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

Richard A. Gleeson, Michele G. Wheatly, Carl L. Reiber

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

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 aesthetases 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.

Original languageEnglish (US)
Pages (from-to)445-456
Number of pages12
JournalJournal of Experimental Biology
Volume200
Issue number3
StatePublished - Feb 1 1997
Externally publishedYes

Keywords

  • Aesthetasc
  • Blue crab
  • Callinectes sapidus
  • Dendrites
  • Olfaction
  • Osmotic effects
  • Perireceptor mechanisms
  • Salinity

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Insect Science

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