Origin, transfer and distribution of cantharidin-related compounds in the blister beetle Hycleus scabiosae

Abstract

Cantharidin provides chemical protection for the coleopteran families Meloidae and Oedemeridae. In the present study, it was observed that cantharidin concentration in Hycleus scabiosae was slightly decreased from mated females (mean = 0.011 mg/mg of dry weight) to males (mean = 0.010 mg/mg) and considerably diminished in relation to virgin females (mean = 0.005 mg/mg). Significant concentrations of palasonin (21.69 ng/mg among virgins and 17.49 ng/mg in mated females) and palasoninimide (14.62 ng/ mg in virgins and 9.17 ng/mg in mated females) were found in H. scabiosae. Palasonin, palasoninimide and cantharidinimide content of eggs were measured as 5.61, 7.69 and 7.80 ng/mg respectively. Surprisingly, males showed no trace of cantharidin-related compounds (CRCs); therefore CRCs in H. scabiosae could not be transferred from males to females and based on experiments employing its deuterated form, cantharidin is probably independently synthesized in females from the male nuptial transfer. An inseminated female incorporates about 38.5 ng of cantharidin (0.34% of the maternal content), 196.35 ng of palasonin (91.82% of maternal content) and 269.15 ng of palasoninimide (96.70% maternal content) into each egg mass during oviposition. It seems that eggs of this meloid species exploit a different array of protective chemicals by increasing the ratio of CRCs versus cantharidin. CRCs are less toxic than cantharidin; therefore, such compounds might have been deposited in eggs as a safer substitute for cantharidin to provide effective protection, but does not simultaneously harm the susceptible embryo.

Cantharidin content in two Mediterranean species of blister beetles, Lydus trimaculatus and Mylabris variabilis (Coleoptera: Meloidae)

“…the male accessory glands; Jiang et al 2017). However, the lack of a significant difference between sexes when comparing individuals randomly collected from the field could be due to the CA transfer by males to females during copulation, which would increase the total CA reserve in mated females (Sierra et al 1976;Nikbakhtzadeh et al 2012).…”

“…Hence, CA is supposed to have a primary defensive role, but also to be involved in reproduction. In fact, males of meloid beetles usually produce more CA than females (Capinera et al 1985;Blodgett et al 1991;Carrel et al 1993;Nikbakhtzadeh & Tirgari 2002;Mebs et al 2009;Bravo et al 2017) and transfer large quantities of this terpene to females during copulation (Selander 1964;Bologna 1991;Carrel et al 1993;Dettner 1997;Nikbakhtzadeh 2004;Nikbakhtzadeh et al 2012). Females are supposed to use the transferred CA for covering eggs to protect them from potential predators (Sierra et al 1976;Carrel et al 1993;Eisner et al 2002).…”

“…because these are supposed to be responsible for poisoning livestock feeding on alfalfa hay contaminated with CA (Capinera et al 1985;Blodgett et al 1991Blodgett et al , 1992Carrel et al 1993;Blodgett & Denke 1999). In contrast, apart from some pioneering approaches (reported in Beauregard 1890), few investigations have been undertaken on other species, with sparse data on CA content only available for few other members of the subfamily Meloinae, primarily collected in Iran, South Africa (Nikbakhtzadeh & Tirgari 2002;Mebs et al 2009;Nikbakhtzadeh et al 2012) and, more recently, in the Iberian Peninsula (Bravo et al 2017).…”

Cantharidin world in nature: a concealed arthropod assemblage with interactions via the terpenoid cantharidin

“…They acquire the compound from males through frequent copulation and use it subsequently for defending eggs (Nikbakhtzadeh et al . , ). In contrast, both sexes of oedemerid beetles produce cantharidin in their bodies (Carrel et al .…”

The Potential Organ Involved in Cantharidin Biosynthesis in Epicauta chinensis Laporte (Coleoptera: Meloidae)

“…Blister beetles are famous for its defensive compound, cantharidin, which is highly toxic to most animals ( Dettner 1997 , Ghaffarifar 2010 , Khan et al 2013 ). Cantharidin is a widely known insect defensive product or a sexual attractant and stimulates copulation in Epicauta nyassensis (Coleoptera: Meloidae) ( Nikbakhtzadeh et al 2007a , b , 2012 ). Moreover, cantharidin has only been found in blister beetles (Coleoptera: Meloidae) and oedemerid beetles (Coleopetra: Oedemeridae), where it is found in various tissues ( Carrel et al 1986a , Frenzel and Dettner 1994 , Dettner 1997 ).…”