video: Soldier nymphs of Nipponaphis monzeni repairing the gall. view more
Credit: Movie courtesy of Mayako Kutsukake.
Some species of aphids use suicide bombing as a form of social defense to protect colonies from predators, according to a study. The tendency of social insects, such as ants, termites, and aphids, to engage in self-sacrificing acts of altruism for the benefit of colonies has long been considered one of nature's oddities. Mayako Kutsukake, Takema Fukatsu, and colleagues describe the biochemical underpinnings of a form of self-destructive defense mounted by the social aphid Nipponaphis monzeni when predators attack the aphid's colonies, which are housed in galls on winter hazel trees. In the spring, when lepidopteran insects dig into the galls in search of food, dozens of aphid soldiers scurry toward the wound and expel lipid-rich body fluids. In a risky operation that can shut them out of the gall or smother them outright, the rapidly shriveling soldiers briskly plaster the wound with the milky body fluids, which coagulate and close the wound. Biochemical analysis of the fluid revealed a potent clot-forming mix: an abundance of previously undescribed, large, globular, lipid-laden cells that resemble hemocytes; the amino acid tyrosine; the enzyme phenoloxidase, which converts tyrosine to melanin in a stepwise pathway; and a repeat-containing protein, which is woven into the clot's latticework. The synchronized expulsion of lipid-rich fluid by aphid soldiers creates a soft clot around the gall wound that is swiftly hardened and melanin-darkened through the action of phenoloxidase. While such wound healing in individual N. monzeni represents an unremarkable form of innate immunity triggered by predators, the soldiers' collective action is an amplified immune response marshaled for social defense. According to the authors, the study uncovers molecular clues to the evolutionary roots of altruistic social defense.
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Article #19-00917: "Exaggeration and cooption of innate immunity for social defense," by Mayako Kutsukake et al.
MEDIA CONTACT: Takema Fukatsu, National Institute of Advanced industrial Science and Technology, Tsukuba, JAPAN; tel: 81-29-861-6087, 81-90-1422-6897; e-mail: <t-fukatsu@aist.go.jp>; Mayako Kutsukake, National Institute of Advanced industrial Science and Technology, Tsukuba, JAPAN; e-mail: <m-kutsukake@aist.go.jp>
Journal
Proceedings of the National Academy of Sciences