Ascidians (phylum Chordata, class Ascidiacea) represent the closest living invertebrate relatives of the vertebrates and constitute an important model for studying the evolution of chordate development. The solitary ascidian Polycarpa mytiligera exhibits a robust regeneration ability, unique among solitary chordates, thus offering a promising new model for regeneration studies. Understanding its reproductive development and establishing land-based culturing methods is pivotal for utilizing this species for experimental studies. Its reproduction cycle, spawning behavior, and developmental processes were therefore studied in both the field and the lab, and methods were developed for its culture in both open and closed water systems. Field surveys revealed that P. mytiligera’s natural recruitment period starts in summer (June) and ends in winter (December) when seawater temperature decreases. Laboratory experiments revealed that low temperature (21 °C) has a negative effect on its fertilization and development. Although spontaneous spawning events occur only between June and December, we were able to induce spawning under controlled conditions year-round by means of gradual changes in the environmental conditions. Spawning events, followed by larval development and metamorphosis, took place in ascidians maintained in either artificial or natural seawater facilities. P. mytiligera’s fast developmental process indicated its resemblance to other oviparous species, with the larvae initiating settlement and metamorphosis at about 12 h post-hatching, and reaching the juvenile stage 3 days later. Polycarpa mytiligera can be induced to spawn in captivity year-round, independent of the natural reproduction season. The significant advantages of P. mytiligera as a model system for regenerative studies, combined with the detailed developmental data and culturing methods presented here, will contribute to future research addressing developmental and evolutionary questions, and promote the use of this species as an applicable model system for experimental studies.

中文翻译：

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孤生海鞘 Polycarpa mytiligera 的产卵诱导、发育和培养，这是一种新兴的再生研究模型。

海鞘类（脊索动物门，海鞘纲）代表了脊椎动物最接近的现存无脊椎动物亲戚，并构成了研究脊索动物发育进化的重要模型。孤生海鞘 Polycarpa mytiligera 表现出强大的再生能力，这在孤生脊索动物中是独一无二的，从而为再生研究提供了一个有前景的新模型。了解其生殖发育和建立陆基培养方法对于利用该物种进行实验研究至关重要。因此，在野外和实验室研究了其繁殖周期、产卵行为和发育过程，并开发了在开放和封闭水系统中培养其的方法。实地调查显示，P. mytiligera 的自然补充期从夏季（6 月）开始，到冬季（12 月）海水温度降低时结束。实验室实验表明，低温（21℃）对其受精和发育有负面影响。虽然自发产卵事件仅发生在六月至十二月之间，但我们能够通过环境条件的逐渐变化，在全年受控条件下诱导产卵。在人工或天然海水设施中饲养的海鞘中发生产卵事件，随后是幼虫发育和变态。P. mytiligera 的快速发育过程表明其与其他卵生物种相似，幼虫在孵化后约 12 小时开始定居和变态，并在 3 天后达到幼虫阶段。Polycarpa mytiligera 可以全年在圈养条件下诱导产卵，与自然繁殖季节无关。P. mytiligera 作为再生研究模型系统的显着优势，结合这里介绍的详细发育数据和培养方法，将有助于解决发育和进化问题的未来研究，并促进该物种作为适用模型系统的使用用于实验研究。