And Females Shall Rule the Deep

anglerfish.jpg The Portsmouth Herald discusses sexual dimorphism, specifically body size, in a cheeky sort of pop press way. This is something we never do (e.g. Man Eating Sponges). One comment has me concerned that the writer doesn’t read DSN.

But in many other species, it’s the female who’s the big one. In fact, the Guinness Book of World Records has just included an entry for biggest male-female difference: the deep-sea angler fish, also known as the giant sea devil. It was named before anyone saw a male. Females can stretch to around five feet long but the males are about the size of flies. The female is about 500,000 times heavier than the male, says Ted Pietsch of the University of Washington, who’s spent years studying these deep-sea dwellers. “The males are parasitic,” Pietsch says. When a male anglerfish finds a mate, he bites her, digs in, attaches himself permanently and starts living off her blood. It’s hard to fathom how that could be good for her, but at least you can’t say the male fears intimacy.

Peter and I are big fans of the anglerfish (see links to post below). I speculated in my answer to question posted by a reader that…

1. How do different types of deep-sea life find mates in such a large and sparsely populated area? Before I address this question further, I should note that Chris notes an important idea in the question. The densities of deep-sea organisms are extremely low, at least an order of magnitude lower than shallow water, and decline exponentially with depth. Confounded with the large habitat area this makes the probability of finding a mate extremely low. Organisms can counteract this through multiple strategies…e. One of the more interesting strategies, is displayed by our friends the angler fish-Sexual Parasitism. The male, extremely small, once he finds a female attaches for life ever to become a sperm bump on the side of the female.

Anlger Fish Sex
Anlger Fish Video (not of the above!)
Spawning Grounds (is there a theme here?)

Dr. M (1729 Posts)

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, a National Science Foundation supported initiative. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web. His forthcoming book, Science of the South (, connects cultural icons of South such as pecan pie with the science behind them.