Imidacloprid-Induced Impairment of Mushroom Bodies and Behavior of the Native Stingless Bee Melipona quadrifasciata anthidioides

Declines in pollinator colonies represent a worldwide concern. The widespread use of agricultural pesticides is recognized as a potential cause of these declines. Previous studies have examined the effects of neonicotinoid insecticides such as imidacloprid on pollinator colonies, but these investigations have mainly focused on adult honey bees. Native stingless bees (Hymenoptera: Apidae: Meliponinae) are key pollinators in neotropical areas and are threatened with extinction due to deforestation and pesticide use. Few studies have directly investigated the effects of pesticides on these pollinators. Furthermore, the existing impact studies did not address the issue of larval ingestion of contaminated pollen and nectar, which could potentially have dire consequences for the colony. Here, we assessed the effects of imidacloprid ingestion by stingless bee larvae on their survival, development, neuromorphology and adult walking behavior. Increasing doses of imidacloprid were added to the diet provided to individual worker larvae of the stingless bee Melipona quadrifasciata anthidioides throughout their development. Survival rates above 50% were only observed at insecticide doses lower than 0.0056 µg active ingredient (a.i.)/bee. No sublethal effect on body mass or developmental time was observed in the surviving insects, but the pesticide treatment negatively affected the development of mushroom bodies in the brain and impaired the walking behavior of newly emerged adult workers. Therefore, stingless bee larvae are particularly susceptible to imidacloprid, as it caused both high mortality and sublethal effects that impaired brain development and compromised mobility at the young adult stage. These findings demonstrate the lethal effects of imidacloprid on native stingless bees and provide evidence of novel serious sublethal effects that may compromise colony survival. The ecological and economic importance of neotropical stingless bees as pollinators, their susceptibility to insecticides and the vulnerability of their larvae to insecticide exposure emphasize the importance of studying these species

Survival plots of stingless bee workers (<i>Melipona quadrifasciata anthidioides</i>) reared on imidacloprid-contaminated diets containing increasing doses of the insecticide.

<p>The survival curves of workers bees exposed to imidaclorpid doses between 0.28 e 28 µg a.i./bee were not significantly different and were therefore coded with the same color (i.e., blue).</p

Median survival times (TL₅₀) of stingless bee workers (<i>Melipona quadrifasciata anthidioides</i>) reared on imidacloprid-contaminated diets containing increasing doses of the insecticide.

<p>Median survival times (TL₅₀) of stingless bee workers (<i>Melipona quadrifasciata anthidioides</i>) reared on imidacloprid-contaminated diets containing increasing doses of the insecticide.</p

Effect of larva ingestion of imidaclorprid-contaminated diet on the distance walked (A), walking velocity (B), resting time (C) and number of stops in the arena (D) of individual adult workers (at different ages following emergence) of the stingless bee <i>Melipona quadrifasciata anthidioides</i>.

<p>The symbols represent means and standard error.</p

Serial histological sections of the brain of a stingless bee worker (<i>Melipona quadrifasciata anthidioides</i>).

<p> The edges of the mushroom bodies are delineated with white lines. The sections are ordered such that A, D and H represent the beginning, middle and end of the structure, respectively. MC, median calyx; LC, lateral calyx; VL, vertical lobe; MB, mushroom bodies; Oce, oceli; Ant, antennal lobe; OL, optic lobe; CB, central body. Bar: 500 µm.</p

Abelhas Euglossini (Apidae) de áreas de Mata Atlântica: abundância, riqueza e aspectos biológicos Euglossine bees (Apidae) from Atlantic Forest sites: abundance, richness, and biological aspects

<abstract language="eng">Collection data of Euglossinae males from Parque Estadual do Rio Doce (PERD) and Viçosa, both areas with remnants of Atlantic Rain Forest (Mata Atlântica) in Minas Gerais state, Brazil are presented. Comparisons made among three fragments with different sizes and states of disturbance from Viçosa showed differences in abundance of most common species and apparently, Eulaema nigrita Lepeletir, 1841 can be an useful indicator of disturbed sites. Some populations of euglossine bees seems to be restrict to a forest fragment, there being few or no flow of individuals or species of one fragment to another, even when they are only 1 km apart. 15 species of euglossines were sampled in PERD, and the most abundant was Eulaema cingulata (Fabricius, 1804). At Viçosa, 10 species were sampled, E. nigrita was the predominant one. Methyl salicylate attracted no males at both sites, in spite of large numbers of species and individuals sampled using this bait in other regions. The majority of species and individuals were collected in the rainy season. Only 0,58% of sampled males carried orchid pollinia (Catasetum Richard, Cycnoches Lindley and Coryanthes Hook) on their bodies. Emergence data of four species of Euglossa Latreille, 1802 reared from trap nests suggest that sex ratio in Euglossini is not a constant within the tribe. A list of 57 euglossine species now known to occur in Mata Atlântica are offered