Phloem-sap feeding by animals: problems and solutions

The incidence of phloem sap feeding by animals appears paradoxical. Although phloem sap is nutrient-rich compared with many other plant products and generally lacking in toxins and feeding deterrents, it is consumed as the dominant or sole diet by a very restricted range of animals, exclusively insects of the order Hemiptera. These insects display two sets of adaptations. First, linked to the high ratio of non-essential:essential amino acids in phloem sap, these insects contain symbiotic micro-organisms which provide them with essential amino acids. For example, bacteria of the genus Buchnera contribute up to 90% of the essential amino acids required by the pea aphid Acyrthosiphon pisum feeding on Vicia faba.…

• BA
  Biotechnology and Biological Sciences Research Council