Differential Utilization of Pyrrolizidine Alkaloids by Males of a Danaid Butterfly, Parantica sita, for the Production of Danaidone in the Alar Scent Organ

Abstract

Males of the chestnut tiger butterfly, Parantica sita, secrete danaidone as a major component from the alar androconial organ (sex brand). Since danaidone has been postulated to be derived from various pyrrolizidine alkaloids (PAs), which males ingest as adults from PA-containing plants, we conducted oral administration tests of several PAs to examine their availability for danaidone production by P. sita males. Males fed with a mixture of intermedine (80%) and lycopsamine (20%) produced danaidone at an average of 25.7 μ g per individual, which was comparable to that found in field-caught males. In contrast, a smaller amount of danaidone (5.7 to 7.0 μg/male) was formed when males ingested retronecine or heliotrine, and those fed with an HCl salt of monocrotaline or retrorsine produced only traces of danaidone (< 0.5 μ g/male). In addition, males showed a strong feeding response to intermedine/lycopsamine, whereas the other PAs elicited no positive feeding behavior. These results indicate that, unlike the arctiid moths, P. sita males can only successfully convert limited chemical types of PAs into danaidone, and further suggest that in the field, males selectively ingest particular PAs that are readily transformable into danaidone.