How Far the Light Reaches: A Life in Ten Sea Creatures by Sabrina Imbler

 

"When scientists discovered the hybrid butterfly fish, they did not give it a name. Hybrids do not have Linnaean names because they are not distinct species. Many hybrids are unable to bear fertile young, if they can reproduce at all. They are expected to die out. In Linnaean taxonomy, hybrids look like algebra–two species names adjoined with an x. A hybrid threadfin butterfly fish and a lined butterfly fish becomes C. auriga x C. lineolatus."