When I set essays for my first-year students to write during the semester, I try to give them a scientific paper on each topic to start them off. This means that I need to do some extra bedtime reading as I need to select those papers carefully. Today’s post is based on one of those: a paper about a fascinating mutualistic relationship between marine algae and a species of isopod (the same crustacean group as the more familiar slater).
Symbiotic relationships are fairly common in the oceans – perhaps the best-known example is the relationship between reef-building corals and a group of algae called dinoflagellates (zooxanthellae). The coral animals gain sugars from their algal partners, & may die if the algae leave (which happens if water temperatures get too high, resulting in the coral ‘bleaching’ as at least some of their colour is due to the algae). Another example of such a food-based symbiosis is the one between chemosynthetic bacteria and invertebrate animals at deep-see hot-water vents (Lindquist, Barber & Weisz, 2005). Because many bacteria & algae produce toxic chemicals as a byproduct of their metabolism, it’s been suggested that some microbe-invertebrate relationships also have an element of defence about them. Niels Lindquist & his colleagues investigated this possibility in a species of marine isopod belonging to the genus Santia.
Although these isopods represent only the second marine example of microbial symbionts producing a chemical defence against host predators, the risk of predation is high in many marine habitats, suggesting that defensive symbioses may be more common in the marine environment than presently believed.