Comparison of Age-dependent Quantitative Changes in the Male Labial Gland Secretion of Bombus Terrestris and Bombus Lucorum

Abstract

-Quantity of components of the labial gland secretion of bumblebee males changes significantly during ageing of males. In B. terrestris, compounds showing the EAG-activity to virgin queens are ethyl dodecanoate, 2,3-dihydrofarnesal, 2,3-dihydrofarnesol, hexadecanol, octadeca-9,12,15-trienol, and geranylcitronellol. The EAG-active compounds found in B.lucorum are ethyl dodecanoate, ethyl tetradec-7-enoate, ethyl tetradec-9-enoate, ethyl hexadec-9-enoate, hexadecanol, hexadec-7-enal, octadeca-9,12-dienol, octadeca-9,12,15-trienol and octadecanol. Quantification of these compounds based on a calibration showed that the main components were present in milligram amounts in both species. Different concentration pattern of active compounds was observed in the species studied. Compounds reached maximal amounts about seventh day after eclosion. Then, a rapid concentration decrease occurs in B. terrestris whereas the amounts of active compounds stay approximately constant or decreases only slowly in B. lucorum. These results were also confirmed by means of optical microscopy. B. terrestris secretory cells undergo apoptosis since the fifth to the tenth day of life, whilst they live and show secretory activity through the whole life of B. lucorum males.

Scent of a break-up: phylogeography and reproductive trait divergences in the red-tailed bumblebee (Bombus lapidarius)

“…The MMS consist of a complex mixture (mainly aliphatic compounds) with several major components and with intraspecific variation (e.g. [33,34]). MMS are produced de novo by cephalic labial glands [35] from saturated fatty-acids by the action of species-specific esterases, desaturases and reductases in cephalic labial glands [35,36].…”

Changes in the Composition of Triacylglycerols in the Fat Bodies of Bumblebee Males During Their Lifetime

“…Assuming energy efficiency in nature, it seems to be unnecessary for bumblebees to invest in an enzymatic system producing the sex-pheromone component in the gland if a large pool of precursors has been produced already. The amounts of the pheromone stored in the gland are huge when compared to Lepidoptera (several milligrams per gland as reported by Ž áček et al [15]). Lepidopteran sex pheromones have double-bond positions, and their configuration is different from the fat lipids [33,34].…”

“…These changes must be based on the males' physiology, as their diet was a standard one, identical in both species and in all age classes. B. terrestris and B. lucorum males differ in the temporal dynamics of the physiological activity of the pheromone gland and consequently in the time-related production of the marking pheromone [14,15]. While in B. terrestris the pheromone is produced up to the fifth day of a male's life and then stored in the gland, in B. lucorum the pheromone biosynthesis goes on for the male's entire life.…”

“…The freshly emerged males were removed and kept according to age. Animals of the following age were studied: Bombus terrestris: shortly after eclosion, 1, 2, 3, 4, 5, 7, 10, 12, and 24 days after eclosion (5 individuals of each age); B. lucorum: shortly after eclosion, 1,2,3,4,5,6,7,8,9,10,15,20,25, and 30 days after eclosion (5 individuals of each age). The males were killed by freezing (-18°C) and kept frozen prior to dissection.…”

“…On the other hand, the male-marking pheromone of these species differs in its main components and only medium or minor components are shared [12,13]. Furthermore, the dynamics in the pheromone production differ greatly; in B. terrestris, the pheromone is formed only during the first 5 days and stored for the rest of the male's life, whereas in B. lucorum the biosynthesis goes on for the male's entire life [14,15]. In connection with our hypothesis on pheromone formation from lipidic precursors, the different ontogeny of the pheromonal gland in these closely related species raised the question of whether the fat bodies will follow a similar pattern.…”