Article

Disease resistance: A benefit of sociality in the dampwood termite Zootermopsis angusticollis (Isoptera: Termopsidae)

Department of Biology, Boston University, Boston, Massachusetts, United States
Behavioral Ecology and Sociobiology (Impact Factor: 3.05). 01/1998; 44(2):125-134. DOI: 10.1007/s002650050523

ABSTRACT The benefit of sociality in relation to disease susceptibility was studied in the dampwood termite Zootermopsis angusticollis. Although contact with high concentrations of fungal conidia is lethal, the survivorship of nymphs exposed to spore suspensions
ranging from 6 × 106 to 2 × 108 spores/ml of the fungus Metarhizium anisopliae increased with group size. The survivorship (measured as LT50) of isolated individuals ranged from 3.0 to 4.8 days, but infected nymphs living in groups of 10 and 25 individuals survived
significantly longer (5.6–8.3 and 5.6–9.1 days, respectively). In most cases, there were no significant differences in the
survival distributions of the 10- and 25-termite groups. When nymphs were infected with concentrations of 7 × 101–7 × 104 spores/ml and allowed to interact with healthy nestmates, fungal infections were not contracted by the unexposed termites.
Moreover, infected termites benefitted from social contact with unexposed nestmates: their survival rates were significantly
higher than those of infected termites living with similarly infected nestmates. Allogrooming, which increased in frequency
during and after exposure to conidia, appeared to remove potentially infectious spores from the cuticle, thus increasing termite
survivorship. These results suggest that allogrooming plays a crucial role in the control of disease and its death hazard
in termites. The infection-reducing advantage of group living may have been significant in the evolution of social behavior
in the Isoptera.

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    • "Behavioural mechanisms include the use of vibratory displays to warn nestmates about the presence of lethal fungal concentrations to which they respond by absconding (Rosengaus et al., 1999b; Myles, 2002), or increasing rates of mutual grooming when exposed to pathogens (Rosengaus et al., 1998, 2000), and walling off of infected areas of a colony (Milner et al., 1998; Staples and Milner, 2000). Physiological mechanisms include fungistatic secretions associated with exocrine glands and faecal pellets of some termites that reduce microbial growth within nest chambers (Rosengaus et al., 1998, 2004), enhancement of resistance to infection through cellular and humoral immune responses (Rosengaus et al., 1999a; Traniello et al., 2002), and salivary gland secretions containing antibiotic peptides (Lamberty et al., 2001). These defensive mechanisms demand cooperation between members of social groups or altruistic behaviours of some colony members for the benefit of the whole colony, which result in avoidance, control or elimination of parasitic infections (Mü ller and Schmid-Hempel, 1993; Cremer et al., 2007). "
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