Diadumene franciscana

This species is a simple, solitary ascidian, with a tough leathery outer covering or tunic. The body is ovoid in shape, measures up to 5 cm in length, and attaches to the substrate near its base. Oral siphon is positioned anteriorly; atrial siphon is located midcenter, often projecting at a right angle. Tips of both siphons are conspicuously ringed in alternating white and dark red bands. Internally, the siphons possess distinct, short siphonal spines, with each spine characterized by a rounded, serrated edge. Overall, the tunic is tannish-brown with bright orange or red markings, but often covered with very short hairs and debris.

This species is a simple, solitary ascidian, with a tough outer covering or tunic. The body is globular to ovoid in shape, measures 1-2 cm in diameter, and attaches to the substrate at its base. The oral and atrial siphons are positioned anteriorly, well separated, and characterized by tentacle-like processes around the openings (oral siphon 6-lobed; atrial siphon 4-lobed). Overall, the tunic is translucent to greyish-green in color; the surface is sparsely covered with very short hairs that typically remain free of sand grains or debris.

Microcosmus squamiger has been introduced to the Northeast Pacific, with confirmed records in southern California and Baja California Mexico. In addition, this species has been introduced to other locations around the world, including the Northeast Atlantic, the Mediterranean, and South Africa. It is native to southern Australia.

Molgula citrina has been found recently in south-central Alaska (Lambert et al. 2010). It remains unclear whether this record represents a new invasion or a previously overlooked circumpolar distribution. The species is native to the North Atlantic, with a wide geographical distribution ranging from northeast North America to Great Britain and northern Europe.

Microcosmus squamiger is most similar to M. exasperatus Heller, 1878, a species that presently is not found in the Northeast Pacific.

In the Northeast Pacific, Molgula manhattensis is most similar to other molgulid tunicates, including M. retortiformis Verrill, 1871 and another non-native species found in the region, M. manhattensis (De Kay, 1843).