Rhizoglyphus echinopus (Acari: Acaridae) associated with Atta sexdens (Insecta: Formicidae) Rhizoglyphus echinopus (Acari: Acaridae) associado a Atta sexdens (Insecta: Formicidae)

Arq. Inst. Biol., v.87, 1-4, e0692019, 2020 RESUMO: Quatro deutoninfas de ácaros do bulbo (hipopus) da espécie Rhizoglyphus echinopus (Fumouze & Robin) (Acari: Acaridae) foram encontradas fixadas na cabeça de formigas da espécie Atta sexdens no Rio de Janeiro, Brasil. Essa espécie de ácaro está comumente associada a plantas ornamentais e plantas com bulbos e tubérculos. Os resultados desse estudo fornecem uma visão sobre a relação forética entre ácaros e formigas, indicando o papel destas últimas na dispersão dos primeiros. Apesar da abundância e da fauna diversa do ácaro em formigas, pouco se sabe sobre a diversidade, a biologia, a ecologia e a natureza dessa associação.

A. Silva et al. Among pest insects of Brazilian agriculture and forestry, leafcutting ants are the main agents that cause damage since they attack all cultivated plants (SPIER et al., 2013). The species of the tribe Attini live in symbiosis with basidiomycete fungi, association that is important for the maintenance of the ants colony because it allows them to obtain nutrients and, on the other hand, enables symbiotic fungal growth with the substrates provided by the ants (SILVA et al., 2003). Among the species of the tribe Attini, Atta sexdens, popularly known as leaf cutters, collect fresh vegetation which they use to cultivate a symbiotic fungus inside their nests in order to provide food source to the brood (LUCIA et al., 2014).
Some species of the genus Atta are considered the main agricultural and forest pests in the neotropical region; there is a constant concern with their control in various agroecosystems (LUCIA et al., 2014;DORNELAS et al., 2016).
The association of mites with ants is usually common or mutualist, relying on bacteria, fungi and other resources accumulated within the ant nests. Confirmed parasitic species are rare and largely restricted to the order Mesostigmata (CAMPBELL et al., 2013). The first reference to myrmecophilous mites in Brazil is from SELLNICK (1926).
Mites have radiated into many habitats like phytophagous, mycophagous, saprophagous and parasites, and can be seen in various hosts, as well as in stored products, homes, nests and various types of soils and waste (PHILIPS; DINDAL, 1990).
Species of the family Acaridae are commonly found in humid organic substrates. Rhizoglyphus echinopus (Fumouse & Robin) (Acari: Acaridae) (Robine bulb mite) are typical phoretic mite and widely distributed throughout the world (SILVA et al., 2016). They are known to be good indicators of environmental impact (PAOLETTI et al., 1991) and can accumulate heavy metals in their bodies, making them an important tool as indicators of disturbed sites ( VAN STRAALEN, 1996). This mite can cause injuries on plant tissue creating a gateway to diseases (VENEGAS, 2003;FAN;ZHANG 2004), frequently attacking bulbs, roots, tubers and protected crops (DÍAZ et al., 2000;ZHANG, 2003).
One hundred A. sexdens were collected from fresh leaves of the plants Vernonia condensata Baker (Asteraceae) during October of 2018 in the botanical garden of the Laboratório de Zoologia da Fundação Técnico Educacional Souza Marques (FTESM), located in Cascadura, Rio de Janeiro, Brazil. The ants were properly identified by dichotomic keys from MAYHÉ-NUNES (1991) and GONÇALVES (1961) and checked out for the presence of phoretic mites.
Leaf-cutting ants are a keystone species because of their influence on environmental diversity, productivity, nutrients and energy flow. This species of ants directly and indirectly changes the physical state of biotic and abiotic materials and may cause economic losses (LUCIA et al., 2014).
Mites are the most abundant organisms found in ants nests (CAMPBELL et al., 2013). Four deutonymphs of R. echinopus associated with A. sexdens were found attached to their heads and, according to SILVA et al. (2016), the presence of mites in the head, mouthparts and abdomen of insects make difficult normal feeding behavior. The abundance of mites can also harm the sexual behavior of the phoront (RODRIGUES et al., 2013).
Despite the vast number of mite species that have been described from the association with insects, the study of social insect-mite interactions is still insipient. The mite species that occur in nests of most tropical ants remain totally unknown.