Pearl bodies

Pearl bodies are small (0.5 - 3.0 mm), lustrous, pearl-like food bodies produced from the epidermis of leaves, petioles and shoots of certain plants. They are rich in lipids, proteins and carbohydrates, and are sought after by various arthropods and ants, that carry out vigorous protection of the plant against herbivores, thus functioning as a biotic defence. They are globose or club-shaped on short peduncles, easily detached from the plant, and are food sources in the same sense as Beltian bodies, Müllerian bodies, Beccarian bodies, Coccid secretions and nectaries. They occur in at least 19 plant families (1982) with tropical and subtropical distribution.

Cells or tissues that offer food rewards to arthropods are commonplace in the plant world and are an important way of establishing symbiotic relationships. Ants collect these energy-rich bodies (27.8 kJ/g dry weight) and carry them into their nests. Removal of these bodies appears to stimulate the formation of new ones in the same place. The simultaneous presence of pearl bodies, ant domatia and extrafloral nectaries, suggest a facultative plant-ant mutualism. Early researchers dubbed these bodies 'perldrüsen' (Meyen 1837), 'pärlharen' (Nils Holmgren 1911) and 'perlules' (Kazimierz Stefan Rouppert 1926). Pearl bodies appear to be the primary, and possibly the only nutrient for ants inhabiting Central American myrmecophytes.

Phytophagous mites such as Tetranychus kanzawai have been observed feeding on pearl bodies produced by Cayratia japonica of the Vitaceae family, a family in which pearl bodies are common. It also appears possible that the predatory mite Euseius sojaensis uses the pearl bodies as an alternative food source.

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