Tracheal Respiration in Insects Visualized with Synchrotron X-ray Imaging

Abstract

Insects are known to exchange respiratory gases in their system of tracheal tubes by using either diffusion or changes in internal pressure that are produced through body motion or hemolymph circulation. However, the inability to see inside living insects has limited our understanding of their respiration mechanisms. We used a synchrotron beam to obtain x-ray videos of living, breathing insects. Beetles, crickets, and ants exhibited rapid cycles of tracheal compression and expansion in the head and thorax. Body movements and hemolymph circulation cannot account for these cycles; therefore, our observations demonstrate a previously unknown mechanism of respiration in insects analogous to the inflation and deflation of vertebrate lungs.

The evolutionary consequences of oxygenic photosynthesis: a body size perspective

“…The latter interpretation is suggested by the fact that all of the largest Paleozoic specimens belong to the Protodonata; Paleozoic members of the Odonata exhibit sizes comparable to the largest in the Mesozoic and Cenozoic. Alternatively, the simplifying assumption of oxygen diffusion through tracheae may be inaccurate; there is emerging evidence for active tracheal breathing in insects (Socha et al 2008;Westneat et al 2003). Okajima (2008) proposed still another alternative: although variation in oxygen may have contributed to size evolution, maximum size of Mesozoic and Cenozoic dragonflies was limited by ecological competition with flying vertebrates.…”

Terrestrial Insects with Tracheae Breath by Actively Regulating Ventilatory Movements: Physiological Similarities to Humans

“…This statement conflicts with the widely used diffusional theory of insect respiration, which was created almost 100 years ago (Krogh 1920). Due to the lack of experimental data, the theory has persisted as the main model of insect respiration until this time (Krogh 1941;Lighton 1996Lighton , 2008Wasserthal 1996;Nation 2002;Marais et al 2005;Westneat 2003Westneat , 2008Chown et al 2006;Hetz and Bradley 2005;Contreras and Bradley 2009;Aboelkassem and Staples 2013;Klowden 2017). Our results corroborate previous findings of Sláma (1984,1988,1999,2010), which provided experimental evidence that large or small insects actively ventilated the tracheal system by the mechanical inhalation or exhalation of air through selected spiracles.…”

“…Another technical improvement in insect respiration was the synchrotron xray imaging of tracheal movements (Westneat et al 2003). These movements were first observed by Babák (1921), later confirmed by Herford (1938) in the flea, Xenopsylla cheopis, and in other insects (reviewed by Wigglesworth 1947, Kuznetzoff 1953.…”

“…Respirometric data obtained by techniques other than the IR CO2 analysis, such as differential (CO2-O2) gaseous exchange in small insects and ticks (Sláma 1988(Sláma , 1999Sláma et al 2007;Sláma and Jedlička 2012), which also exhibited enormous bursts of CO2, remained unknown or were considered unimportant. Finally, new results on the movement inside the tracheal system were obtained from X-ray, cyclotron studies by Westneat et al (2003Westneat et al ( , 2008 and Socha et al (2010), which adhered in their studies to the diffusion concept of Lighton (1996). The most recent study on insect respiration (Aboelkassem and Staples 2013) is based on the data of Westneat et al (2008).…”

“…The movements of the tracheal system inside the body was observed by Herford (1938) in the transparent body of a flea Xenopsylla cheopis. More recently, distinctive tracheal movements in adult beetles were found by the method of X-ray cyclotron imaging (Westneat et al 2003(Westneat et al , 2008Socha et al 2010). …”