How Do Angler Fish Reproduce?

The dark depths of the ocean present numerous challenges for the species living there, including the angler fish. Considered one of the most unusual-looking creatures in the sea, anglers have adapted to the cold and sparsely populated bottom of the ocean through their hunting, feeding and reproductive practices. To understand the reproduction of angler fish, it is necessary to appreciate their basic anatomy and feeding methods.

  1. Females

    • The females of the species are substantially larger than their male counterparts. In one species, the female can reach over 15 inches, while another species gets no larger than four inches. Female anglers feature the rod projecting from the top of its head that gives the species its name. The rod -- with bacteria inside that cause it to glow in the dark -- serves as a lure to other fish. The angler then uses her expandable mouth and inverted, spiky teeth to swallow her prey whole. Since anglers can swallow a fish up to twice their size, the dearth of food is still manageable.

    Males

    • Male angler fish often measure less than one-tenth the size of the females, some smaller than one inch. Males have no glowing rod to attract other fish as food, but they feature larger eyes in relation to their body size and a larger scent organ than female anglers. Research suggests the eyes are used to find the female's lure and the heightened sense of smell aids in detecting sexual pheromones.

    Sexual Maturity

    • Male anglers reach sexual maturity much faster than females, often right after achieving adulthood. This stage also sees the digestive system of the male shut down. Unable to feed on his own, the male angler spends all of his time searching for a sexually mature female. Some studies suggest there are as many as 15 to 20 mature males to every one mature female.

    Reproduction

    • When a male finds a female angler, he latches onto her skin with his teeth. He excretes an enzyme that disintegrates the skin of his mouth and the skin of the female, so that they become one. The blood systems of the two fish eventually fuse together and the male gains all of his necessary nutrition from what the female eats. Over time, the male's eyes and internal organs deteriorate with the exception of the testicles. Six or more males may attach to the same female host. The female is now essentially a hermaphrodite that can fertilize her eggs at any time, controlling the release of the sperm. The fertilized eggs are buoyant and float to the surface of the ocean as a long, thin sheet. When the larvae emerge from the eggs, the spawn feed off of plankton at the surface of the water. The fish return to the depths of the sea as they mature.