Original article Ants as bioaccumulators of metals from soils: Body content and tissue-specific distribution of metals in the ant Crematogaster scutellaris Elisa Gramigni a , Silvia Calusi b , Nicla Gelli b , Lorenzo Giuntini b , Mirko Massi b , Giovanni Delfino a , Guido Chelazzi a, c , David Baracchi a , Filippo Frizzi a , Giacomo Santini a, c, * a Department of Biology, University of Florence, Via Madonna del Piano 6, 50019 Sesto Fiorentino, Italy b Department of Physics and Astronomy, University of Florence, INFN Sezione di Firenze, Via Sansone 1, 50019 Sesto Fiorentino, Florence, Italy c CESPRO, University of Florence, Via Galcianese 20H, 59100 Prato, Italy article info Article history: Received 7 March 2013 Received in revised form 24 May 2013 Accepted 27 May 2013 Available online 7 June 2013 Handling editor: Stefan Schrader Keywords: Ants Metals Crematogaster scutellaris Micro-PIXE abstract Ants possess several features that make them good candidates as indicators of environmental contam- ination. Concentrations of six metals (Cu, Cd, Ni, Mn, Pb and Zn) were investigated in Crematogaster scutellaris, a myrmicine ant common throughout the Mediterranean basin. Concentrations of metals in ant bodies and soil samples from polluted and unpolluted sites were compared. Tissue-specific distri- bution of metals in a non-soluble form was examined using a novel technique that coupled histological imagery and micro-PIXE analysis. Zinc and cadmium accumulated in ants with respect to the soil. Copper body burdens were independent of soil concentration, while lower concentrations of nickel, manganese and lead were found in ants than in the soil, although ant body content was correlated with soil con- centrations. Most of the metals were concentrated in the midgut, the Malpighian tubules and fat body, supporting the role of these organs as primary sites of metal storage and contaminant immobilization. Ó 2013 Elsevier Masson SAS. All rights reserved. 1. Introduction Metals represent one of the major classes of contaminants in both terrestrial and aquatic environments [1e3]. The deleterious effects of some metals are well known, and have been described at all levels of biological organization, ranging from cells to ecosys- tems [4,5]. Several kinds of organisms have been used to study the impact of metal pollution in terrestrial ecosystems [6,7]. Among these, ants possess several features that make them good candi- dates as indicators of environmental contamination [8e11]. Their worldwide distribution and abundance, ease of collection and identification all play a crucial role [12e14]. Furthermore, ants have a key role in ecosystem functioning and occupy all trophic positions from herbivores to predators, with a predominance of omnivores [15,16], and therefore potentially act as efficient collectors of pollutants within ecosystems [17]. In addition, ant colonies can be seen as a type of perennial “superorganism”, whose life expectancy (>10 years in some cases) generally exceeds the life span of the majority of other invertebrates [18], making long-term effects of pollutants more easily detectable. Despite these features, reports on the use of ants in studying the impact of metals are rare when compared to other arthropods (see Ref. [9] for a review). Selective accumulation of specific metals within the ant body occurs in several ant species [9e11,19e22]. Evidence has shown that metal pollution may affect ant behaviour [23] and impair im- mune responses [24]. Finally, effects on population structure and community composition along metal pollution gradients have also been reported [25e27]. The available literature reveals both taxonomic and geograph- ical biases. The majority of studies, in fact, predominantly consid- ered Formicine ants (and among these Formica, Lasius and Camponotus spp.), mainly from north and central Europe. Comparatively less is known for Myrmicinae or other subfamilies and, to the best of our knowledge, no report exists on species from southern latitudes. Since different species show different accu- mulation patterns [9,20,28], obtaining more information on metal * Corresponding author. Department of Biology, University of Florence, Via Ma- donna del Piano 6, 50019 Sesto Fiorentino, Italy. Tel.: þ39 055 457 4721; fax: þ39 055 4574906. E-mail address: giacomo.santini@unifi.it (G. Santini). Contents lists available at SciVerse ScienceDirect European Journal of Soil Biology journal homepage: http://www.elsevier.com/locate/ejsobi 1164-5563/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved. http://dx.doi.org/10.1016/j.ejsobi.2013.05.006 European Journal of Soil Biology 58 (2013) 24e31