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

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.

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.

Foraging behavior of an estuarine predator, the blue crab Callinectes sapidus in a patchy environment

Ecography ◽  
2000 ◽  
Vol 23 (1) ◽  
pp. 21-31 ◽  
Author(s):  
Mary E. Clark ◽  
Thomas G. Wolcott ◽  
Donna L. Wolcott ◽  
Anson H. Hines
Keyword(s):  
Foraging Behavior ◽  
Blue Crab ◽  
Callinectes Sapidus ◽  
Patchy Environment
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