Current thinking on how the Toxoplasma gondii parasite invades its host is incorrect, according to a study published today in Nature Methods describing a new technique to knock out genes. The findings could have implications ...
Definition. Coral bleaching is a process whereby the coral colonies lose their colour, either due to the loss of pigments by microscopic algae (zooxanthellae) living in symbiosis with their host organisms (polyps), or because these zooxanthellae have been expelled.
This stress causes corals to expel their zooxanthellae, which leads to a lighter or completely white appearance, hence the term bleached. Bleaching has been attributed to a defense mechanism in corals; this is called the adaptive bleaching hypothesis, from a 1993 paper by Robert Buddemeier and Daphne Fautin. Bleached corals continue to live. But the algae provide the coral with 90% of its energy, after expelling the algae the coral begins to starve.