Eicosanoid involvement in the regulation of behavioral fever in the desert locust, Schistocerca gregaria

Abstract

The desert locust Schistocerca gregaria behaviorally thermoregulates in order to try and maintain a favoured "set point" body temperature. Locusts infected with the deuteromycete fungal pathogen Metarhizium anisopliae var acridumchoose a significantly elevated temperature. This "behavioral fever" greatly delays the progress of mycosis. We have confirmed this phenomenon and shown that desert locusts also fever when infected with the bacterial pathogen Serratia marcescens. Elevation in the prefered environmental temperature occurs also upon injection with laminarin and lipopolysaccharide (microbial cell wall components). Since such treatments also stimulate the immune system it would appear that "behavioral fever" is probably a feature of the immune response. The eicosanoid biosynthesis inhibitor dexamethasone prevented laminarin invoked fever. This effect was reversable by arachidonic acid. Therefore in common with the febrile response in mammals behavioral fever in insects may be mediated locally by circulating eicosanoids.

Prostaglandins A1 and E1 influence gene expression in an established insect cell line (BCIRL-HzAM1 cells)

“…In the case of PGE, for example, there are four receptor subtypes EP1-EP4 (Gobeil et al, 2003). The cellular actions driven by these receptors can lead to short-term changes in homeostatic physiology, such as induction of fever (Ushikubi et al, 1998) [true also for insects, as seen in locusts (Bundey et al, 2003)], smooth muscle contraction (or relaxation) (Moreland et al, 2003) or hemodynamic effects (Audoly et al, 1999). PGs also influence gene expression in many mammalian systems.…”

Eicosanoid Actions in Insect Immunity

“…In the case of PGE, for example, there are 4 receptor subtypes, EP1-EP4 [60] . The cellular actions mediated by these receptors influence homeostatic physiology, such as induction of fever [62] -true also for insects, as noted earlier [46] -and smooth muscle contraction (or relaxation) [63] . PGs also influence gene expression in many mammalian systems.…”

“…Behavioral fevers are sufficiently efficacious that they have practical implications in the application of pathogenic fungus in locust biocontrol programs [45] . Adult males of the locust Schistocerca gregaria generate febrile responses to infection by the fungus M. anisopliae and by the bacterium Serratia marcescens [46] . Bundey et al [46] found the fever induced by laminarin is mediated by eicosanoids.…”

“…Adult males of the locust Schistocerca gregaria generate febrile responses to infection by the fungus M. anisopliae and by the bacterium Serratia marcescens [46] . Bundey et al [46] found the fever induced by laminarin is mediated by eicosanoids. We infer from these findings that eicosanoids are involved in at least 2 lines of defense against fungal infection, the cellular defense of nodulation and the febrile defense of increasing host body temperatures to a nonpermissive level for the fungus.…”

Confronting physiology: how do infected flies die?

“…Pain thresholds and changes in grooming or irritability have not been assayed in response to infection, but suitable assays exist. Fever occurs in many insects, and this happens at both the individual and community level (Louis et al, 1986;Adamo, 1998;Starks et al, 2000;Bundey et al, 2003). The only fevers measured so far in insects are behavioural; for example, these insects can thermoregulate by positioning themselves at warmer temperatures when they are infected, just as we might sit near the fire.…”