Calanus finmarchicus

 Calanus finmarchicus, a tiny copepod that drifts in seawater, eats an even tinier organism – a type of photosynthetic plankton called Alexandrium fundyense. The problem that C. finmarchicus faces is that these plankton are poisonous, producing toxins that induce paralytic shellfish poisoning, a human illness caused by eating contaminated seafood. Although previous studies suggested that C. finmarchicus is highly tolerant of the poison, new research from University of Hawaii at Manoa, USA, shows that the copepod actually gets stressed by the toxic plankton. In lab tests, even low doses of A. fundyense negatively affected the copepod’s growth and reproduction. These findings could have implications for fisheries as C. finmarchicus is a key food source for you fish.