Thursday, July 7, 2011

When two become one (for real)

The deep sea anglerfishes of my previous post are famous for their strange reproductive habits. These habits are strange because they are much more similar to the feeding habits of most other organisms. In the early 1900's, biologists started finding female deep sea anglerfishes with tiny fish attached by their snouts to the females' bellies. Sounds like those poor ladies were getting eaten, right?

Nope, it turns out that those tiny fish were the men in their lives. When I say tiny, I mean that in the most extreme species, the females can be more than 60 times the length and about a half a million times as heavy as the males. These males look nothing like the intimidating females--the anglerfishes you're thinking about, with large jaws and lures for catching prey. The males have neither large jaws nor lures: the only thing large about them is their nostrils, which helps them to find a female in the dark depths of the sea. In some species, once the male finds a female, he attaches permanently to her, becoming embedded in her mass. Their tissues fuse together, and even their blood circulates together. He becomes completely dependent upon her for nutrition, living effectively as a parasite, waiting to provide sperm when she decides to spawn. In some species, the females take on just one male, but in others, females can absorb up to eight.

Unfortunately I don't have any photos to post***, but in reading up about this I stumbled upon some historical quotes that are too good not to share.

This quote is from C.Tate Regan, who, in 1925 was the first to conclude that the tiny fish attached to the females must be males. He romanticizes the phenomenon to the point that it almost, perhaps, maybe, possibly, sounds ... beautiful? If anyone needs an eccentric quote for a toast at an upcoming biologist's wedding, here ya go:
[The male fish is] "merely an appendage of the female, and entirely dependent on her for nutrition, ... so perfect and complete is the union of husband and wife that one may almost be sure that their genital glands ripen simultaneously, and it is perhaps not too fanciful to think that the female may possibly be able to control the seminal discharge of the male and to ensure that it takes place at the right time for fertilization of her eggs."
Then there is this quote, from William Beebe, writing in 1938. He, on the other hand, makes the phenomenon sound, well, utterly terrifying:
"But to be driven by impelling odor headlong upon a mate so gigantic, in such immense and forbidding darkness, and willfully to eat a hole in her soft side, to feel the gradually increasing transfusion of her blood through one's veins, to lose everything that marked one as other than a worm, to become a brainless, senseless thing that was a fish--this is sheer fiction, beyond all belief unless we have seen the proof of it."
 And proof of it, indeed, he--and many others--have seen.

*** We do have a female specimen with a parasitic male attached, but it's been used for teaching so much that it's in danger of falling off, so I didn't want to risk making it worse by taking it out to photograph it. Sigh...


Sources:

Pietsch, Theodore W. 1976. Dimorphism, Parasitism and Sex: Reproductive Strategies among Deepsea Ceratioid Anglerfishes. Copeia, No. 4, pp. 781-793.

Pietsch, Theodore W. Ceratioidei. Tree of Life Web Project.

Pietsch, Theodore W. 2009. Oceanic Anglerfishes: Extraordinary Diversity in the Deep Sea. Berkeley and Los Angeles, University of California Press.

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