Veggie Delight, Eco Disaster
A favorite food of rural Zambians, a meatless sausage called chikanda—or “Zambian bologna”—has become a popular snack in urban markets in Zambia and South Africa. Chikanda is made by cooking the ground tubers of wild orchids with peanut powder and spices, making a paste that thickens to a sliceable patty as it cools. Rural Zambians eat chikanda with nshima, a corn-or rice-based meal that is the staple food of the region, while urbanites eat it as a sandwich.
The Wildlife Conservation Society has brought attention to the illegal trade of the wild orchid tubers used in chikanda. In a recently released report, Tim Davenport, a conservation biologist at WCS, and Henry Ndangalasi, a botanist from the University of Dar es Salaam, say that up to 85 species of orchids are being strip-mined by the millions from the southern highlands of Tanzania each year. Tanzanians are eating fewer tubers themselves, as chikanda has declined in popularity there, so the plants are intensely harvested strictly for export.
Truckloads of orchids cross into Zambia each day in violation of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which protects endangered wildlife through regulation of international trade. According to the WCS report, people of all ages, including young children, participate in harvesting orchids for supplemental income. As the orchids are removed from the hillsides and grasslands where they were once found, people are having to travel much greater distances to reach good collecting sites.
Davenport estimates that many species of wild orchid—some of which are endemic to the region—will be eliminated within a few years. To help protect the biodiversity of the largely unexplored region of Tanzania, WCS is working to establish a national park in the Kitulo Plateau, an important sector of the southern highlands. Moreover, the attention WCS has focused on the export of such valuable resources should result in tighter enforcement of CITES rules.
BETTER COMMUNICATING THROUGH CHEMISTRY
Long before telephones, telegraphs, sema phores, and smoke signals, there was long-distance communication. Alarm signals and come-hither messages intended for very specific recipients have been floating through air and water for ages. However, scientists have only recently begun deciphering the plethora of messages and their meanings.
The chemical messages traveling between individuals of the same species are known as pheromones. Initially discovered and best understood in insects, pheromones have been found to be operating in most vertebrates as well. The attraction to studying pheromones is obvious: The variety of chemical signals used and the potency of the responses they elicit, often at very low concentrations and over long distances, are compelling. And because reproduction is often tied to these little love chemicals, there is also the possibility of controlling insect populations, particularly pest species, by manipulating their behavior with pheromones.
Mammals, like many other vertebrates, have two olfactory systems, which until recently were thought to operate separately. The olfactory epithelium, lining the nose, primarily detects odorants and sends signals to the cerebral cortex (which is how we are conscious of smells). The accessory olfactory system, called the vomeronasal organ, picks up pheromones and sends signals along a different neural pathway, straight to the midbrain, where they elicit physiological and behavioral responses. However, scientists from Harvard Medical School and Indiana University report (Nature 412: 142) that the vomeronasal organ in mice detects odorants as well as pheromones. When bathed in individual odorants or mixes of odorants labeled “musky,” “fruity,” “floral,” and “woody,” vomeronasal neurons reacted to more than one odorant or mix and distinguished between closely related compounds, at concentrations below the level required for an olfactory neuron to fire.
“This suggests that in mammals, as in insects, odorous compounds released from plants or other animal species may act as ‘semiochemicals’—signaling molecules that elicit behaviors that are advantageous to the sender or the receiver,” said Milos Novotny, director of Indiana University's Institute for Pheromone Research. By directly telegraphing parts of the midbrain controlling instinctive behaviors and hormonal reactions, what messages do these odor molecules convey? Perhaps the basis for instinctive behavior is just such a tightly tied response to environmental cues indicating danger, say, or a particularly favorable habitat, using the same system animals use to signal each other with pheromones.