Perireceptor mechanisms sustaining olfaction at low salinities: insight from the euryhaline blue crab Callinectes sapidus

1997 ◽  
Vol 200 (3) ◽  
pp. 445-456 ◽  
Author(s):  
R Gleeson ◽  
M Wheatly ◽  
C Reiber
Keyword(s):  
Blue Crab ◽  
Time Course ◽  
Structural Integrity ◽  
Sea Water ◽  
Callinectes Sapidus ◽  
Electrical Potential ◽  
Olfactory Response ◽  
Olfactory Sensilla ◽  
Low Salinity ◽  
Fluid Compartments

As the blue crab Callinectes sapidus moves from sea water to fresh water, the 'exposed' chemosensory dendrites in the olfactory sensilla (aesthetascs) undergo changes in length that are positively correlated with environmental salinity. In this study, we demonstrate the following. (1) The responses of the olfactory receptor cells of freshwater-acclimated crabs are reduced relative to those of seawater-acclimated animals, but increase with a time course comparable to the increase in dendrite length when these crabs are transferred to sea water. (2) The olfactory response of seawater-acclimated crabs is lost and the chemosensory dendrites osmotically ablated if the aesthetascs are acutely exposed to low salinity. However, maintaining iso-osmotic conditions with mannitol preserves both the physiological response and the structural integrity of the dendrites. (3) The flux of [14C]thiocyanate and 22Na between the hemolymph and sensillar lymph of the aesthetascs indicates continuity between these fluid compartments. (4) There is a net efflux of Na+ from the hemolymph through the aesthetascs in freshwater-acclimated crabs, and measurements of electrical potential across the antennules suggest that this efflux largely derives from passive diffusion. (5) Dendrites in the aesthetascs of crabs acclimated to brackish water are intermediate in length between those of freshwater- and seawater-acclimated animals. Together, our findings suggest that, at low salinities, the efflux of Na+ (and probably other ions) from the hemolymph generates an ionic/osmotic microenvironment within the aesthetascs that sustains the structural and functional integrity of the olfactory dendrites. We propose that the length of these dendrites, and consequently the olfactory response, is constrained by the distance over which this microenvironment can be effectively maintained.

Sustaining olfaction at low salinities: mapping ion flux associated with the olfactory sensilla of the blue crab Callinectes sapidus

2000 ◽  
Vol 203 (20) ◽  
pp. 3145-3152 ◽  
Author(s):  
R.A. Gleeson ◽  
K. Hammar ◽  
P.J. Smith
Keyword(s):  
Fresh Water ◽  
Sea Water ◽  
Callinectes Sapidus ◽  
External Environment ◽  
Structural Data ◽  
Olfactory Sensilla ◽  
Low Salinity ◽  
Ion Movement ◽  
Ion Efflux ◽  
Net Flux

To test the hypothesis of a diffusion-generated, ionic/osmotic microenvironment within the olfactory sensilla (aesthetascs), flux gradients of Ca(2+) and K(+) associated with the external surfaces of these sensilla were spatially mapped using self-referencing, ion-selective microelectrodes. Blue crabs (Callinectes sapidus) acclimated to low-salinity conditions (15% sea water and fresh water) showed a net efflux of ions from the aesthetascs. The region of maximum flux associated with each aesthetasc conformed to that predicted from structural data and corresponded to the permeable region of the cuticle separating the olfactory dendrites from the external environment. Estimates of net flux from the entire tuft of aesthetascs for both Ca(2+) and K(+) fell within the predicted range on the basis of comparisons with (22)Na(+) flux measured previously and assuming a passive diffusion model of ion movement from the hemolymph to the sensillar lymph and, ultimately, to the external environment. The maximum concentrations of these ions measured deep within the tuft are discussed in the light of a potential across the aesthetascs that may limit ion efflux at low salinities.

