Research in Biochemistry - Lipid metabolism

Chill out! Wiggling larvae are difficult to handle. Before working with larvae, they're chilled in a bucket of crushed ice to slow them down.

Lipids are a group of chemical compounds that include fats, oils, and similar substances that are not soluble in water. A good example is corn oil. Lipids are a necessary and important part of most animals' diets. Along with proteins and carbohydrates, they are a basic building material for cells. Manducas are easy to raise in large numbers, are relatively large as insects go, and are basically little green food processors. That makes them ideal living laboratories for learning how animals metabolize (digest) lipids. When Manducas eat, the food enters the large stomach or mid-gut, where enzymes break down the lipids and transport them through the walls of the mid-gut out into the hemolymph, or blood. The hemolymph carries the metabolized lipids throughout the Manduca's body. Some is used right away as the larva grows, and some is stored in the fat bodies–structures surrounding the mid-gut–to be used during molting and pupation, when the Manduca can't eat. Researchers feed Manduca larvae special lipids containing radioactive tracers that allow them to measure how fast the lipids are digested, and to identify exactly where they go. The mid-guts can even be removed from the larvae and kept alive (and metabolizing) for up to two hours! This research is helping scientists better understand how lipids are processed by animals (including humans). Practical applications are in food and nutrition, disease prevention and treatment, and in insect pest control. (Many insecticides are toxins dissolved in a lipid base. Lillian Canavoso, shown in the photographs, collects hemolymph from about 200 Manducas per day to study the process of lipid matabolism.

Processing Manducas Carefully cutting them open. Extracting hemolymph (blood). Removing the midgut (stomach).

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