Letters To The Editor

At the end of his review "Meat and Right" (June 1999), Steven Austad asks what kind of egotist it takes to break a 5-million-year-old tradition of killing and eating other animals. A more interesting question might be, What kind of egotist defends his own patterns of consumption despite growing awareness of the harm they may be doing the planet? We know the threat to global climate caused by the sacrifice of rainforests for short-term meat production. We are aware of the huge environmental problems created by the waste products of animals on factory farms. We hear of biological and bacteriological hazards engendered by the use of antibiotics and hormones in animals. We face ethical issues surrounding cloning and genetic manipulation. We know that numerous animal species, already threatened, are further endangered by hungry poachers. We know that our oceans are becoming empty. We also know the amount of usable protein produced by an acre of soybeans compared with that of an acre devoted to pastureland.

We may have hunting to thank for aspects of our species' early development, but today our relationship to our planet requires a rethinking of basics.

Julian Jackson Brooklyn, New York

Oxygen Dependence

I believe Louise Hose, in "Cave of the Sulfur Eaters" (April 1999), overstates the case by saying that the Villa Luz cave ecosystem depends for energy "not on photosynthesis from sunlight but on an inorganic chemical process." To oxidize sulfur, the cave bacteria need atmospheric oxygen--all of which is manufactured by photosynthesis. Only anaerobic organisms are truly independent of this process.

Parallels cannot then be drawn between a sulfur-based cave ecosystem and possible subsurface life on Mars.

John H. McClendon via E-mail

LOUISE HOSE REPLIES: John McClendon correctly notes that Cueva de Villa Luz is an aerobic system and thus not a perfect analogue for the study of possible Martian biota. But even aerobic microorganisms create atypical microhabitats that may throw light on potential extraterrestrial biospheres. Exobiologist and Villa Luz researcher Penelope Boston points out, for instance, that some Villa Luz cave organisms use nitrates rather than molecular oxygen as ultimate electron acceptors and that nitrates have long been suspected to be present on Mars.

In addition, many of the cave microorganisms that we are studying are anaerobic. Boston hypothesizes "an anaerobic subsurface biosphere that depends neither on photosynthesis nor on oxygen respiration but on reduced gases flowing upward from the interior." She adds that "because of our complete lack of knowledge of the Martian subsurface, we cannot rule out the presence of oxygen or oxidized materials there."

A Cereus Mistake

In "Life in Bloom" (May 1999), the photographs of night-blooming cereus were upside down and in the wrong sequence. Cereus blooms hang from their stalks, which begin to curve as the full bloom approaches. At its greatest expansion, the blossom provides a visiting bat with a suitable landing platform. If a bat were to approach the flower as it was shown in your photo, it would make contact only with the anthers, not with the protruding, multibranched stigmas, and thereby fail to pollinate this fascinating creation.

Robert D. Bergad White Bear Lake, Minnesota

Several readers pointed out our mistake. The corrected sequence, right side up, is reprinted below. --Editors

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