Two-Headed Sharks Keep Popping Up—No One Knows Why

Two-headed sharks may sound like a figment of the big screen, but they exist—and more are turning up worldwide, scientists say. A few years ago off Florida, fishermen hauled in a bull shark whose uterus contained a two-headed fetus. In 2008, another fisherman discovered a two-headed blue shark embryo in the Indian Ocean. And a 2011 study described conjoined twins discovered in blue sharks caught in the Gulf of California and northwestern Mexico. Blue sharks have produced the most recorded two-headed embryos because they carry so many babies—up to 50 at at time, says study leader Felipe Galván-Magaña, of the National Polytechnic Institute in Mexico. Nicolas Ehemann, a master’s student at the National Polytechnic Institute in Mexico, believes that if the two-headed fetuses are more prevalent in nature, then overfishing is a strong culprit as it may cause the gene pool to shrink. Read the rest here 09:03