Sigmund Freud studied the sex lives of eels.

While enrolled at the University of Vienna, a young Freud studied zoology. On a research trip to Trieste to study the sexual organs of eels, his professor assigned him the task of finding the gonads of the male of the species, a discovery that had eluded scientists for centuries. Freud spent many hours dissecting eels to no avail. "All the eels I have cut open are of the tenderer sex," he reported.