Identification, accumulation, and biosynthesis of the cuticular hydrocarbons of the southern armyworm, Spodoptera eridania (cramer) (lepidoptera: Noctuidae)

Abstract

The accumulation and biosynthesis of cuticular and internal hydrocarbons in the Southern armyworm, Spodoptera eridania, were examined at closely timed intervals during larval and pupal development. Gas chromatography-mass spectrometry (GC-MS) was used to identify n-alkanes, monomethylalkanes, and dimethylalkanes ranging in chain length from 23 to 35 carbons. The amount of cuticular hydrocarbon stayed relatively constant duringeach stadium, while the amount of internal hydrocarbon increased dramatically during the first half of each larval stadium, presumably to replace the cuticular hydrocarbon lost on the shed cast skin with each molt. The accumulation of internal hydrocarbon was mirrored by large increases in the rate of incorporation of labeled acetate into the hydrocarbon fraction. Hydrocarbon production fell to very low rates during the latter part of the fourth and fifth larval stadia. Relatively high rates of hydrocarbon production were observed during the first and last one-third of the pupal stage and essentially all of the hydrocarbons produced during this stage remained internal. These data document large changes in the rates of hydrocarbon production during development in S. eridania and suggest that most of the hydrocarbon produced during each stage was stored internally and then transported to the cuticle of the next stage.

Site of synthesis, tissue distribution, and lipophorin transport of hydrocarbons in Blattella germanica (L.) nymphs

“…Moreover, immatures face a repeated challenge of HC synthesis and deposition onto the new cuticle as they pass through the series of molts (six in female B. germanica) to adulthood. The epicuticle of newly eclosed insects is covered with HC synthesized during the previous stadium (Guo and Blomquist, 1991;Young and Schal, 1997), but the course of this synthesis, sites of HC storage, and the transport pathway(s) of new HC to the developing epicuticle remain largely unknown (Schal et al, 1998).…”

Identification of α-tocopherol and α-tocopheryl acetate from the cuticle of soybean pods armyworm (Spodoptera cosmioides)

“…GC-MS analysis of the obtained fractions showed the presence of compounds similar to those already described in the literature for lepidopteran larvae, such as alkanes (C n H 2nþ2 ) (n ¼ from 15 to 32) belonging to the iso and anteiso series, alcohols and fatty acids (data not shown) (Guo & Blomquist 1991;Nelson & Blomquist 1995). The difference between the lipidic composition of both exuviae was the presence of vitamin E and its acetate in the S. cosmioides extract.…”

“…The cuticle is the border/boundary between the insects and its environment, protecting them primarily against desiccation and temperature changes (Nelson & Lee 2004). Alkanes, wax esters, free fatty acids among other structures are commonly found in cuticular lipids of Orthoptera, (Soliday et al 1974), Coleoptera (Baker et al 1979) and Lepidoptera (Guo & Blomquist 1991). The chemical and physical characterisation of the insects cuticle are important issues for a better understanding of insects' evolutional aspects, their environmental adaptation and communication cues as well as their resistance to pathogens.…”

Isolation and determination of absolute configurations of insect-produced methyl-branched hydrocarbons

“…It must be noted that, if the stereochemistry of the methyl branch point is controlled by the enoyl-ACP reductase reduction, compounds whose branch points are inserted early in the biosynthesis would have the same spatial orientation as those with branch points inserted after the center of the hydrocarbon chain but would be assigned opposite stereochemical configurations due to nomenclature rules [(R) vs. (S)]. Nevertheless, the available evidence suggests that, at least for monomethyl-branched compounds, the methyl branches are inserted relatively early during chain construction (59)(60)(61)(62).…”