6. Respiration and energetics measurement in honey bees
Respiratory gas exchange is one of the basic physiological mechanisms of insect metabolism. In honey bees, basal or resting metabolism and its temperature dependence (Stabentheiner et al., 2003a; Petz et al., 2004; Kovac et al., 2007), discontinuous gas exchange cycles (Kovac et al., 2007) and energetics of foraging and flying (e.g. Wolf et al., 1989; Harrison and Hall, 1993; Harrison et al., 1996; Woods et al., 2005) have all been investigated so far. Respiratory measurements are also a valuable tool for the determination of (respiratory) critical thermal maxima and minima (CTmax, CTmin) and chill coma temperature (Lighton and Lovegrove, 1991; Lighton and Turner, 2004; Kovac et al., 2007; Käfer et al., 2012). Measurements on tiny honey bee larvae (Petz et al., 2004) however require a different setup than measurements on flying (e.g. Roberts and Harrison, 1999) or thermoregulating bees (Goller and Esch, 1991; Blatt and Roces, 2001; Stabentheiner et al., 2003a, 2012), bee groups (Moritz and Southwick, 1986; Southwick and Moritz, 1985, 1987), or whole bee swarms and colonies (Heinrich, 1981a, b; Southwick, 1985, 1988; Van Nerum and Buelens, 1997; see Heinrich, 1993 for more literature). Metabolic differences exist among stages of honey bee development. They are not just a result of differences in mass, but may reflect the bees' development of mitochondrial capacity and enzymatic make-up, as is the case in the first days after emergence (Hersch et al., 1978; Harrison, 1986; Moritz, 1988). Honey bees are also subjected to environmental variation throughout their life cycle, and measurement of whole-body and whole-colony respiration and heat production can provide insights into respiratory and energetic adaptations to the challenges of environmental variation and contribute to a better understanding of the benefits of social cooperation.
This paper is meant as a short guide into the main concepts and setups of whole-animal and colony respiratory and energetic measurements in honey bees. It cannot, however, provide a complete and detailed description of all possible measuring arrangements. A valuable help for a deeper understanding of the possibilities and limitations of insect respiratory and energetic measurement is given by Lighton (2008). For details on the measurement of cellular and sub-cellular respiration and metabolism good references are Suarez et al. (1996, 2000) and Suarez (2000).
Any company names mentioned herein are meant as a quick help for the reader to find a faster entry into the field. In no way it means that these companies are the only manufacturers of a certain type of device. Furthermore, since such information may change with time, the reader interested such equipment will eventually have to search for more and updated information.