Vertical distribution of maturity stages of Oikopleura dioica (Tunicata, Appendicularia) in the frontal system off Valdes Peninsula, Argentina

A differential pattern of vertical distribution of maturity stages of Oikop leura dioica was detected in the coastal thermal frontal system off Valdes Peninsula (Argentina). The highest densities of all maturity stages as well as the highest chlorophyll a concentrations were recorded in surface water s of the transitional zone of the front. In the stratified zone, maximum de nsities of O. dioica were found in deeper layers, corresponding to thermocl ine depth. Mixed waters showed lower densities, here immature and intermedi ate stages were homogeneously distributed throughout the water column, wher eas mature animals were concentrated in surface waters, where they probably spawn.