Intraspecific variation in tracheal volume in the American locust, Schistocerca americana, measured by a new inert gas method

Hilary M. Lease, Blak O. Wolf, Jon Harrison

Research output: Contribution to journalArticle

39 Scopus citations

Abstract

The volume of a tracheal system influences breath-holding capacity and provides an index of an insect's investment in its respiratory system. Here, we describe a new, generally applicable method to measure tracheal volume that enables repeatable determinations on live animals. Animals are isolated in a closed chamber of a known volume and equilibrated with a helium:oxygen gas mixture. The chamber is then rapidly flushed with a ni trogen: oxygen gas mixture to eliminate the helium surrounding the animal, and sealed. After a period of time sufficient to allow equilibration of helium between tracheal system and chamber air, a gas sample is taken from the chamber, and tracheal volumes are calculated from the helium content of the sample, using a gas chromatograph. We show that relative investment in the tracheal system increases with age/size in the grasshopper; tracheal volume scales with mass to the power 1.3. This increased proportional investment in the tracheal system provides a mechanistic basis for the enhanced respiratory capacity of older grasshoppers. Tracheal volumes decrease strongly as grasshoppers grow within an instar stage, explaining reduced safety margins for oxygen delivery. Finally, tracheal volumes are smaller in gravid females than males, probably due to compression of air sacs by eggs.

Original languageEnglish (US)
Pages (from-to)3476-3483
Number of pages8
JournalJournal of Experimental Biology
Volume209
Issue number17
DOIs
StatePublished - Sep 1 2006

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Keywords

  • American locust
  • Respiration
  • Scaling
  • Schistocerca americana
  • Trachea

ASJC Scopus subject areas

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

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