Micro-PIXE studies of elemental distribution in sap-feeding insects associated with Ni hyperaccumulator, Berkheya coddii

Abstract

The aim of this study was to determine elemental composition of sap-feeding insects inhabiting various parts of the Ni hyperaccumulating plant Berkheya coddii Roessl., the endemic species of ultramafic outcrops in Mpumalanga, South Africa. Three species were examined: the aphid Protaphis pseudocardui (Aphididae), abundant on young leaves; the mealybug Orthesia sp. (Ortheziidae) colonizing underground parts of this plant, and the bug Norialsus berkheyae (Cixiidae) living on young shoots. Maps of Ni, K, Ca, Zn, and Fe for selected body areas of these species were generated using Dynamic Analysis method on the basis of particle-induced X-ray emission (micro-PIXE) and proton backscattering (BS) measurements. Atomic absorption spectrometry was used to determine Ni, Zn, Cu, Fe contents in the B. coddii organs, in some sapfeeding insect species including these mentioned above, and in the assassin bug hunting on Chrysolina pardalina, a monophagous beetle of B. coddii. Bioaccumulation factor for Ni in the examined species was below 0.05, and much higher for other metals (Zn ‡ 2; Fe £ 5). Ni distribution within body was species-dependent. It was the highest in the antennae of P. pseudocardui, in the head of Orthesia sp. and in the metathorax of N. berkheyae. Distribution patterns of other metals were different among examined species. Ca was recorded mainly in peripheral parts of the body in all species. Zn showed similar distribution to Ni. Fe distribution was similar to Ni only in the mealybugs. Uneven concentrations of metals within selected body regions indicated their relations with specific organs. Analysis of Ni transfer to higher trophic levels was done on the basis of two food nets: B. coddii-C. pardalina-Rhinocoris neavii and B. coddii-P. pseudocardui-Polyrhachis ant and led to the conclusion that the role of sap-feeding insects in Ni transfer was marginal.

Ultrastructure and regeneration of midgut epithelial cells in Lithobius forficatus (Chilopoda, Lithobiidae)

“…The digestive system of myriapods and other terrestrial arthropods, especially the midgut epithelium, is a first line of defense against toxic substances, playing a role in the elimination of pathogens and harmful materials that originate in food (Hopkin ; Loeb & Hakim ; Migula et al. ; Rost‐Roszkowska et al. ; Hakim et al.…”

“…The digestive system of myriapods and other terrestrial arthropods, especially the midgut epithelium, is a first line of defense against toxic substances, playing a role in the elimination of pathogens and harmful materials that originate in food (Hopkin 1989;Loeb & Hakim 1996;Migula et al 2007;Rost-Roszkowska et al 2008;Hakim et al 2010). In myriapods, toxic metals are accumulated in the midgut epithelial cells, where they are neutralized in crystalline structures called spherites.…”

High‐nickel insects and nickel hyperaccumulator plants: A review

“…For example, Migula et al (2007) suggested that how collected specimens are handled after capture could affect whole-body Ni measurements. Insects killed immediately upon capture would retain their gut contents, whereas those captured but not immediately killed would have the opportunity to at least partially empty their digestive tracts.…”

“…Note that, as mentioned previously, an insect species may meet the criterion described above for samples of larvae or nymphs but not for samples of adults (or vice versa), from the same insect species. This is illustrated by Anoplocnemis dallasiana Lethierry & Serville (Heteroptera: Coreidae) in Table 1: Migula et al (2007) reported 1 300 +g Ni/g in nymphs but only 280 +g Ni/g in adults. In the reverse situation, they reported less from nymphs (43 +g Ni/g) but more from adults (520 +g Ni/g) of Rhinocoris neavei Bergroth (Heteroptera: Reduviidae).…”

“…That such experimental confirmation is necessary stems from studies (e.g., Boyd, 2007a;Sorenson et al, 2009) in which relatively high levels of metal tolerance are reported from insects that are unlikely to be exposed to high metal levels in their natural environments. Thus it seems unwise to assume Ni tolerance is greater in high-Ni insects, especially since there are herbivores of Ni hyperaccumulator plants that do not have high whole-body Ni concentrations yet also feed upon high-Ni plant tissues (Wall & Boyd, 2002;Boyd et al, 2006a, b;Migula et al, 2007).…”