Anglerfish Fuse When They Mate

If humans were like anglerfish, breaking off a relationship would be more than difficult — it would be life-threatening. That’s because anglerfish undergo a stark physical transformation when they mate, fusing together for life as part of a biological concept known as sexual parasitism.

Of the more than 300 species of anglerfish, sexual parasitism is only found in certain species that reside in the deep sea. These fish also experience sexual dimorphism, in which different genders have starkly different physical appearances; in this case, female anglerfish are much larger than their male counterparts. 

When searching for a mate, males use their sense of smell to track down females. Once they’ve found a mate, the males latch on with their small, sharp teeth — essentially becoming irremovable appendages. Males then drain resources from the females for life, occasionally fertilizing eggs along the way.