“…As in many other sedentary marine organisms, symbiotic bacteria are known to reside in tunicates and are also known as tissue-associated, such as in endodermal tissues, the pharynx, the tunic and the intestine ( Behrendt et al, 2012 ; Dishaw et al, 2014 ). The ascidian microbiota contributes to nutrition via photosynthesis ( Donia et al, 2011 ; López-Legentil et al, 2011 ; Hirose, 2015 ), production of secondary metabolites ( Schmidt, 2014 ; Tianero et al, 2015 ; Chen et al, 2018 ), nitrification ( Martínez-García et al, 2008 ; Erwin et al, 2014 ), protection against biofouling, predation ( Degnan et al, 1989 ; Paul et al, 1990 ; Fu et al, 1998 ; Vervoort et al, 1998 ; Faulkner, 2001 ; Schreiber et al, 2016 ), vanadium accumulation ( Ueki et al, 2019 ), and the host immune response ( Liu et al, 2021 ).…”