Hen’s Teeth and Horse’s Toes Read Free Page B

male’s testis (B), has become enlarged. REPRINTED FROM NATURAL HISTORY .
    In 1922, B. Saemundsson, an Icelandic fisheries biologist, dredged a female Ceratias holbolli , 26.16 inches in length. To his surprise, he found two small anglerfish, only 2.03 and 2.10 inches long, attached to the female’s skin. He assumed, naturally, that they were juveniles, but he was puzzled by their degenerate form: “At first sight,” he wrote, “I thought these young ones were pieces of skin torn off and loose.” Another oddity puzzled him even more: these small fish were so firmly attached that their lips had grown together about a wad of female tissue projecting well into their mouths and down their throats. Saemundsson could find no other language for his description but an obviously inappropriate mammalian analogy: “The lips are grown together and are attached to a soft papilla or ‘teat’ protruding, so far as I can see, from the belly of the mother.”
    Three years later, the great British ichthyologist C. Tate Regan, then keeper of fishes and later boss of the British Museum (Natural History), solved Saemundsson’s dilemma. The “young ones” were not juveniles, but permanently attached, sexually mature dwarf males. As Regan studied the details of attachment between male and female, he discovered the astounding fact that has ever since been celebrated as one of the greatest oddities in natural history: “At the junction of the male and the female fish there is a complete blending…their vascular systems are continuous.” In other words, the male has ceased to function as an independent organism. It no longer feeds, for its mouth is fused with the female’s outer skin. The vascular systems of male and female have united, and the tiny male is entirely dependent upon the female’s blood for nutrition. Of a second species with similar habits, Regan writes: “It is impossible to say where one fish begins and the other ends.” The male has become a sexual appendage of the female, a kind of incorporated penis. (Both popular and technical literature often refer to the fused male as a “parasite.” But I demur. Parasites live at the expense of their host. Fused males depend upon females for nutrition, but they supply in return that most precious of biological gifts—access to the next generation and a chance for evolutionary continuity.)
    The extent of male submergence has been exaggerated in most popular accounts. Although attached males surrender their vascular independence and lose or reduce a set of organs no longer needed (eyes, for example), they remain more than a simple penis. Their own hearts must still pump the blood now supplied by females, and they continue to breathe with their gills and remove wastes with their kidneys. Of one firmly attached male, Regan writes:
    The male fish, although to a great extent merely an appendage of the female, and entirely dependent on her for nutrition, yet retains a certain autonomy. He is probably capable, by movements of the tail and fins, of changing his position to some extent. He breathes, he may have functional kidneys, and he removes from the blood certain products of his own metabolism and keeps them as pigment…. But 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 the fertilization of her eggs.
    Nonetheless, however autonomous, the males have not honed themselves to Darwinian optimality, for they have evolved no mechanism for excluding other males from subsequent attachment. Several males are often embedded into a single female.
    (While criticizing the exaggeration of some popular accounts, allow me a tangential excursion to express a pet peeve. I relied upon primary, technical literature for all my