Composição mineral do gafanhoto aposemático semiaquático Tetrataenia surinama (Linnaeus, 1764) (Orthoptera: Acrididae)

Abstract

The aposematic grasshopper Tetrataenia surinama (Linnaeus, 1764) (Orthoptera, Acrididae, Leptysminae) feeds and develops its life cycle associated with the aquatic macrophyte Montrichardia linifera (Arruda) Schott, (Araceae), a plant known as Aninga, considered toxic to vertebrates and widely distributed in the Amazon region, including urban centers. This study aimed to determine, through chemical analysis, the mineral composition of the grasshopper T. surinama and relate it to the mineral composition of its host plant M. linifera (Aninga). The collection of grasshoppers and Aninga was carried out in the area of ​​the Federal Rural University of the Amazon (UFRA), Belém, Pará, from May to July/2017. The collected specimens were transferred to the Insectarium of the State University of Pará (UEPA), where they received an exclusive diet of Aninga leaves for 21 days (NUNES, 1989). The chemical analysis to determine the mineral composition of the grasshopper was performed in the chemical analysis laboratory of the Coordination of Earth Sciences and Ecology (CCTE) of the Museu Paraense Emílio Goeldi (MPEG). The chemical analyses of the grasshopper (in triplicate) followed the protocol of Amarante et al. (2009), which has already been used in the chemical analysis of Aninga. The results obtained for the grasshopper were positive for Calcium (Ca), Magnesium (Mg), Iron (Fe), Copper (Cu), Zinc (Zn), and Manganese (Mn). The element with the highest concentration in T. surinama was Calcium for males (668.44 mg/kg), females (559.18 mg/kg) and immatures (nymphs) (819.85 mg/kg) and the lowest concentration in males was Manganese (44.43 mg/kg) while in females and nymphs it was Copper (43.26 mg/kg and 48.44 mg/kg, respectively). In Aninga, the element with the highest concentration was Manganese (3612.23 mg/kg), which makes it a ‘toxic plant’. Although T. surinama feeds on Aninga (its host plant), it has a low concentration of Manganese and, therefore, cannot be considered toxic if ingested by consumers in the food chain. Therefore, the 'warning colors' (aposematism) existing in the grasshopper does not indicate toxicity, but may represent a survival strategy, a product of the coevolution process of T. surinama with its host plant M. linifera.