In Sum

Natural History, Feb, 2001 by Richard Milner

MONKEYING WITH MILLIPEDES

Twenty years, ago, ecologist John Robinson, of the Wildlife Conservation Society, observed puzzling behavior in a group of wedge-capped capuchin monkeys (Cebus olivaceus) in central Venezuela. Upon finding a millipede, the monkeys rubbed it all over their bodies, their eyes appeared to glaze over, and they frequently placed the arthropod in their mouth while drooling. Three or four often shared a single millipede, passing it from one to the other. Afterward the monkeys rubbed up against one another, apparently to spread the millipede's secretions. Up to ten bouts of this frenetic, ecstatic anointing could take place within a single day.

In 1988 Robinson invited his student Ximena Valderrama, now in Columbia University's anthropology department, to conduct a two-year follow-up study at his field site, Valderrama collected some of the millipedes (Orthoporus dorsovittotus) used by the monkeys and sent them to chemical ecologists Thomas Eisner and Alhuta Attygalle, of Cornell University. After "milking" the millipedes for their secretions, which are produced by glands along their sides, the chemists determined that they contained benzoquinones, which are powerful insecticides and disinfectants.

Because the monkeys anoint themselves exclusively during the rainy season, when they are vulnerable to infection by mosquito-borne botfly larvae, Valderrama and her colleagues hypothesize that the animals intentionally apply the benzoquinones as protection against biting insects and parasites. Although millipede secretions contain other toxins and even carcinogens, they appear to cause the monkeys no harm. ("Seasonal Anointment With Millipedes in a Wild Primate: A Chemical Defense Against Insects?" Journal of Chemical Ecology 26:12, 2000)

A VEGETARIAN CROCODILE Until now, the fossil record of the Last 200 years has presented a remarkably stable array of crocodiles. Several gigantic varieties appeared during the age of the dinosaurs, but these long-snouted, aquatic carnivores seem not to have undergone any radical changes over the eons. Recently, however, paleontologist Gregory Buckley, of Roosevelt University in Chicago, and his colleagues unearthed the fossil skull of a previously unknown crocodile--and it appears to have been a short-snouted vegetarian.

Simosuchus clarki, extracted from approximately 70-million-year-old rocks in Madagascar, has a short pug nose, a tall head, and nostrils that point out from the front of the face, not upward, as in typical living crocodilians. Some features of the thick skull suggest that it may have been an adept head-burrower. An adult Simosuchus would have been only about three feet long.

The most unusual feature of the new species is its multicusped teeth, which resemble those of presumed herbivorous dinosaurs such as ankylosaurs and stegosaurs. Simosuchus seems to have undergone a convergent evolution with these armored, tanklike dinosaurs. In addition to the similarities in tooth form, this species had a broad, compact body and a heavy-boned skull like those of the dinosaurs. However, its skull also shows the characteristic osteoderms, or bony plates in the skin, that distinguish crocodiles from their dinosaur relatives.

The new fossil also presents a puzzle for geologists because of its resemblance to Uruguaysuchus, an extinct crocodile from South America. Buckley and his colleagues think this suggests that Madagascar and South America may have been linked 80 million years ago, long after the young Atlantic Ocean is believed to have separated the two landmasses. ("A Pug-Nosed Crocodyliform From the Late Cretaceous of Madagascar," Nature 405, 2000)

IDENTICAL EMU TWINS A group of researchers in New Zealand has documented the first case of identical twinning in birds. S. M. Bassett, of the Ratite Research Centre at Massey University in New Zealand, and several colleagues describe two emu chicks (Dromaius novaehollandiae) hatched from the same extraordinarily large egg at an emu farm in Colyton, New Zealand. The egg was artificially incubated, and humans assisted the two female chicks to emerge from the shell. Although their combined weight on hatching was about the same as that of a single normal chick, by eighteen months of age they were near average size.

Fraternal twinning--two fertilized ova becoming trapped inside a single shell--is a rare but well-documented occurrence in some birds. As with human fraternals, the two birds are no more closely related than are ordinary siblings. A DNA analysis of the New Zealand emu hatchlings' blood showed a complete genetic match, however, indicating their formation from a single ovum that split after fertilization. ("Genetically Identical Avian Twins," Journal of Zoology 247, 1999)