Dogged by hyenas
The dog-eat-dog world of the wild, not just human interference, may be contributing significantly to the demise of the African wild dog. The critically endangered species, with only about 5 000 animals remaining in the wild, may be succumbing not just to loss of habitat but also to thievery by spotted hyenas, who steal food the wild dogs work so hard to capture. Zoologists at the Kruger National Park have calculated that if a wild dog lost just a quarter of its day’s catch, the animal would need to hunt more than 12 hours a day to make up for the stolen calories. Such an enormous increase in hunting time would be physiologically untenable. The researchers based their conclusions on measurements of the wild dog’s metabolic rate at rest and calculations of the rate for hunting.
In a report in the journal Nature, the scientists suggest that if the wild dog is to be rescued in the wild, efforts should be concentrated in places where hyenas are relatively rare and in areas of thick vegetation where hyenas would have a harder time detecting kills by wild dogs.
Mind over matter
Some bodybuilders appear to be suffering from an emotional disorder that, despite their muscular bodies and tiptop shape, convinces them that they look puny. This makes them spend hours at the gym “bulking up”. Case studies of the disorder, called muscle dysmorphia, were described in the journal Psychosomatics for the first time. Researchers think the underlying cause of the condition may be the same as anorexia, because both involve distortions of body image.
Said one: “Muscle dysmorphia may become the body-image disorder of the 1990s, much in the way that eating disorders leapt into public awareness in the 1980s.” Many of those studied had taken anabolic steroids or other body-building drugs to enhance their muscular development. Most weighed themselves several times a day, repeatedly examined their bodies in mirrors and wore baggy clothes to conceal their “puny” bodies.
Oriental ancestors
New fossil discoveries in China have transported palaeontologists across a great divide in the history of life on Earth, showing them the earliest known forms of tiny ancestral animals. Two teams of palaeontologists have found minute but distinct traces of ancient marine animals and embryos exquisitely preserved in phosphate deposits. The specimens are related to sponges, jellyfish and even more advanced species, including apparent forerunners of trilobites, clams and crabs.
Under a magnifying glass, the tiny mineralised organisms reveal striking details down to the cellular level, establishing the abundance and diversity of ancestors of today’s animals at least 570- million to 580-million years ago. This extends the fossil history of animals back at least 30-million to 40-million years before the Cambrian explosion, the great evolutionary divide when it seemed that complex life suddenly appeared in a burst of anatomical innovation sometimes called the “big bang of biology”.
The discovery of such early fossil organisms, which are more complex than sponges or jellyfish, leads scientists to suspect that the initial appearance of multi-cellular animal life must have occurred at a much earlier time. Specialist in evolution studies Stephen Jay Gould notes: “A whole new world of small-bodied organisms is now open for discovery. That, to me, is the greatest significance of this achievement.” The last comparable step, Gould recalls, occurred in 1953.