Topical application of Pya‐AKH stimulates lipid mobilization and locomotion in the flightless bug, Pyrrhocoris apterus (L.) (Heteroptera)

Abstract

Abstract. Two different methods of applying Pya-AKH to long-winged (macropterous) females of the firebug, Pyrrhocoris apterus (Linnaeus) (Heteroptera) were compared: both injection and topical application increased the levels of lipids in the haemolymph and stimulated locomotor activity. Lipid mobilization was maximal when 10 pmol was applied by injection or 40±100 pmol by topical application, with the first significant responses occurring 1.5 h after injection and 2 h after topical application. The highest elevations of lipid concentration in the haemolymph were comparable between the treatments, i.e. 14.36 AE 3.59 mg=mL for injection and 14.43 AE 4.07 mg=mL for topical application. However, these maximal elevations were achieved at different times: 3 h after the injection and 7 h after the topical application.Injection of 10 and 40 pmol of Pya-AKH stimulated locomotor activity with maximal activity 3 h later but, surprisingly, injection of 80 pmol showed no effect initially and than a slight inhibitory effect after 6±8 h.Increased locomotor activity was found after topical application of Pya-AKH, but the response was lower than after injection and appeared later, 5±9 h after the hormone application. In addition, the greatest increase in walking activity required topical application of 300 pmol and was still less dramatic than the response to injection. The stimulatory effect of Pya-AKH on locomotion was positively correlated with its effect on lipid mobilization only for injection of the hormone. It is argued that a stress caused by injection could play a role in the appearance of the complex response to adipokinetic hormone.

Energy Homeostasis Control in Drosophila Adipokinetic Hormone Mutants

“…This view is supported by many studies describing correlations between the release of AKH and activities like flight and walking (Lorenz 2003), and on experimental increase of locomotion, such as walking of the firebug Pyrrhocoris apterus, by ectopic applications of AKH (Kodrík et al 2000(Kodrík et al , 2002. Ablation of CC cells in Drosophila decreased spontaneous locomotion (Isabel et al 2005).…”

Do long- and short-winged adult females of the bug Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae) differ in lifespan and reproductive capacity?

“…The longevity of D. melanogaster is also extended by transgenic over-expression of the insulin signalling responsive transcription factor encoded by dFOXO in the fat body (Ginnakou et al, 2004;Hwangbo et al, 2004). However, it must be pointed out that AKHs, the hormones regulating mobilizations of energy reserves from the fat body and stimulating locomotion in various insects, including P. apterus (Socha et al, 1999;Kodrík et al, 2002aKodrík et al, ,b, 2010Kodrík, 2008), might be also involved in coordinative endocrine regulation of ageing in insects. Defining the interactions between JH and AKH is likely to be the subject of the next phase in the study of the coordinative endocrine regulation of ageing in P. apterus and D. melanogaster.…”

Corpus allatum volume-dependent differences in accessory gland maturation in long- and short-winged males of Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae)

“…The latter hormone mobilizes lipid reserves from the fat body to supply the energy for the enhanced walking activity of macropterous individuals (Socha et al, 1998;Kodrík et al, 2000). Mobilization of lipids from the fat body and enhanced walking activity of macropterous adults of P. apterus can be stimulated by the injection or topical application of AKH Kodrík et al, 2002). In the milkweed bug Oncopeltus fasciatus, however, it is the JH that is primarily responsible for stimulation and coordination of migratory flight and reproduction, while the corpus cardiacum does not seem to be involved in migratory behaviour of this species (Rankin & Riddiford, 1977).…”