A Larvacean

A Larvacean (Oikopleura) Urochordata

Location: 100 km offshore from Barnegat, NJ. Depths of >200 meters. Caught while drifting a plankton net (365 micrometer mesh) from the back of a boat at night. Summer 2009.

Notes: Larvaceans, also known as appendicularians, are chordates (Urochordata) related to sea squirts. The animal pictured secretes a hollow mucous “house” around itself and uses its tail (on the right) to create a current through the house that provides propulsion. A series of mucous filters strain micro-organisms from this current to feed the larvacean. The houses are replaced periodically and are quickly jettisoned if the animal is disturbed, as invariably occurs when they are captured in plankton nets. The animal shown here is less than 0.5 mm long, but the house may reach several millimeters.

Oikopleura is the most common nearshore larvacean, usually found in clear, high-salinity waters. This specimen was caught well offshore, but they are occasionally caught nearshore or even in high salinity bays.

Collected by: Bill Johnson, Goucher College.