The abundant pelagic tunicate Salpa thompsoni is a major grazer in the Southern Ocean (SO) with high ingestion rates, fast-sinking faecal pellets, and the potential to rapidly grow and form dense blooms. We investigated the length-frequency distribution, maturity stage composition, growth, development speed, and size-specific diel vertical abundance patterns at one of the northernmost habitats of S. thompsoni (Chatham Rise, east of New Zealand, ~ 44°S 178°E). By observing the in situ growth of distinct size cohorts and ex situ on-board experiments, relative growth was estimated for 6–10 mm blastozooids to be between 8.8–11.7% d−1 at ambient temperatures of 10 °C, with good agreement between our cohort-based field estimates and ex situ growth chambers. Transition times between development stages were estimated to be 3.8 ± 1.5 days, allowing for the succession from newly released aggregate chain to functional male blastozooid within 23 days. Integrative Bongo tows in the upper 200 m showed that S. thompsoni not only have daytime-dependent vertical abundance patterns, but also that these are size-specific, with medium-sized blastozooids and large oozooids contributing most to the elevated values during the night. The present study highlights the need for more in-depth biological studies of S. thompsoni at lower latitudes, which will help in understanding their increasingly structuring role in a gradually warming SO.

中文翻译：

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新西兰查塔姆隆起的 Salpa thompsoni 生物学：人口统计学、生长和垂直迁移

丰富的远洋被囊动物 Salpa thompsoni 是南大洋 (SO) 的主要食草动物，具有高摄取率、快速下沉的粪便颗粒以及快速生长和形成密集花朵的潜力。我们调查了 S. thompsoni 最北端栖息地之一的长度频率分布、成熟阶段组成、生长、发育速度和特定尺寸的日粮垂直丰度模式（新西兰东部查塔姆隆起，~ 44°S 178° E)。通过观察不同大小队列的原位生长和异位机载实验，在 10 °C 的环境温度下，6-10 毫米胚泡的相对生长估计在 8.8-11.7% d-1 之间，两者之间具有良好的一致性我们基于队列的实地估计和异地生长室。开发阶段之间的过渡时间估计为 3.8 ± 1.5 天，允许在 23 天内从新释放的聚合链继承到功能性雄性胚泡。上层 200 m 的综合 Bongo 拖曳表明，S. thompsoni 不仅具有依赖于白天的垂直丰度模式，而且这些模式具有特定大小，中型胚泡和大型卵形虫对夜间值的升高贡献最大。本研究强调需要对低纬度的 S. thompsoni 进行更深入的生物学研究，这将有助于了解它们在逐渐变暖的 SO 中日益增长的结构作用。中型胚泡和大型虫卵对夜间值升高的贡献最大。本研究强调需要对低纬度的 S. thompsoni 进行更深入的生物学研究，这将有助于了解它们在逐渐变暖的 SO 中日益增长的结构作用。中型胚泡和大型虫卵对夜间值升高的贡献最大。本研究强调需要对低纬度的 S. thompsoni 进行更深入的生物学研究，这将有助于了解它们在逐渐变暖的 SO 中日益增长的结构作用。