Description
Chaetoceros/Vorticella (CV) is a fascinating planktonic consortium consisting of Chatoceros diatoms and Vorticella ciliates. CV is found in unexpected locations, for example in the nutrient-depleted tropical oceans where neither of the components would be likely to thrive. The symbiosis may provide additional benefits to the partners such as protection from predation by copepods and fish larvae.
Both components of CV are tiny. Chaetoceros colonies may be 1 mm in length, while a Vorticella cell is merely 0.1 mm long. It is surprising that they are able to form well-organized arrangements of up to 30 Vorticella on one ""carrier"" Chaetoceros. When assembled, the Vorticella exert stochastic rapid contractions probably in response to hydrodynamic perturbations. This allows the CV to swim and possibly to reach regions rich in light where it will conduct its photosynthesis.
Research has produced a multitude of observations of CV that now need to be interpreted and analyzed mathematically. The most straightforward hypothesis to be tested is that CV forms by accidental association of sticky Vorticella. An alternative hypothesis is that once a single association has formed, replication of both partners is the main maintenance mechanism.
Tasks and Responsibilities
Mathematical models exist for randomly distributed and randomly swimming ""predator"" and ""prey"" meeting each other and a possible successful capture of the prey by the predator. It will be the students task to search the literature and to adapt the results to our situation. This is made more difficult since the Vorticella do not swim on straight lines as is usually assumed in the models, but rather in spirals. Likewise, the Chaetoceros may change its behavior as it becomes increasingly populated with Vorticella. After the encounter the Vorticella also needs to attach successfully. In order to test any analytical results, Ben will create simulations with an Individual-based Model (IBM). These simulations can be considered as ""little films"" that then point to testable hypotheses.
Once the consortium has been formed, it's necessary to investigate what advantages it has over the unassociated partners. In the films we see that the consortium performs a ""hopping and sinking"" motion.