TY - JOUR

T1 - The effects of age and social interactions on innate immunity in a leaf-cutting ant

AU - Armitage, S.A.O.

AU - Boomsma, J.J.

PY - 2010

Y1 - 2010

N2 - Both developmental and environmental factors shape investment in costly immune defences. Social insect workers have different selection pressures on their innate immune system compared to non-social insects because workers do not reproduce and their longevity affects the fitness of relatives. Furthermore, hygienic behavioural defences found in social insects can result in increased survival after fungal infection, although it is not known if there is modulation in physiological immune defence associated with group living vs. solitary living.Here we investigated whether physiological immune defence is affected by both age and the short-term presence or absence of nestmates in the leaf-cutting ant Acromyrmex octospinosus. We predicted that older ants would show immune senescence and that group living may result in prophylactic differences in immune defence compared to solitarily kept ants. We kept old and young workers alone or in nestmate groups for 48 h and assayed a key innate immune system enzyme, expressing phenoloxidase (PO) and its stored precursor (proPO), a defence that acts immediately, i.e. it is constitutive. Short-term solitary living did not affect PO or proPO levels relative to group living controls and we found no evidence for immunosenescence in proPO. However, we found a significant increase in active PO in older workers, which is consistent with two non-mutually exclusive explanations: it could be an adaptive response or indicative of immunosenescence. Our results suggest that future studies of immunosenescence should consider both active immune effectors in the body, such as PO, and the stored potential to express immune defences, such as proPO.

AB - Both developmental and environmental factors shape investment in costly immune defences. Social insect workers have different selection pressures on their innate immune system compared to non-social insects because workers do not reproduce and their longevity affects the fitness of relatives. Furthermore, hygienic behavioural defences found in social insects can result in increased survival after fungal infection, although it is not known if there is modulation in physiological immune defence associated with group living vs. solitary living.Here we investigated whether physiological immune defence is affected by both age and the short-term presence or absence of nestmates in the leaf-cutting ant Acromyrmex octospinosus. We predicted that older ants would show immune senescence and that group living may result in prophylactic differences in immune defence compared to solitarily kept ants. We kept old and young workers alone or in nestmate groups for 48 h and assayed a key innate immune system enzyme, expressing phenoloxidase (PO) and its stored precursor (proPO), a defence that acts immediately, i.e. it is constitutive. Short-term solitary living did not affect PO or proPO levels relative to group living controls and we found no evidence for immunosenescence in proPO. However, we found a significant increase in active PO in older workers, which is consistent with two non-mutually exclusive explanations: it could be an adaptive response or indicative of immunosenescence. Our results suggest that future studies of immunosenescence should consider both active immune effectors in the body, such as PO, and the stored potential to express immune defences, such as proPO.

KW - Acromyrmex octospinosus

KW - Cuticular colour

KW - Immunosenescence

KW - Phenoloxidase

KW - Prophenoloxidase

KW - PROPHENOLOXIDASE-ACTIVATING SYSTEM

KW - DROSOPHILA-MELANOGASTER

KW - DISEASE RESISTANCE

KW - TENEBRIO-MOLITOR

KW - PHENOLOXIDASE ACTIVITY

KW - MUTUALISTIC BACTERIUM

KW - INVERTEBRATE IMMUNITY

KW - EVOLUTIONARY ECOLOGY

KW - MEALWORM BEETLE

KW - INSECT COLONIES

U2 - 10.1016/j.jinsphys.2010.01.009

DO - 10.1016/j.jinsphys.2010.01.009

M3 - Journal article

C2 - 20138051

VL - 56

SP - 780

EP - 787

JO - Journal of Insect Physiology

JF - Journal of Insect Physiology

SN - 0022-1910

IS - 7

ER -