Disease resistance in the drywood termite, Incisitermes schwarzi: Does nesting ecology affect immunocompetence?

Daniel V. Calleri II1a*, Rebeca B. Rosengaus2b, and James F.A. Traniello1c

1Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215-2406, USA
2Department of Biology, Northeastern University, 134 Mugar Life Science Building, 360 Huntington Avenue, Boston, MA 02115-5000

Abstract

Termites live in nests that can differ in microbial load and thus vary in degree of disease risk. It was hypothesized that termite investment in immune response would differ in species living in nest environments that vary in the richness and abundance of microbes. Using the drywood termite, Incisitermes schwarzi Banks (Isoptera: Kalotermitidae), as a model for species having low nest and cuticular microbial loads, the susceptibility of individuals and groups to conidia of the entomopathogenic fungus, Metarhizium anisopliae Sorokin (Hypocreales: Clavicipitaceae), was examined. The survivorship of I. schwarzi was compared to that of the dampwood termite, Zootermopsis angusticollis Hagen (Termopsidae), a species with comparatively high microbial loads. The results indicated that I. schwarzi derives similar benefits from group living as Z. angusticollis: isolated termites had 5.5 times the hazard ratio of death relative to termites nesting in groups of 25 while termites in groups of 10 did not differ significantly from the groups of 25. The results also indicated, after controlling for the influence of group size and conidia exposure on survivorship, that Z. angusticollis was significantly more susceptible to fungal infection than I. schwarzi, the former having 1.6 times the hazard ratio of death relative to drywood termites. Thus, disease susceptibility and individual investment in immunocompetence may not be dependent on interspecific variation in microbial pressures. The data validate prior studies indicating that sociality has benefits in infection control and suggest that social mechanisms of disease resistance, rather than individual physiological and immunological adaptations, may have been the principle target of selection related to variation in infection risk from microbes in the nest environment of different termite species.

Keywords: ecological immunology, entomopathogenic fungus, herd immunity, infection control, microbial load

Correspondence: a* dcalleri@gmail.com, b r.rosengaus@neu.edu, c jft@bu.edu *Corresponding author
Associate Editor: Robert Jeanne was editor of this paper

Received: 25 March 2008 | Accepted: 9 January 2009 | Published: 8 May 2010

ISSN: 1536-2442 | Volume 10, Number 44

Calleri II DV, Rosengaus RB, Traniello JFA. 2010. Disease resistance in the drywood termite, Incisitermes schwarzi: Does nesting ecology affect immunocompetence? 12pp. Journal of Insect Science 10:44, available online: insectscience.org/10.44


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