I see that in WoRMS, P. gracilum / gracile is now an unaccepted junior synonym of fragile. I'm not familiar enough with ascidian taxonomy to know who synonymised the Australian P. gracilum (gracile) with the Japanese P. fragile, or why, but from a non-taxonomist's view, may I say that this looks almost exactly like the photo of P. gracilum that Neville Coleman collected from Kangaroo Island in 1978, and was described by Pat Mather (Kott). Time to read the descriptions!