Selective sequestration of milkweed (Asclepias sp.) cardenolides inOncopeltus fasciatus (Dallas) (Hemiptera: Lygaeidae)

Abstract

The cardenolide content of the gut, wings, and fat body ofOncopeltus fasciatus was examined. The female fat body contained 4-5% of the total cardenolide content of the insect. The cardenolide content of male fat body, and gut and wings of both sexes was below the detection limit of the cardenolide assay. Thin-layer chromatography was used to determine the cardenolide array of various tissues and secretions ofO. fasciatus reared on seeds of a single species of milkweed (A. Speciosa) and adult extracts and dorsolateral space fluid ofO. fasciatus reared on seeds of two species of milkweed with different cardenolide arrays (A. speciosa andA. syriaca). Our results indicate that cardenolides are not sequestered in the insect simply on the basis of polarity and that metabolism and differential excretion of cardenolides are involved in the sequestration of cardenolides inO. fasciatus. The similarities in the cardenolide profiles ofO. fasciatus reared on different food sources, and tissues ofO. fasciatus reared on a single food source indicates that there is regulation of the cardenolide array inO. Fasciatus.

Cardenolide content, emetic potency, and thin-layer chromatography profiles of monarch butterflies,Danaus plexippus, and their larval host-plant milkweed,Asclepias humistrata, in Florida

“…Nevertheless, like the monarch these conspicuously coloured species also sequester milkweed cardenolides as effective defenses against natural enemies (Duffey & Scudder 1972Isman et al 1977, Duffey et al 1978Scudder & Meredith 1982;Scudder et al 1986;Malcolm 1990Malcolm , 1992. However, because these hemimetabolous insects can also feed on different milkweed species as adults it may not be possible to use host plant-derived cardenolide fingerprints to describe their patterns of movement as in the holometabolous monarch (Moore & Scudder 1985;Malcolm 1990Malcolm , 1992Malcolm et al 1992). Seiber et al (1980) first suggested that monarchs sequester cardenolides more efficiently from plants with low concentrations.…”

Plant chemistry and insect sequestration

“…Oncopeltus fasciatus bugs concentrate CGs mainly from seeds, rather than from leaves ). Most of the CGs are stored in the dorsolateral space, a vacuolated and pigmented epidermal cell layer (Scudder and Meredith 1982a), whereas very low concentrations of CGs are detectable in the haemolymph (Duffey and Scudder 1974;Scudder and Meredith 1982b;Moore and Scudder 1985). The storage of more polar CGs occurs from the first larval instar through to the adult stage, after at least partial conversion of non-polar CGs to more polar metabolites (Duffey et al 1978;Scudder and Meredith 1982b;Moore and Scudder 1985).…”

Cardenolides from Gomphocarpus sinaicus and Pergularia tomentosa (Apocynaceae: Asclepiadoideae) deter the feeding of Spodoptera littoralis

“…Insects feeding on cardenolidecontaining plants are either behaviourally (Helmus and Dussourd 2004) or physiologically adapted (Vaughan and Jungreis 1977;Moore and Scudder 1985;Scudder et al 1986) to deal with cardenolides and often accumulate them in their tissues as an acquired chemical defence against vertebrate predators (for example, Rothschild 1972;Martel and Malcolm 2004).…”