The Symbiont

Symbiodinium are small unicellular algae (dinoflagellates) that form symbiotic associations with corals, giant clams, anemones, and other organisms. When I first heard about these organisms I was amazed that Symbiodinium reside within these organisms' cells (INSIDE THEIR CELLS!). Can you get much closer than that?

Symbiodinium enter these organisms typically through the "mouth" and are then moved to cells. At the cellular level, they are "ingested" via phagocytosis. However, the coral cell is able to distinguish Symbiodinium from other food items and therefore does not attempt to digest it. Instead, it incorporates the symbiont and begins establishing a complex relationship.... AMAZING! How does the coral know not to eat the symbiont? Does the symbiont have special markers on the outside of its cell membrane? I found a review paper on this here.

In class the other day I learnt that Dinoflagellates have genomes that are larger than that of humans! Its crazy to think that a single celled organism's instructions for life are more complex than our own!! However, when I went to look up the genome size of Symbiodinium, I saw that it is actually smaller than our own 1.5 vs 3 Billion base pairs. Why do you think that is?

That is all for today. I will get to Clade D soon.