Intraspecific transfer of cantharidin within selected members of the family Meloidae (Insecta: Coleoptera)

The use of deuterium-labelled cantharidin (CAN-D2) to study details of cantharidin transfer in blister beetles indicates that the dynamics of organ-selective cantharidin accumulation may differ over time. Although the accessory glands absorb a high amount of CAN-D2 in the short term, they ultimately accumulate less than the testes. Confirming previous studies, the last steps in the pathway of biosynthesis of cantharidin occur in the male's body distantly from the reproductive system but the ultimate product, cantharidin, is transported into the male reproductive tract via the membrane of the accessory glands. From there it first transfers preferentially to the epididimis and the vas deferens, followed by final deposition in the testes. Most, if not all, of the cantharidin passes internally within the sexual organs; hemolymph transport is not involved. In female meloids, cantharidin enters the genitalia from the male as a nuptial gift. High amounts are first absorbed by the spermatophoral receptacle followed by spreading through the ovaries and an ultimate accumulation in the eggs. The amount taken up by the ovaries remains considerably lower than that of the receptacle. Over time these two organs stop accumulating cantharidin, while the bursa copulatrix starts to incorporate the gift actively. The accumulated amount taken up by bursa is mainly supplied by the receptacle and ovaries suggesting that an internal transfer of cantharidin is used in females as the main transport route.