Although tumors in zooplankton were reported in 1994 from an area of the Baltic Sea, this is the first time photographs have been taken of the abnormalities and that preliminary evidence has been presented that the tumors are cancerous. Earlier research speculated that tumors might form in zooplankton, but the organisms would die at molting before tumors would be obvious. The team found large tumors on juveniles and on young, recently molted adult zooplankton in Lake Michigan. The tumors were found in several species of copepods and Cladocera. Predatory species were more likely to have tumors than herbivorous species.
Preliminary analyses suggest that tumors are more common nearshore than offshore.
The work is the effort of a team of five scientists including Drs.