Effects of diet and metamorphosis upon the sterol composition of the butterfly Morpho peleides

Abstract

Whole body sterol metabolism in insects has seldom been studied. We were able to design an appropriate study at a butterfly farm in Belize. We collected six larvas of butterfly (Morpho peleides), their food (leaves of Pterocarpus bayessii), and their excretions. In addition, six adult butterflies were collected. The sterols of the diet, the larva, and adult butterfly were analyzed by gas-liquid chromatography. The structures of these sterols were identified by digitonin precipitation, GC-MS, and NMR. Four sterols (cholesterol, campesterol, stigmasterol, and sitosterol) and a sterol mixture were found in the food, the body, and the excreta of the larva. The tissue sterol content of the larva was 326 mg. They consumed 276 mg of sterols per day. Their excretion was 185 mg per day as sterols. The total tissue sterol contents of the larva and butterfly were similar, but they had different sterol compositions, which indicated interconversion of sterols during development. There was a progressive increase in the cholesterol content from larva to butterfly and a decrease in the content of sitosterol and other plant sterols, which were likely converted to cholesterol. Our data indicated an active sterol metabolism in butterfly larva. Diet played an important role in determining its sterol composition. During metamorphosis, there was an interconversion of sterols. This is the first paper documenting the fecal sterol excretion in insects as related to dietary intakes. Insects and vertebrates share many common metabolic pathways. In many areas of research, insects are useful models that can facilitate our general understanding of biology (1). However, unlike vertebrates, insects are unable to biosynthesize sterols and must acquire these essential nutrients from the diet (2-5). In addition to a role as a structural component of the cell membranes, cholesterol serves as the precursor of the insect molting hormone ecdysteroids (6, 7). Different aspects of sterol metabolism in insects have been studied in many species (8). Excellent reviews are available on this subject (4, 9).The butterfly of the Lepidoptera order undergoes metamorphosis from larva to butterfly. The larva feed on the leaves of plants and then spin a chrysalis. The butterfly feeds on flower nectar, which is available later in the year. We found no information in the literature about the sterol composition of the butterfly before and after metamorphosis and no information about how the diet of the larva might influence its sterol composition. In a recently published study, we found that the butterfly drastically decreases its body weight and body fat during metamorphosis (10).On a trip to Belize, Central America, we visited the Butterfly Farm at Chaa Creek. Chaa Creek is a tourist attraction and hostel for travelers in Belize. As we have developed an interest in the evolutionary patterns of fatty acids, having previously studied snails and slugs (11), we saw the potentialities of butterfly research and discussed our ideas with the scientific director (M...

Metabolic Allometry during Development and Metamorphosis of the SilkwormBombyx mori: Analyses, Patterns, and Mechanisms

“…Overall, the lipid contents we report for B. mori are in the general range reported for a number of species of Lepidoptera (Domroese and Gilbert 1964;Fast 1964;Prasad et al 1986). Lipid and sterol concentrations are highly dependent on diet content and nutritional levels, even within species (Satake et al 2000;Connor et al 2006), so reported differences in the literature could be related, in part, to animal husbandry as well as to fundamental interor intraspecific differences. Lipid content differences in the cecropia moth are gender dependent (Domroese and Gilbert 1964), with females having higher lipid contents than males.…”

Nutritional value of insects and ways to manipulate their composition

“…Total sterol content and the variation seems a function of species, diet, life stage and season (Connor et al, 2006;Koštál et al, 2013;Liland et al, 2017). While insects contain a variety of sterols often β-sitosterol, cholesterol, or 7-dehydrocholesterol are the most abundant (Cerda et al, 2001;Cheseto et al 2015;Connor et al, 2006;Jing and Behmer, 2020;Koštál et al, 2013;Liland et al, 2017;Mlček et al, 2019;Sabolová et al, 2016;Svoboda et al, 1995). High dietary levels of sterols, such as cholesterol, can increase the risk of atherosclerosis in humans and some species of monkeys (Hopkins, 1992;Rudel et al, 1998).…”

Energetic loads and informational entropy during insect metamorphosis: Measuring structural variability and self-organization

“…The significant effect of larval diet on the concentration of pupal energetic loads (especially on lipid content) has been suggested (Nestel et al, 2004;Nishiura et al, 2006;Connor et al, 2006). On the other hand, in some cases larval diet composition does seem to affect neither carbohydrates nor protein levels (Slansky, 1985;Zanotto et al, 1993).…”