Aquatic insects are well adapted to freshwater environments, but the molecular basis of these adaptations remains largely unknown. Most firefly species (Coleoptera: Lampyridae) are terrestrial, but the larvae of several species are aquatic. Here, larval and adult transcriptomes from Aquatica leii (freshwater) and Lychnuris praetexta (terrestrial) were generated to test whether the genes associated with metabolic efficiency and morphology have undergone adaptive evolution to fresh water. The aquatic fireflies had a significantly lower ratio of nonsynonymous to synonymous substitutions than the terrestrial insects, indicating a genomewide evolutionary constraint in the aquatic fireflies. We identified 341 fast‐evolving genes and 116 positively selected genes in the aquatic fireflies. Of these, 76 genes exhibiting both fast evolution and positive selection were primarily involved in ATP production, energy metabolism and the hypoxia response. We identified 7,271 differentially expressed genes (DEGs) in A . leii (adults versus larvae) and 8,309 DEGs in L . praetexta (adults versus larvae). DEGs specific to the aquatic firefly (n  = 1,445) were screened via interspecific comparisons (A . leii versus L . praetexta ) and were significantly enriched for genes involved in metabolic efficiency (e.g., ATP production, hypoxia, and immune responses) and certain aspects of morphology (e.g., cuticle chitin, tracheal and compound eye morphology). These results indicate that sequence and expression‐level changes in genes associated with both metabolic efficiency and morphological attributes related to the freshwater lifestyle contributed to freshwater adaptation in fireflies. This study provides new insights into the molecular mechanisms of aquatic adaptation in insects.

中文翻译：

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萤火虫（鞘翅目：兰科）的比较转录组学分析，以探索对淡水的分子适应性。

水生昆虫很好地适应了淡水环境，但是这些适应的分子基础仍然未知。多数萤火虫种类（鞘翅目：Lampyridae）是陆生的，但某些种类的幼虫是水生的。在这里，来自淡水（Aquatica leii）和淡水荔枝（Lychnuris praetexta）的幼虫和成虫转录组（地面）生成以测试与代谢效率和形态相关的基因是否已经适应淡水进化。水生萤火虫的非同义替换与同义替换的比率比陆地昆虫低得多，这表明水生萤火虫存在全基因组进化限制。我们在水生萤火虫中鉴定了341个快速进化的基因和116个阳性选择的基因。在这些基因中，有76个显示快速进化和阳性选择的基因主要参与ATP的产生，能量代谢和缺氧反应。我们在A中鉴定了7,271个差异表达基因（DEG）。 leii（成人对幼虫）和在8309度的视角大号。 文字（成人与幼虫）。DEGS特定于水生萤火虫（Ñ  = 1445）经间比较筛选（甲。 leii与大号。 praetexta）和显著富集参与代谢效率的基因（例如，ATP生产，缺氧，和免疫应答）和某些方面形态（例如角质层甲壳质，气管和复眼形态）。这些结果表明，与代谢效率和与淡水生活方式有关的形态属性相关的基因的序列和表达水平的变化有助于萤火虫适应淡水。这项研究提供了对昆虫水生适应分子机制的新见解。