Metabolic transformations of acquired lucibufagins by firefly “femmes fatales”

Abstract

Female Photuris fireflies sequester defensive steroidal pyrones (lucibufagins) from male fireflies of the genus Photinus. Lucibufagin analyses of Photuris females and Photinus ignitus males show that the lucibufagin mixtures of predator and prey differ in their composition. Analyses of whole body extracts showed that P. ignitus males contain a mixture of eight non-glycosylated lucibufagins, composed mostly of compounds with two oxygenated positions in the steroidal A-ring (C-3, C-5). After feeding on P. ignitus males, Photuris females contain six major lucibufagins. Three of these compounds are not present in the prey, including the novel lucibufagin glycoside 5i,11h-dihydroxy-12-oxo3i-O-i-D-xylopyranosylbufalin, and two other lucibufagins with a trioxygenated A-ring (C-2, C-3, C-5).These results indicate that Photuris females transform the sequestered lucibufagins both by glycosylation and oxidation, which could affect the systemic transportability of these compounds due to an increase in their polarity.

Chemical egg defense in Photuris firefly "femmes fatales"

“…The laboratory-reared Photuris (males and females) were raised from field-collected larvae following procedures described elsewhere (Eisner et al 1997;González et al 1999a). The larvae were collected in their late instars, on soil, at night in early fall, and kept in the dark at 10°C until May.…”

“…Injection volume was 25 ml, the flow was 1 ml/min, and the analyses were monitored at u =300 and 325 nm for quantification of the individual lucibufagins and the betaine, respectively. A pure sample of the lucibufagin 3-O-acetyl-5i,11h-dihydroxy-12-oxobufalin, isolated from P. ignitus (González et al 1999a), and a synthetic sample of the betaine (prepared according to Quast & Schmitt 1970), were used to construct the calibration curves for the HPLC analysis, using coumarin as internal standard. The curves correlated the net amounts of both the lucibufagin and betaine standards with the ratios of the chromatographic peak areas of each compound and that of the internal standard.…”

“…The corresponding coefficients used in the analysis of Photuris adults and larvae were 0.992 and 0.999. Since the lucibufagin in Photuris is present as a mixture of related compounds (González et al 1999a), the total quantity of lucibufagin was calculated as the sum of individual lucibufagin components.…”

“…1A), but their content is minimal unless they fed on Photinus (Eisner et al 1997;González et al 1999a). Specifically, female Photuris respond to the flash signals of Photinus males by emitting light pulses imitative of those of Photinus females, thereby luring the Photinus males to within graspable range.…”

Dietary sequestration of defensive steroids in nuchal glands of the Asian snake Rhabdophis tigrinus

“…2 and 5). Hydroxylation of sequestered dietary toxins has been reported in predacious fireflies (28) and dendrobatid frogs (7). In dendrobatids, hydroxylation dramatically increases the toxicity of a sequestered alkaloid (7).…”