Molgula pugetiensis is a Pacific tailless ascidian within the Roscovita clade of molgulids., Swalla Billie J and Maliska Max E, The Biological bulletin, 2010 Dec, Volume 219, Issue 3, p.277-82 (2010)
The molgulid ascidians are a monophyletic group of tunicates that share specific morphological features, including a heart/kidney complex and hermaphroditic gonads found on both sides of the adult. The larval body plan, however, is quite plastic, with tailless species evolving at least four times independently within the molgulids. The Roscovita clade of molgulid ascidians includes three species that are found sympatrically in Roscoff, France, and includes both tailed and tailless species. Another species in this clade, Molgula pacifica, is a direct developing tailless molgulid ascidian within the Roscovita clade found on the outer coast of Vancouver Island. M. pacifica "larvae" never hatch, and they undergo metamorphosis within the chorion. Molgula pugetiensis is a molgulid ascidian found in the San Juan Islands, but its development has not been reported. Here, we show that this species, belonging to the Roscovita clade, is a tailless ascidian species with "larvae" that hatch from the chorion before metamorphosis, similar to the well-described tailless Molgula occulta from Roscoff, France. Immediately after hatching, the tailless larvae develop ampullae and proceed to metamorphose into juveniles.