Ontogenic synchronization of Bephratelloides cubensis, Annona macroprophyllata seeds and acetogenins from Annonaceae.

ABSTRACT

The seeds of Annona macroprophyllata Donn. Sm. contain idioblasts with toxic acetogenins, including laherradurin and rolliniastatin-2, in relatively high proportions. Both metabolites are cataloged as potent insecticides for several species, even so, the wasp Bephratelloides cubensis Ashmead fulfills almost its entire life cycle inside the seeds of this and other annonaceous species, to such a degree, that they constitute a strong selection pressure. In order to document the chemical relationship between the two species, it is reported for the first time in this paper the presence of idioblasts and acetogenins during the ontogenic development of the seeds of A. macroprophyllata, and contrasted with the development of B. cubensis. The results indicate that idioblasts with laherradurin and rolliniastatin-2 acetogenins are formed in the middle stages of the endospermic development, also that both acetogenins are biosynthesized simultaneously, and that their proportion is dependent on the degree of development. The acetogenins are present in high amounts that suppose a sufficient toxic barrier and, in this case, laherradurin is the most abundant (> 1000 µg g dry weight-1). The wasp B. cubensis only emerges from the seeds to copulate and returns for oviposition; its larval phase coincides with the appearance of acetogenins, so it feeds on the acetogenic endosperm. The absence of acetogenins in the tissues and excreta of the insect supposes a metabolization of the molecules, which would explain the tolerance to its toxicity.