Dataset for: Effects of two neonicotinoid insecticides on blood cell profiles and corticosterone concentrations of wood frogs (Lithobates sylvaticus)

Neonicotinoids are widely used insecticides that are detectable in agricultural waterways. These insecticides are of concern due to their potential impacts on non-target organisms. Pesticides can affect development of amphibians and suppress the immune system, which could impact disease susceptibility and tolerance. No previous studies on amphibians have examined the effects of these insecticides on differential blood cell proportions or corticosterone concentrations (a general stress hormone). We investigated the effects of chronic exposure to two neonicotinoids, thiamethoxam and clothianidin, on immunometrics of wood frogs (Lithobates sylvaticus). Frogs were exposed to single, chronic treatments of 2.5 µg/L or 250 µg/L of clothianidin or thiamethoxam for seven weeks from Gosner stage 25 to 46. The juvenile frogs were then maintained for three weeks post-metamorphosis without exposure to neonicotinoids. We measured water-borne corticosterone twice: six days and eight weeks after exposure in larval and juvenile frogs respectively. We assessed differential blood cell profiles from juvenile frogs. Corticosterone was significantly lower in tadpoles exposed to 250 µg/L of thiamethoxam compared to other tadpole treatments, but no significant differences in corticosterone concentrations were found in treatments using juvenile frogs. Anemia was detected in all treatments compared to controls with the exception of tadpoles exposed to 2.5 µg/L of clothianidin. Neutrophils to leukocyte and neutrophil to lymphocyte ratios were elevated in frogs exposed to 250 µg/L of thiamethoxam. Collectively, these results indicate that chronic exposure to neonicotinoids has varied impacts on blood cell profiles and corticosterone concentrations of developing wood frogs, indicative of stress. Future studies should investigate whether exposure to neonicotinoids increases susceptibility to infection by parasites in both larval and adult wood frogs.

新烟碱类杀虫剂（Neonicotinoids）是一类广泛应用的杀虫剂，可在农业水域中被检出。这类杀虫剂因对非靶标生物存在潜在危害而备受关注。农药可影响两栖动物的生长发育，并抑制其免疫系统，进而可能改变宿主对疾病的易感性与耐受能力。目前尚无针对两栖动物的研究探讨此类杀虫剂对血细胞比例差异或皮质酮（corticosterone，一种通用应激激素）浓度的影响。本研究探究了慢性暴露于两种新烟碱类杀虫剂——噻虫嗪（thiamethoxam）与噻虫胺（clothianidin）——对林蛙（Lithobates sylvaticus）免疫代谢特征的影响。研究人员将处于Gosner发育分期25至46期的林蛙，分别暴露于2.5 μg/L或250 μg/L的噻虫胺或噻虫嗪，进行为期7周的单一慢性处理；随后将变态完成后的幼蛙置于无新烟碱类杀虫剂暴露的环境中饲养3周。我们分别在蝌蚪期和幼蛙期，于暴露结束后6天和8周两次检测水体中的皮质酮含量，并对幼蛙的血细胞分类谱进行了分析。结果显示，与其他处理组蝌蚪相比，暴露于250 μg/L噻虫嗪的蝌蚪体内皮质酮水平显著降低，但幼蛙组的皮质酮浓度未出现显著组间差异。除暴露于2.5 μg/L噻虫胺的蝌蚪外，其余所有处理组蝌蚪均较对照组出现贫血症状。暴露于250 μg/L噻虫嗪的林蛙，其中性粒细胞与白细胞比值、中性粒细胞与淋巴细胞比值均显著升高。综上，慢性暴露于新烟碱类杀虫剂会对发育中的林蛙的血细胞谱与皮质酮浓度产生多样影响，提示存在应激效应。未来研究可探讨新烟碱类杀虫剂暴露是否会提升幼虫期与成虫期林蛙对寄生虫感染的易感性。