Breadth versus depth of knowledge: the need for new model trematode species.

The growth of knowledge and research practices in any discipline is characterised by a trade-off between depth and breadth: we can either invest efforts to learn a little about many things, or learn a lot about few things. In parasitology, breadth of knowledge corresponds to research on biodiversity and taxonomy: the discovery and description of an increasing number of new species. In contrast, depth of knowledge comes from focused research on a few model species, about which we accumulate much detailed information. Breadth and depth of knowledge are equally important for progress in parasitology. In this essay, focusing on trematodes, I demonstrate that current research is rapidly broadening our knowledge (high rate of new trematode species being discovered) but not deepening that knowledge at a comparable rate. The use of model species, with caveats, appears to offer a promising avenue for deeper knowledge. I present a case study illustrating how it is possible to develop new model trematode species at low cost to increase the depth of our understanding in areas including host-parasite ecological dynamics, co-evolution, and responses to environmental and climatic changes. The take-home message serves as a call to action to parasitologists, emphasising the need to focus as much effort on depth of knowledge as we currently invest in breadth of knowledge.