Utilization of Δ5,7 ‐ and Δ8‐sterols by larvae of Heliothis zea

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Abstract
Larvae from two populations of Heliothis zea were reared on artificial diets containing various sterols, which supported suboptimal growth, and their tissue sterols were characterized in order to determine how these dietary sterols are utilized by this insect. The sterols studied included Δ5,7‐sterols (7‐dehydrocholesterol or ergosterol), Δ8‐sterols (lanosterol and/or 24‐dihydrolanosterol), and a Δ5‐sterol (4,4‐dimethylcholesterol). Although larvae did not develop on 4,4‐dimethylcholesterol, those fed primarily Δ8‐4,4,14‐trimethylsterols developed to the third instar. When the latter sterols were spared with cholesterol, the larvae reached the sixth instar and contained 4,4,14‐trimethylsterols as well as cholesterol in their tissues. When larvae were fed 7‐dehydrocholesterol, H. zea can dealkylate and saturate the side chain of the Δ5,7,22‐24β‐methylsterol, it carries out little metabolism of the B ring of the nucleus. These studies demonstrate that, when Δ5,7‐ or Δ8‐sterols are the principal sterols in the diet of H. zea, they are absorbed and incorporated into its tissues, although they slow the rate of growth and may prevent complete development of the larva.