An Essential Nutrient for the Mosquito Culex pipiens1 Associated with Certain Animal-Derived Phospholipids2

Abstract

New hatched larvae of Culex pipiens L. (Diptera: Culicidae) develop to the adult state in a sterile synthetic dietary medium with cholesterol as the only lipid nutrient, but emergent adults are weak and nearly all become trapped at the medium surface. Supplementation of basal medium with 30–60 mg/100 ml of human or bovine plasma beta-lipoprotein Cohn fraction III-0, or 2–4 mg/100 ml of various phospholipids, favors the production of strong adults, many of which are able to fly and survive thereafter for long periods. Of several phospholipids tested, crude animal and egg lecithins, and purified phosphatidylcholine and phosphatidylethanolamine (ex-ovolecithin and ex-bovine brain cephalin, respectively) contain flight activity factor. Purified sphingomyelin (ex-bovine brain), crude vegetable lecithin, refined soy lecithin, synthetic L or DL-dipalmitoyl lecithin and synthetic DL-dipalmitoyl cephalin had no flight factor. All phospholipids and lipoproteins tested slightly increased the rate of development to pupation. In excess of 4 mg/100 ml, all phospholipids were detrimental to larval development. These findings indicate that another lipid nutrient is required in addition to cholesterol, possibly a vertebrate fat-soluble growth factor occurring as a contaminant in various lipid preparations of animal origin, but more probably a sub-molecular component of certain animal phospholipids.