PARENT SESSION
Tuesday, August 8, 8:00-11:30 am
COS 30 - Invertebrate ecology
L-5, L-6, L-7, Lobby Level, Cook Convention Center
Presiders: C Johnson

Cellular vs. humoral immunity in the Caribbean termite Nasutitermes acajutlae: the role of environmental conditions on immunocompetence.

Fuller, Claire^*,1, Postava-Davignon, Marielle², Rosengaus, Rebeca², ¹ Murray State University, Murray, KY² Northeastern University, Boston, MA

ABSTRACT- The impact that pathogens and parasites have on different aspects of the biology of solitary hosts, including the evolution of different life history attributes and trade-offs has received a great deal of attention in the past 15 years. However, little is known about the interaction between the environmental conditions surrounding eusocial hosts and their immune responses. We examined how a number of abiotic parameters (ambient and internal nest temperature, ambient and internal nest relative humidity, soil temperature, soil pH, light) and nest volume are related to two aspects of termite immunity: a) the phenoloxidase enzymatic cascade (PO activity) and b) total hemolymph protein levels in field-caught workers of the Caribbean termite Nasutitermes acajutlae. Both of these immune parameters have been implicated in the resistance to pathogens in solitary insects. Principle Components Analysis (PCA) indicates that environmental components external to the nest (ambient temperature, ambient RH, soil temperature and light) comprise the majority (PC1 = 68.2%) of variation in the abiotic components measured. Internal variables (nest temperature and RH) and nest volume account for 37.5% (PC 2) of the variation with pH comprising the remainder (PC3). Results of our regression analyses also show that PO activity was positively related to ambient temperature and nest volume and that, in contrast to PO activity, the concentration of total hemolymph proteins decreased with increasing ambient temperature and internal nest relative humidity. Given that immunity is costly in insects, the increase of specific immune-related protein (such as phenoloxidase) at the expense of total hemolymph protein levels could represent a trade-off between the cellular and humoral components of the immune responses in termites. Further studies exploring the relationship between the abiotic environment, termite immunity and susceptibility, and ultimately, termite colony fitness are currently underway.

Key words: ecological immunity, abiotic environment, termite