01524nas a2200157   4500008004100000245012800041210006900169260000800238300001000246490000800256520099900264100002001263700002101283700001801304856004401322       2004                        eng d00aMorphometric analysis of the larval branchial chamber in the dragonfly Aeshna cyanea Müller (Insecta, Odonata, Anisoptera)0 aMorphometric analysis of the larval branchial chamber in the dra  cJul  a81-910 v2613 aThe aquatic larvae of anisopteran dragonflies possess tracheal gills located in the rectum. Using stereological methods, we estimated the morphometric diffusing capacity for oxygen (D(MO2)) across the gill epithelium, i.e., from rectal water to the gill tracheoles, in the larvae of Aeshna cyanea. A 271-mg larva has a total branchial surface area of approximately 12 cm(2). Tracheoles make up 6% of the epithelial volume of the gills; the harmonic mean thickness of the water-tracheolar diffusion barrier is 0.27 microm and consists mainly of cuticle. The calculated D(MO2) is 23.0 microl min(-1) g(-1) kPa(-1), which, using published values for oxygen consumption in a similar species, would result in a mean driving pressure of 0.2 kPa at rest and 1.3 kPa during activity. Since these driving pressures are similar to those reported for other arthropods, we conclude that the D(MO2) of the gill is not rate-limiting for aerobic metabolism in Aeshna cyanea larvae. J Morphol. 261:81-91, 2004.1 aKohnert, Stefan1 aPerry, Steven, F1 aSchmitz, Anke  uhttps://odonatas.myspecies.info/node/61