Swordfish (Xiphias gladius) are large, highly migratory, predatory fish characterized by a long, flat bill in contrast to the smooth, round bill of the marlins...They are the sole member of their family Xiphiidae...While swordfish are cold-blooded animals, they have special organs next to their eyes to heat their eyes and also their brain. Temperatures of 10 to 15 Cﾂ≫?ｹ above the surrounding water temperature have been measured. The heating of the eyes greatly improves the vision, and subsequently improves their ability to catch prey. Out of the 25 000+ species of bony fish, only about 22 are known to have the ability to heat selected body parts above the temperature of the surrounding water. These include the swordfish, marlin, tuna and some sharks...many sources including the United States Food and Drug Administration warn about potential toxicity from high levels of methylmercury in swordfish. The FDA recommends that women who are pregnant or who may become pregnant should eat no more than one seven-ounce serving a month; others should eat no more than one serving a week.