Post-Moult Calcification in the Blue Crab (Callinectes Sapidus): Relationships between Apparent Net H+ Excretion, Calcium and Bicarbonate

1985 ◽  
Vol 119 (1) ◽  
pp. 275-285
Author(s):  
JAMES N. CAMERON
Keyword(s):  
Blue Crab ◽  
Calcium Transport ◽  
Time Course ◽  
Callinectes Sapidus ◽  
Direct Coupling ◽  
Acid Base ◽  
External Concentration ◽  
External Ph

In the days immediately after moulting, manipulations of external pH, [HCO3−], and [Ca2+] were used to determine the nature of the rapid net Ca2+ influx and attendant apparent net H+ efflux in the blue crab (Callinectes sapidus Rathbun). Both fluxes were strongly inhibited by reductions in external [Ca2+], [HCO3−], or pH. The net Ca2+ influx was reversed at an external concentration of 2.5 mmol l−1, and both fluxes were reversed by reducing the external [HCO3−] to 0.2 mmol l−1. The correlation between net Ca2+ flux and apparent net H+ flux was 0.61 (P<0.01), but the variability and the time course of most experiments indicated that the link was indirect, rather than a direct coupling or cotransport. This conclusion was also borne out by acid-base disturbances that occurred in the low-[Ca2+] treatment. The results are consistent with the hypothesis that inward calcium transport is accompanied by both inward HCO3− transport and outward H+ transport, probably by separate exchanges with ions of like charge such as Na+ and Cl−. Crustecdysone (β-ecdysone) does not appear to be involved in control of these post-moult fluxes and calcification.

scholarly journals D1-like dopamine receptors downregulate Na+-K+-ATPase activity and increase cAMP production in the posterior gills of the blue crab Callinectes sapidus

2014 ◽  
Vol 307 (6) ◽  
pp. R634-R642 ◽  
Author(s):  
Francis B. Arnaldo ◽  
Van Anthony M. Villar ◽  
Prasad R. Konkalmatt ◽  
Shaun A. Owens ◽  
Laureano D. Asico ◽  
...  
Keyword(s):  
Protein Expression ◽  
Atpase Activity ◽  
Dopamine Receptors ◽  
Blue Crab ◽  
Callinectes Sapidus ◽  
Basolateral Membrane ◽  
Camp Production ◽  
Degenerate Primers ◽  
Α Subunit ◽  
Low Salinity

Dopamine-mediated regulation of Na+-K+-ATPase activity in the posterior gills of some crustaceans has been reported to be involved in osmoregulation. The dopamine receptors of invertebrates are classified into three groups based on their structure and pharmacology: D1- and D2-like receptors and a distinct invertebrate receptor subtype (INDR). We tested the hypothesis that a D1-like receptor is expressed in the blue crab Callinectes sapidus and regulates Na+-K+-ATPase activity. RT-PCR, using degenerate primers, showed the presence of D1βR mRNA in the posterior gill. The blue crab posterior gills showed positive immunostaining for a dopamine D5 receptor (D5R or D1βR) antibody in the basolateral membrane and cytoplasm. Confocal microscopy showed colocalization of Na+-K+-ATPase and D1βR in the basolateral membrane. To determine the effect of D1-like receptor stimulation on Na+-K+-ATPase activity, intact crabs acclimated to low salinity for 6 days were given an intracardiac infusion of the D1-like receptor agonist fenoldopam, with or without the D1-like receptor antagonist SCH23390. Fenoldopam increased cAMP production twofold and decreased Na+-K+-ATPase activity by 50% in the posterior gills. This effect was blocked by coinfusion with SCH23390, which had no effect on Na+-K+-ATPase activity by itself. Fenoldopam minimally decreased D1βR protein expression (10%) but did not affect Na+-K+-ATPase α-subunit protein expression. This study shows the presence of functional D1βR in the posterior gills of euryhaline crabs chronically exposed to low salinity and highlights the evolutionarily conserved function of the dopamine receptors on sodium homeostasis.

