Male anglerfish grows in the dark depths of the sea, moving slowly, much smaller than the female, and do not live in groups, in the vast ocean male fish is difficult to find female fish, once encountered female fish, bite through the female abdominal tissues, drilling into the skin, life-long attached to the death of males, male life-long nutrition is also supplied by the female fish. Over time, the anglerfish has developed this unique mate relationship.

Pipefish - males parasitize females

For years, scientists couldn't understand why only female pipefish were found. To make matters even more bizarre, all the females had strange lumps rising from their sides.

After studying them, researchers found that the lumps were the remains of parasitic male pipefish. Male pipefish are very small and lose their digestive system when they are long enough to mate. In the pipefish population with the scientific name Photocorynus Spiniceps, males are only 0.25 inches (about 6.35 millimeters) long, making them one of the smallest known vertebrates.

In comparison, females reach 50 times the size of males.

Pipefish - males parasitize females

To survive, male pipefish must find a female and parasitize her body. They bite the female, releasing an enzyme that dissolves the skin tissue, which in turn bonds them to the female.

In this way, the male's semen enters the female's body while gaining access to her nutrients. However, the male fish quickly heads for death, leaving only a mass of testicles ready to fertilize the eggs when the female ovulates.

Scientists have found female pipefish with eight clusters of testicles. For those males that don't find a female, they take another approach, which is to change sex into a female and wait for a male to show up.

The mating behavior of the striped anglerfish is brief and interesting. The female excretes a number of gelatinous eggs in sheets, which are used to attract the male's sperm, which floats with the water. The fertilized eggs then rise to the surface for a few days before sinking to the bottom until the fetus hatches. The few monkfish found off the coast of southern Australia mate in a different way. The smooth-skinned females lay fewer but larger eggs than other species of monkfish. After mating, one party cares for the fertilized eggs until they hatch into fish. The guardian male or female uses the plump, attractive eggs to lure in curious prey and devour them in one fell swoop. Monkfish are found in tropical and subtropical waters around the globe, yet this prey-sneaky fish still needs human protection as its habitat deteriorates.

The monkfish's breeding season is usually in the spring and summer. The eggs laid by females can cluster to form gelatinous, sheet-like clusters up to 9 meters long and 3 meters wide, which float on the surface until they hatch out as larvae. The newly hatched pipefish larvae are protected by a gelatinous outer membrane. Both males and females develop on the surface of the sea and feed on plankton, so the juveniles do not yet have a "fishing rod" structure. When the development to a certain extent, the male fish will choose a suitable female fish, bite through the female's abdominal tissue and attached to it. The female's tissue grows rapidly and soon wraps around the male. Finally, the female sinks to the bottom of the ocean with the male parasitized in her body, and begins their benthic life in the "two-fish world".