At times, this tiny pelagic tunicate can be among the more abundant gelatinous animals in offshore waters, but most people have no idea of its presence.  With a body length of only 1 mm, it's easy to see why Oikopleura is usually overlooked.  In Monterey Bay and other West Coast locations, this larvacean may occasionally be found in surface aggregations that form long parallel rows - individuals appear as closely spaced reddish specks.  Oikopleura has the typical larvacean tadpole-like appearance with a tail that is 3 to 4 times the length of the body.  When undisturbed, it produces 5 to 10 pea-sized mucous webs (the "house") a day that are used for feeding, protection and buoyancy.  The house concentrates tiny food particles, which are transferred to the mouth for ingestion.  Discarded houses are capable of producing bluish-green bioluminescent flashes, and also make a significant contribution to the steady rain of organic material (known as marine snow) that slowly descends into deeper water.   Various species of Oikopleura are distributed throughout tropical and temperate seas.  In boreal and Arctic waters, O. dioica is replaced by the more cold tolerant and larger O. vanhoeffeni and O. labradoriensis.  

All photographs © David Wrobel and may not be used or copied without permission!