Classification: Unlisted Invasive Species
aquatic managers ask the public to report sightings of tunicates
and other aquatic invasive species. To report sightings contact:
Aquatic nuisance species coordinator for WDFW
WDFW Assistant aquatic nuisance species coordinator
Molgula manhattensis is a solitary tunicate (or ”sea squirt”) that is native to most of Europe, ranging from Norway to Portugal and the North American Atlantic from Maine to Texas. It is not native to Pacific Northwest waters. It has a cylindrical to irregular, grape-like shaped, up to about one inch in diameter, somewhat transparent, gray to greenish, and covered with fibrils that may or may not be attached with silt and other organic debris or other small organisms. At the free end of the tunicate, there are two siphons that are used for feeding and gamete dispersal, an incurrent, 6 lobed siphon and an excurrent 4 lobed siphon.
M. manhattensis can be found from intertidal to 300 feet deep prefers protected marine waters and estuaries and is very tolerant of pollution. It can attach to a variety of surfaces including gravel, sand, seeweed, pilings, docks. Marinas, piers, other maritime structures, and shellfish aquaculture are ideal habitats for the Sea grape tunicate where it can compete for food and space.
M. manhattensis pumps water in through the incurrent siphon, filters out oxygen and feeds on small organisms such as phytoplankton, zooplankton, oyster and mussel larvae, and other suspended organic materials, and then pumps the water as waste out through the excurrent siphon.
Like all sea squirts, M. manhattensis is hermaphroditic, meaning that it contains both male and female organs. However the male and female parts of each individual do not mature at the same time, so it does not self fertilize. Eggs and sperm are broadcast spawned in the water column producing planktonic, tadpole-like, larvae that can survive for only a few days unless a suitable substrate is found to attach to where it then metamorphoses into an adult.
See the Tunicate information page for more information.