Research Article Sub-lethal doses of neonicotinoid and carbamate insecticides reduce the lifespan and alter the expression of immune health and detoxification related genes of honey bees (Apis mellifera)

Abstract

Honey bees (Apis mellifera) are exposed to sublethal doses of insecticides, but little is known about insecticide effects on their survivorship associated to health-related gene expression. To test the effect of sublethal doses of clothianidin, imidacloprid and carbaryl on the lifespan and health of honey bees, workers were orally and topically exposed to LD5 doses of these insecticides. The survivorship of treated bees was monitored and the expression of three immune-related genes, hymenoptaecin (AmHym), basket (AmBask) and lysozyme (AmLyso2) was analyzed at 24 and 72 hours post treatment (hpt), as well as that of the antioxidant-related gene vitellogenin (AmVit2), the poly-U binding factor (AmPuf68), and the detoxification gene cytochrome P450 (AmCYP9Q3). The three insecticides significantly reduced the length of life of bees but the mode of application did not affect survivorship. AmHym, AmBask and AmVit2 expression was significantly down-regulated at 72 hpt in bees treated with clothianidin and imidacloprid, indicating immunosuppression. However, AmLyso2, AmCYP9Q3 and AmPuf68 were significantly up-regulated. The down-regulation of AmVit2 could have caused decreased resistance to oxidative stress. AmPuf68 expression could be associated with increased protection against xenobionts. AmCYP9Q3 was up-regulated at 24 and 72 hpt H Tarek, et al. 2 Genetics and Molecular Research 17 (2): gmr16039908 in oral exposures, but only until 72 hpt in topical exposures, indicating faster sensitivity towards detoxification mechanisms in oral treatments. This study demonstrated detrimental effects of sublethal doses of clothianidin, imidacloprid and carbaryl on honey bee survivorship, immunity and antioxidant mechanisms, and an induction of defense and detoxification responses that could be physiologically costly to the bees.

Antioxidation Defenses of Apis mellifera Queens and Workers Respond to Imidacloprid in Different Age-Dependent Ways: Old Queens Are Resistant, Foragers Are Not

“…Johnson and Carey [ 31 ] and Margotta et al [ 32 ] suggested that, due to the oxidative stress caused by the foraging environment and working flight muscles, the most active ADSs should be in the foragers, but this was not the case in our 20-day-old workers exposed to ID, as their more active ADSs were seriously suppressed (H2). Due to impairment of the ADS by ID, longevity [ 3 , 11 ], resistance to parasitoses [ 13 , 34 ], and harmful xenobiotics [ 35 ] may also be decreased in the foragers. Thus, decreased forager ADSs due to decreasing colony survival may impact the colony’s fitness (compare Lemanski et al [ 10 ]).…”

The Effects of Exposure to Flupyradifurone on Survival, Development, and Foraging Activity of Honey Bees (Apis mellifera L.) under Field Conditions

“…Studies have suggested that sublethal concentration of pesticides would cause transcriptional alterations involved in immune and detoxification functions in bee species [ 46 , 47 ]. The response of detoxification-related genes (such as cytochrome P450) and antimicrobial peptides [ 21 ] to chemical stress is very important for the development and survival of the host.…”

Interaction of Varroa destructor and Sublethal Clothianidin Doses during the Larval Stage on Subsequent Adult Honey Bee (Apis mellifera L.) Health, Cellular Immunity, Deformed Wing Virus Levels and Differential Gene Expression

“…At the molecular level, neonicotinoids can affect a variety of genes of honeybees with different functions, such as immunity, detoxification and neural related genes [ 18 , 19 , 20 ]. Because neonicotinoids act as neurotoxins, it is not surprising that acetylcholinesterase (AChE) levels increase in bees exposed to corn fields treated with neonicotinoids [ 21 ].…”

“…Further, clothianidin, imidacloprid and thiamethoxam increased nAChRα expression when bees were treated in the laboratory after 72 h of treatment [ 18 ]. Cytochrome P450 enzyme expression level, which is associated with detoxification, has also been shown to be increased when bees are exposed to neonicotinoids [ 19 ]. The expression of immune-related genes can be suppressed as well by neonicotinoids, possibly promoting the establishment and replication viruses [ 18 , 22 ].…”