The relationship between blood PH, ammonia excretion and adaptation to low salinity in the blue crab callinectes sapidus

1976 ◽  
Vol 195 (1) ◽  
pp. 129-136 ◽  
Author(s):  
C. P. Mangum ◽  
S. U. Silverthorn ◽  
J. L. Harris ◽  
D. W. Towle ◽  
A. R. Krall
Keyword(s):  
Blue Crab ◽  
Callinectes Sapidus ◽  
Ammonia Excretion ◽  
Low Salinity ◽  
Blood Ph ◽  
The Relationship

scholarly journals Acid-Base Balance in Callinectes Sapidus During Acclimation from High to Low Salinity

1982 ◽  
Vol 101 (1) ◽  
pp. 255-264 ◽  
Author(s):  
RAYMOND P. HENRY ◽  
JAMES N. CAMERON
Keyword(s):  
Carbonic Anhydrase ◽  
Blue Crab ◽  
Callinectes Sapidus ◽  
Weak Acid ◽  
Strong Ion Difference ◽  
Acid Base Balance ◽  
Acid Base ◽  
Ion Regulation ◽  
Low Salinity ◽  
Base Balance

When transferred from 865 to 250 m-osmol salinity, the blue crab C. sapidus maintains its blood Na+ and Cl− concentrations significantly above those in the medium. When branchial carbonic anhydrase is inhibited by acetazolamide, ion regulation fails and the animals do not survive the transfer. An alkalosis occurs in the blood at low salinity, indicated by an increase in HCO3− and pH at constant PCO2. The alkalosis is closely correlated with an increase in the Na+-Cl− difference, a convenient indicator of the overall strong ion difference. The contribution of changes in PCO2 to acid-base changes was negligible, but the change in the total weak acid (proteins) may be important. It is suggested that the change in blood acidbase status with salinity is related to an increase in the strong ion difference, which changes during the transition from osmoconformity to osmoregulation in the blue crab, and which is related to both carbonic anhydrase and ionactivated ATPases. Note:

Sustaining olfaction at low salinities: evidence for a paracellular route of ion movement from the hemolymph to the sensillar lymph in the olfactory sensilla of the blue crab Callinectes sapidus

2000 ◽  
Vol 301 (3) ◽  
pp. 423-431 ◽  
Author(s):  
Richard A. Gleeson ◽  
Lorraine M. McDowell ◽  
Henry C. Aldrich ◽  
Katherine Hammar ◽  
Peter J. S. Smith
Keyword(s):  
Blue Crab ◽  
Callinectes Sapidus ◽  
Olfactory Sensilla ◽  
Ion Movement

scholarly journals Apparent H+ Excretion and CO2 Dynamics Accompanying Carapace Mineralization in the Blue Crab (Callinectes Sapidus) Following Moulting

1985 ◽  
Vol 114 (1) ◽  
pp. 181-196 ◽  
Author(s):  
James N. Cameron ◽  
Chris M. Wood
Keyword(s):  
Blue Crab ◽  
Sea Water ◽  
Callinectes Sapidus ◽  
Dry Weight ◽  
The Body ◽  
Co2 Uptake ◽  
Fluid Compartment ◽  
Bicarbonate Uptake ◽  
Wet Weight ◽  
Co2 Dynamics

Just after moulting the blue crab, Callinectes sapidus, is soft and defenceless, but in the following days, a hard calcareous shell is formed for support and protection. The carapace of intermoult (hard) crabs constitutes 27% of the wet weight and 53% of the dry weight, with 14% of the body water contained in a carapace fluid compartment. The pH of the shell fluid compartment is maintained at 0.3 to 0.5 pH units above that of the blood. The mineral portion of the carapace is primarily CaCO3, with minor components of Mg2+ and PO4−3 plus traces of other ions. The formation of a new shell after moulting is accomplished by apparent H+ excretion and Ca2+ uptake at remarkable rates, averaging 12.5 and reaching as high as 21 mequiv kg−1 h−1. Direct bicarbonate uptake from the sea water appears to be an important component of the apparent H+ efflux, since CO2 is deposited in CaCO3 at a rate greater than metabolic production, and the animals show a net CO2 uptake for several days.

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