Ostracods - via Colossal
What a cool effect!
Ostracods are the little spec-like shrimp thingies which collide with the big silver fish. Apparently when the big fish accidentally eats an ostracod, the ostracod produces a bioluminescent (i.e. glowing) chemical, which causes the predator to spit out its prey (resulting in that bright fireball effect) to avoid attracting attention to itself (i.e. note the transparent body).
(*) ... from finding that the experiment we'd planned to run might now need to be delayed while some bureaucratic process that takes 3 weeks minimum to complete, to only now stumbling across a paper which essentially had already scooped a section part of our work (but fortunately, sans results). Argh, argh argh! This sucks...