Angler fish | Nature Adventure

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Biology

Anglerfish are carnivorous fish with a unique adaptation for hunting their prey. They have a lure on their foreheads that they shake to draw in curious fish. The shape of this lure differs from species to species; sometimes its in the shape of a worm or other bit of food, sometimes its a bioluminecent organ that produces a mesmerizing glow in the darkness. Several types of anglerfish live in areas of the ocean that still receive sunlight, but the most abundant kinds live in the deep ocean, where light doesn't reach!

Photo by the Monterey Bay Aquarium

For an anglerfish to glow, it must first acquire a store of luminous bacteria. Each species uses its own unique kind of bacteria, which have evolved to share a symbiotic relationship with the anglerfish. Since these bacteria are so specialized to their host species, it's theorized that the bacteria may be transferred directly to developing eggs during the fertilization process. Otherwise, they would have to be picked up in the ambient seawater; a difficult thing to accomplish in the deep, dark sea, but also a possibility! While scientists are still unsure how exactly this relationship starts, it's vital to the survival of both the bacteria and the anglerfish!

In addition to their lures, anglerfish have extremely wide mouths and rows of backwards-facing teeth. They are ambush predators, lying in wait for a fish to swim close enough to catch. In the deep sea, food is rare. Moving too much costs energy that the anglerfish can't afford to waste! But when there is an abundance of prey, the anglerfish's stomach can extend, allowing it to eat fish twice their size!

Ecological Importance

The full extent of what anglerfish do for the ocean ecosystem isn't fully known - and that's because most of these fish live in the mysterious deep sea, in a zone that we simply haven't explored too much of! We know that they are predators, using their lures to attract prey, and we know so much about their unique lifecycles; but the vast, open ocean in these deep sea zones is still an area where many discoveries can be made. Modern technology has only recently enabled us to travel to these depths on a more reliable basis!

The unique ecological structure of the deep sea is something that marine biologists are still piecing together. How life works at this extremely intense environment, devoid of light and under several hundred times more pressure than normal gravity exerts on us, may as well be like figuring out a different planet's ecosystem!

The world is vast, beautiful, and still full of unknowns. These fish are just some of the many bizarre creatures out there, some of which have yet to be seen at all! Who knows what else might lie at the bottom of the ocean?

Did you know?

The iconic anglerfish you see in photos and movies are almost always female!

The males are never really talked about much, and there's a reason for that - they aren't much to look at! In most species of anglerfish, males are much, much smaller than the females. They're essentially only a mouth and some reproductive organs. His only goal is to find a female and attach himself to her by biting her body and fusing his face away, essentially gluing the rest of his body to her. He survives this, but only as an almost-parasitic organism. The female anglerfish can then choose when to use the male's sperm to fertilize her eggs, and may have more than one potential mate fused to her at a time.

This intense degree of sexual dimorphism, when there are notable differences between males and females in the same species, isn't present in every type of anglerfish - sometimes the males and females are the same size, and males live perfectly normal lives without having to fuse their bodies to their mates. But for the species most people think about when they picture an anglerfish, they're thinking of the females!

Photo by Peter David, Getty Images

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