Unusual Mating Habit of Anglerfish

03 May 2007

Extreme water pressures, lack of sunlight and turbulent water make some deep sea fish come up with strange shapes and behaviors to survive. Anglerfish is famed for its luminescent spine, acting like a bait to "fish" its prey. However, individuals are locally rare and encounters doubly so, finding a mate is problematic. When scientists first started capturing anglerfish, they noticed that all of the specimens were females. These were a few inches in size and almost all of them had what appeared to be parasites attached to them.

It turns out, these "parasites" are the remains of male anglerfish! At birth, male anglerfish are already equipped with extremely well developed sensory organs that detect scents in the water. They have no digestive system, and thus are unable to feed independently. They must find a female anglerfish, and quickly, or else they will die.

The sensitive organs help the male to detect the pheromones that signal the proximity of a female anglerfish. When he finds a female, he bites into her flank, and releases an enzyme which digests the skin of his mouth and her body, fusing the pair down to the blood vessel level. The male then atrophies into nothing more than a pair of gonads that release sperm in response to hormones in the female's bloodstream indicating egg release.

This is an extreme example of sexual dimorphism. However, it ensures that when the female is ready to spawn, she has a mate immediately available.