Binocular processes in vernier acuity

The contribution of synthesis and dietary sequestration to the high arachidonate content of the lone star tick, Amblyomma americanum, salivary glands was investigated by assessing the salivary metabolites of various radiolabeled fatty acid substrates administered to partially fed females. A portion of each of the fatty acids studied was incorporated into the fatty acid moiety of the phospholipid fraction. 14C]acetate was metabolized only into myristic, palmitic, palmitoleic, steric, and oleic acids. 3H]oleic acid, 14C]linoleic acid, 14C]gamma-linolenic acid and 14C]eicosatrienoic acids were incorporated into salivary gland phospholipids but underwent little change including elongation and/or desaturation to arachidonate. Ingested 3H]arachidonic acid was readily taken up by the salivary gland and distributed among the lipid classes in a pattern markedly different from that of the other fatty acids tested. We conclude that ticks are unable to synthesize arachidonic acid for incorporation into the salivary glands, but rather sequester it from the host bloodmeal.