"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

September 26, 2011

Parvilucifera sinerae

Phytoplankton are microscopic single-celled "plants" which float in the upper surfaces of the ocean, and their photosynthetic action is responsible for generating most of the oxygen in our atmosphere. While you might think that something so tiny would not be host to anything, there are in fact a myriad array of viruses, bacteria, and flagellate organisms that infect and exploit phytoplankton, and the parasite for today is one of them. Parvilucifera sinerae is a single-celled, flagellated organism which infects dinoflagellate algae such as Alexandrium minutum. The photo shows an infected A. minutum cell. While earlier in this post we extolled the virtue of phytoplankton, dinoflagellate algae are also known to be responsible for harmful algal bloom events such as "Red Tides", so there is a lot of interest in their ecology and the factors that can influence their likelihood of blooming.

For P. sinerae, infecting its host is not an easy task - not only does it have to find a swarm of its tiny host in the vast ocean, it also needs to make contact and accomplish what amounts to a cellular heist - the parasite needs to break through the protective shell of the alga in order to steal its valuable content. As you can imagine, during such an intense operation, being jostled around will probably throw you off your game. And indeed that is what a group of scientists in Spain have found. It appears that even a slight turbulence is enough to reduce the infection success of P. sinerae and that it performs best under calm, still conditions. These researchers suggested that turbulence would erode the zone of chemical emission around the dinoflagellate, making them more difficult to detect. Turbulence would also shorten the period of time which P. sinerae are in constant contact with the host cell - which is a necessary precondition for the parasite to perform its little cellular heist.

While both P. sinerae and its host are tiny, their interactions can have far-reaching ecological consequences, and as explained earlier they are among the most important organisms on the planet. In addition, parasitic killers, such as today's parasite, have been suggested as a possible biological control for harmful algal blooms, but it is like that the effectiveness of any such control would be at the mercy of environmental factors such as small-scale marine turbulence.

Image from figure of the paper.

Llaveria, G., Garcés, E., Ross, O.N., Figueroa, R.I., Sampedro, N. and Berdalet, E. (2010) Small-scale turbulence can reduce parasite infectivity to dinoflagellates. Marine Ecology Progress Series 412: 45-56.


  1. Heading to the ocean this week, I can't help but be intrigued by this post about Parvilucifera sinerae. Is this a fungus that is harmful to humans, and also, What are the chances and consequences of bringing this back to our environment by means of swimming gear and clothing?

  2. Very interesting! Thinking about this tiny parasite finding its tiny host made my day. Science is fascinating.

  3. How interesting! I’ve never heard of a protist being a parasite of another protist, especially in that type of environment.