A new approach to mark termites (Cornitermes cumulans (Kollar) Blattodea: Isoptera) for laboratory bioassays.

P F Cristaldo,L R Paiva,O Miramontes,A Marins,O Desouza

doi:10.1590/1519-6984.03316

Abstract

Behavioral lab bioassays involving termites must be promptly performed to allow intended observations prior to death from dissecation, typical of these soft-bodied insects. To this end, topic markers have been proposed as an alternative to histological stains which, while not always toxic are inevitably lengthy to apply. Among recommended topic markers, gouache is easy to apply, dries out quickly, but it is known affect termites in the long run, being suitable only to short-term bioassays. Its alternative, colored glue, is also easy to apply, but it takes long to dry and it is too dense and heavy, being thus prone to affect termite walking patterns. Here we tested a mix of gouache and colored glue aiming to combine the qualities of both into a suitable topical marker for Cornitermes cumulans termites. Similar patterns of survival presented by marked and unmarked termites ruled out concerns about toxicity of this mixture. Such results were consistent across distinct group densities evidencing that the mixture does not interfere with, nor it is affected by, crowding effects. Because crowding regulates interindividual interactions and these underlie most behaviors, the mixture can be thought to be suitable to behavioral studies. We argue that this 1:2 glue:gouache mixture is an excellent alternative to mark termites for lab bioassays. Being atoxic, cheap, easy to apply, and non-invasive, this mixture may happen to be useful not only for termites but also in bioassaying other similarly soft-bodied insects.

Highlights

Despite the well-known termite importance as pest (Su, 2002) and their key role in nutrient cycle (Alho, 2008; DeSouza et al, 2009; Pringle et al, 2010), basic aspects of termite biology and ecology remain open to investigation
In order to verify the suitability of the use of gouache and colored glue mixture as a topic marker on termites, survival bioassays were performed using workers collected from field colonies of C. cumulans (N= 3), in Viçosa, state of Minas Gerais, in southeastern Brazil
An ideal topic marker for insects should be durable, non-toxic, light, easy and quick to apply (Walker and Wineriter, 1981; Hagler and Jackson, 2001). All these aspects could be observed in the mixture of gouache and colored glue tested here, proving it to be a good alternative as a marker for termites in laboratory bioassays

Summary

Introduction

Despite the well-known termite importance as pest (Su, 2002) and their key role in nutrient cycle (Alho, 2008; DeSouza et al, 2009; Pringle et al, 2010), basic aspects of termite biology and ecology remain open to investigation. Bioassays have been used as a powerful tool in the study of behavioral ecology, whereby it is possible to obtain responses of model organisms against different intrinsic and/or extrinsic stimuli (Hoskins and Craig, 1962). They can provide relevant information about mechanisms involved in the walking pattern of organisms during foraging Nobre et al, 2007), sexual partners, nesting site and/or estimation of population (e.g. Su et al, 1991; Evans et al 1998) Many of such assays rely on markers to identify the individual observed, allowing a better control of experiments and accurate observations (Hagler and Jackson, 2001)

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