Molecular identification of reproductive cells released from Cypassis irregularis Nigrini (Radiolaria)

The mechanisms of the extensive distribution of radiolarian-affiliated sequences from clone libraries of marine picoeukaryotes from deeper water remain poorly understood. Here, we describe an event that could explain this phenomenon. A polycystine radiolarian species, Cypassis irregularis Nigrini, released a large number of pico-size cells under culture conditions. The diameters of the cells averaged ∼3 µm and the 18S rDNA sequences fell within those of typical radiolarian families. This finding suggests that the radiolarian sequences found in the picoeukaryote size fraction from deep water are from swarmers or gametes released for reproduction. Thus, the deep ocean is expected to aid in the widespread dispersal of the genetic material of eukaryotes.