Anti-aphrodisiac pheromone, a renewable signal in adult butterflies

Abstract

The male butterfly Pieris napi produces the anti-aphrodisiac pheromone methyl salicylate (MeS) and transfers it to the female during mating. After mating she releases MeS, when courted by conspecific males, which decreases her attractiveness and the duration of male harassment, thus increasing her time available for egg-laying. In previous studies we have shown that males produced MeS from the amino acid L-phenylalanine (L-Phe) acquired during larval stage. In this study we show that adult males of P. napi can utilize L-Phe and aromatic flower volatiles as building blocks for production of anti-aphrodisiac pheromone and transfer it to females during mating. We demonstrate this by feeding butterflies with stable isotope labelled molecules mixed in sugar solutions, and, to mimic the natural conditions, we fed male butterflies with floral nectar of Bunias orientalis plants treated with labelled L-Phe. The volatiles from butterflies and plants were collected and identified by solid phase micro extraction, gas chromatography and mass spectrometry techniques. Since P. napi is polygamous, males would gain from restoring the titre of MeS after mating and the use of aromatic precursors for production of MeS could be considered as an advantageous trait which could enable butterflies to relocate L-Phe for other needs.

The scent chemistry of butterflies

“…Larval feeding experiments with the labelled l -phenylalanine proved that 48 is only produced by males 99 and taken up in the adult stage. 179 Behavioural assays demonstrated that mated females, but also virgins perfumed with 48 , are quickly abandoned by courting males, while females lacking 48 are more attractive. 97 Remating can be observed after 4–6 days.…”

“…203 While terpene secretions discourage attacks by ants, acid production is rendering the caterpillars less palatable. 204 In several species of the heterogeneous group the h instar secretion was found to contain 2-methylpropanoic acid (178) and 2-methylbutanoic acid (181) as major constituents, together with their methyl (179,182) and ethyl esters (180, 183, Fig. 37).…”

Post mating isolating barriers between Drosophila species and the role of seminal fluid gene expression

“…Mate guarding can persist even when the male is not physically present. This happens when antiaphrodisiac pheromones are transferred to the female, which makes her unattractive to other males (Mozuraitis et al, 2019). A similar process is the formation of a mating plug, which is the result of the coagulated male's ejaculate that blocks the female's reproductive tract and prevents sperm from rival males to enter the sperm storage organs (Polak et al, 2001).…”