Germline Transgenesis in Ciona

A simple inland culture system provides insights into ascidian post-embryonic developmental physiology

Maintenance and breeding of experimental organisms are fundamental to life sciences, but both initial and running costs, and hands-on zootechnical demands can be challenging for many laboratories. Here, we first aimed to further develop a simple protocol for reliable inland culture of tunicate model species of the Ciona genus. We cultured both Ciona robusta and Ciona intestinalis in controlled experimental conditions, with a focus on dietary variables, and quantified growth and maturation parameters. From statistical analysis of these standardized datasets, we gained insights into the post-embryonic developmental physiology of Ciona and inferred an improved diet and culturing conditions for sexual maturation. We showed that body length is a critical determinant of both somatic and sexual maturation, which suggests the existence of systemic control mechanisms of resource allocation towards somatic growth or maturation and supports applying size selection as a predictor of reproductive fitness in our inland culture to keep the healthiest animals at low density in the system. In the end, we successfully established a new protocol, including size selection, to promote both sperm and egg production. Our protocol using small tanks will empower researchers to initiate inland Ciona cultures with low costs and reduced space constraints.

Effect of Polycyclic Aromatic Hydrocarbons on Development of the Ascidian Ciona intestinalis Type A

Polycyclic aromatic hydrocarbons (PAHs) are pollutants that exert harmful effects on marine invertebrates; however, the molecular mechanism underlying PAH action remains unclear. We investigated the effect of PAHs on the ascidian Ciona intestinalis type A (Ciona robusta). First, the influence of PAHs on early Ciona development was evaluated. PAHs such as dibenzothiophene, fluorene, and phenanthrene resulted in formation of abnormal larvae. PAH treatment of swimming larva induced malformation in the form of tail regression. Additionally, we observed the Cionaaryl hydrocarbon receptor (Ci-AhR) mRNA expression in swimming larva, mid body axis rotation, and early juvenile stages. The time correlation between PAH action and AhR mRNA expression suggested that Ci-AhR could be associated with PAH metabolism. Lastly, we analyzed Ci-AhR mRNA localization in Ciona juveniles. Ci-AhR mRNA was localized in the digestive tract, dorsal tubercle, ganglion, and papillae of the branchial sac, suggesting that Ci-AhR is a candidate for an environmental pollutant sensor and performs a neural function. Our results provide basic knowledge on the biological function of Ci-AhR and PAH activity in marine invertebrates.