Mn²⁺, or Co²⁺, which block transmembrane Ca²⁺ current.
• 6.6. The dip and its associated increased membrane conductance were abolished by intracellular injection of EGTA and enhanced by perfusion with Ruthenium red.
• 7.7. Intracellular injection of Ca²⁺ mimicked the dip: membrane conductance was increased and the cell hyperpolarized.
• 8.8. These results indicate that the increase in intracellular [Ca²⁺] is primarily responsible for the light-induced increase of K⁺ conductance during the dip. The possible source of the Ca²⁺ is, at least in part, extracellular due to activation of an inward Ca²⁺ current.

     

Ca2+-binding and protein-protein interaction domains of the sea urchin extraembryonic coat protein hyalin

• 1.1. As reported previously (Hopper and Robinson, 1990; Int. J. Biochem. 22, 1165–1170) the sea urchin extraembryonic coat protein hyalin undergoes a Ca²⁺-induced self-association into an insoluble gel (gelation) in the presence of Mg²⁺ and/or NaCl.
• 2.2. A 275 kDa peptide fragment, generated by limited tryptic digestion of hyalin, binds Ca²⁺+ but does not undergo gelation in the presence of Ca²⁺, Mg²⁺ and NaCl.
• 3.3. Comparisons between the capacities of hyalin and the 275 kDa peptide fragment to bind Ca²⁺ indicate that the latter binds 88% less Ca²⁺ than hyalin.
• 4.4. However, the presence of Ca²⁺ alone, at a concentration of 5 mM, protects the 275 kDa peptide fragment from further digestion by trypsin mimicking the effect of this cation in protecting hyalin.
• 5.5. Gel exclusion Chromatographie analyses of the 275 kDa peptide fragment, both in the presence and absence of 5 mM Ca²⁺, indicate that this cation does induce self-association of the fragment.
• 6.6. These results provide information on the organization of the functional domains on hyalin which are required for gel formation.

     

Behaviour and haemolymphatic ionic composition of the intertidal crab Chasmagnathus granulata dana, 1851 (Crustacea: Decapoda) during emersion

• 1.1. Behavioural observations and haemolymphatic measurements of Na⁺ K⁺ and Ca⁺ were performed in Chasmagnalhus granulata during emersion.
• 2.2. Activity levels were found to be higher during voluntary emersion periods than when the animals were submerged. A lt₅₀ of 39.45 hr was observed when no access to water was allowed.
• 3.3. The Na⁺ and K⁺ and Ca⁺ levels increased during aerial exposure. The Na⁺ and K⁺ levels were restored prior the end of the experimental period. Mechanisms for such regulation are therefore discussed. The Ca²⁺ levels, remaining high during emersion, are probably a result of acid-base balance adjustments.

     

Protein digestion and ion concentrations in rainbow trout (Salmo gairdnerii Rich.) digestive tract in sea- and fresh water

• 1.1. Rainbow trout maintained in fresh water or Actapted to sea-water for 24 hr were fed casein-based dry diet. After feeding, fish were kept in fresh water (FW) or transferred to artificial sea-water (SW) and sacrificed after 10 or 20 hr.
• 2.2. The digestive tract was separated into five parts: stomach, pyloric caeca region, middle intestine and two equal lengths of rectum.
• 3.3. The content of these parts was analysed for ions Na⁺, K⁺, Cl⁻, Mg²⁺ and for free, peptide and total amino acids.
• 4.4. In the fish stomach all ions, with the exception of Ca²⁺, indicate drinking of sea-water. In the pyloric caeca region Na⁺ appears to be efficiently absorbed in SW fish but influxed in FW fish. In the rectum of SW fish K⁺ appears to be reabsorbed but Na⁺ concentrated in faeces.
• 5.5. Free amino acid concentrations were always higher in gut lumen of SW than in FW fish in respect to time after feeding and portion of intestinal content. Free amino acids constitute at most 7.4–8.7% of total amino acids in the content of pyloric caeca region.
• 6.6. Peptide amino acids, being mostly di-, tri- and tetra-peptides, increased in stomach content from 14.7 to 28.4% of the total, from 6 to 10 hr after a meal in SW fish. Peptide amino acids constituted 80.3–89.0% of total amino acids in intestinal content of the pyloric caeca region. These peptide portions decreased in the mid-intestine (47.5–52.5%) and increased again in the rectum (73.6–76.0%).
• 7.7. It was concluded that in rainbow trout fed in both sea- or fresh water, ion concentrations do not seem to interfere with protein digestion and nutrient absorption in alimentary tract.

     

Crayfish retinular cells: Influence of extracellular sodium and calcium upon receptor potential

• 1.1. In crayfish, light stimulation of the retinular cells induces a depolarizing receptor potential.
• 2.2. Experiments were designed to determine the role of Na⁺ and Ca²⁺ on receptor potential during dark And light states.
• 3.3. Depolarization depends on Na⁺ and Ca²⁺ availability to the retinular cell.
• 4.4. Repolarization velocity and response duration depend on extracellular Ca²⁺ availability.
• 5.5. Light adaptation increases receptor potential dependence on calcium and sodium ions.
• 6.6. We analyse these results with respect to other invertebrate photoreceptors.

     

Hemolymph osmo-ionic concentrations in terrestrial crabs following desiccation

• 1.1. The hemolymph osmotic, Na⁺ K⁺, Ca⁺⁺ and Mg⁺⁺ concentrations were determined for both sexes in crabs from mangrove Ucides cordatus and Goniopsis cruentata and supralittoral Ocypode quadrala after aerial desiccation, for 10 hr.
• 2.2. There was no difference between sexes in the two mangrove crabs, but in O. quadrata the females were the most significantly affected (P < 0.01).
• 3.3. Hemolymph osmotic Na⁺, Ca⁺⁺ and Mg⁺⁺ concentrations increased significantly in desiccated ghost crabs, while K ⁺ concentration was not significantly changed. In the two mangrove crabs, only hemolymph Ca⁺⁺ concentration increased significantly, after desiccation.
• 4.4. The short time desiccation is suggested to be a device to study the steps of osmo-ionic regulation in terrestrial crabs.