The seabird tick, Ixodes uriae, is a significant ectoparasite of penguins in Antarctica and of other seabirds, mainly in coastal, polar regions of the Northern and Southern hemispheres, but the tick’s distribution extends into more temperate regions as well. The expansive range of this tick suggests that it is exposed to a wide range of abiotic stresses, including dehydration, heat, and cold. To better understand how I. uriae responds to stress exposure, we examined cross-tolerance between dehydration and thermal stress based on survival analyses and used RNA-seq to monitor transcriptional responses to cold, heat, and dehydration. Slight dehydration improved cold, but not heat tolerance, whereas severe dehydration reduced subsequent thermal tolerance. Dehydration exposure prompted transcript-level shifts underlying protein metabolism, recovery from stress, and processes allowing subsequent rehydration by water vapor uptake. Both cold and heat stress yielded expression changes involved in cuticle modification. One gene increased in expression (enzyme P450) and one decreased (transcription factor Hairy) in response to all three stresses. This study provides the groundwork for assessing stress tolerance in this bipolar ectoparasite.

海鸟蜱（Ixodes uriae）是南极洲企鹅和其他海鸟的重要体外寄生虫，主要分布在北半球和南半球的沿海极地地区，但蜱的分布也延伸到更温和的地区。这种蜱的广泛范围表明它暴露于广泛的非生物胁迫，包括脱水、热和冷。为了更好地了解I. uriae对压力暴露做出反应，我们根据生存分析检查了脱水和热应激之间的交叉耐受性，并使用 RNA-seq 监测对冷、热和脱水的转录反应。轻度脱水提高了耐寒性，但不改善耐热性，而严重脱水降低了随后的耐热性。脱水暴露促使蛋白质代谢、从压力中恢复以及随后通过水蒸气吸收进行补液的过程中的转录水平变化。冷和热应激都产生了与角质层修饰有关的表达变化。响应所有三种压力，一种基因表达增加（酶 P450），一种基因表达减少（转录因子 Hairy）。这项研究为评估这种双极体外寄生虫的压力耐受性提供了基础。