Inbred and outbred honey bees ( Apis mellifera ) have similar innate immune responses
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Insectes Sociaux
RESEARCH ARTICLE
Inbred and outbred honey bees (Apis mellifera) have similar innate immune responses G. M. Lee • M. J. F. Brown • B. P. Oldroyd
Received: 20 August 2012 / Revised: 8 November 2012 / Accepted: 15 November 2012 / Published online: 27 November 2012 Ó International Union for the Study of Social Insects (IUSSI) 2012
Abstract Social insect colonies provide ideal conditions for the spread of pathogens. It has been proposed that the extreme polyandry and genetic diversity seen in the colonies of some eusocial insect species is central to a colony’s defence against disease. Indeed, empirically, colonies headed by polyandrous queens have lower incidence of pathogens than genetically uniform monoandrous colonies. The mechanisms of improved resistance in genetically diverse colonies could arise from the genetic diversity among worker genotypes or from increased innate immunity arising from heterozygosity at immune gene loci within individual workers. Here, we investigate the effects of heterozygosity on two components of the honey bee (Apis mellifera) innate immune system: encapsulation and phenoloxidase (PO) activity. No significant effect of heterozygosity on immune system activity was evident for either encapsulation or PO activity. Thus, we conclude that while encapsulation and PO activity are important components of the immune response, it seems that they do not underlie the positive effects of genetic diversity on parasite and pathogen resistance in honey bees. Keywords Apis mellifera Encapsulation Heterozygosity Immunocompetence Inbreeding Phenoloxidase
G. M. Lee B. P. Oldroyd (&) Behaviour and Genetics of Social Insects Laboratory, School of Biological Sciences, University of Sydney, Macleay Building A12, Sydney, NSW 2006, Australia e-mail: [email protected] M. J. F. Brown School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
Introduction Colonies of social insects provide an ideal environment for the spread of parasites and pathogens. Close living conditions, continual physical interaction, high genetic relatedness and overlapping of generations all increase the risk of catastrophic infection from pathogens (Schmid-Hempel, 1998; Wilson-Rich et al., 2009). Social insects have evolved mechanisms that provide effective defence against parasites and pathogens (Schmid-Hempel, 1998; Hughes et al., 2002; Wilson-Rich et al., 2009) including an effective innate immune system and behaviour that reduces disease incidence (Schmid-Hempel, 1998; Strand, 2008; Wilson-Rich et al., 2009). The insect innate immune system consists of humoral defences and cellular defences. Humoral defences include antimicrobial peptides, proteins and enzymatic pathways (Schmid-Hempel, 2005). Cellular defences are those mediated by haemocytes (blood cells) such as phagocytosis and encapsulation (Strand, 2008). Powerful innate immune responses benefit not only individuals, but may also reduce disease transmission among colony members (Evans and Pettis,
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