An elementary school science teacher decided to liven up the classroom with a salt-water aquarium. knowing that salt-water aquaria can be quite a hassle, the teacher proceeded stepwise. First, the teacher conditioned the water. Next, the teacher decided to stock the tank ith various marine invertebrates, including a polychaete, a siliceous sponge, several bivalves, a shrimp, several sea anemones of different types, a colonial hydra, a few coral species, an ectoproct,a sea star, and several gastropod varieties. Lastly, some vertebrates-a parrotfish and a clownfish- were added. She arranged for daily feedings of copepods and feeder fish.
One day, little Tommy (a student in an under-supervised class of 40 fifth graders) got the urge to pet Nemo (the clownfish) who was swimming amon the waving petals of a pretty underwater "flower" that had a big hole in the midst of the petals. Tommy giggled upon finding that these petals were sticky feeling. A few hours later, Tommy was in the nurse's office with nausea and cramps. Microscopic examination of hisfingers would probably have revealed the presence of