CHEMO-ORNITHOLOGY IN THE PERUVIAN AMAZON: THREE CASE STUDIES IN THE CHEMICAL ECOLOGY OF AVIAN-PLANT INTERACTIONS OF THE YARAPA RIVER, LORETO, PERU
O. B. HILL, D. ROSANE, A. DHONDT, D. VASQUEZ, E. RODRIGUEZ

THE USE OF FISH POISON BY THE JABIRU STORK

Recent evidence suggests that the Jabiru Stork, Mycteria jabiru, exhibit highly specialized fishing behavior, like other members of the avian order Circonidae. Several anecdotal accounts asserting the bird’s use of Hura crepitans (Euphorbiaceae) latex as a fish poison were validated chemically by confirming the toxicity of this sap in the laboratory. A positive live-fish neurotoxicity assay, combined with thin-layer chromatography (TLC) analysis, indicate that H. crepitans latex contains neurotoxic alkaloids. These preliminary results are consistent with the well-established chemotaxonomy of the Euphorbiaceae.

THE ASSOCIATION BETWEEN Nothocrax urumutum’s TOXIC BONES AND ITS DIETARY FOOD SOURCE, Malouetia Peruviana

Animals can sometimes circumvent toxic effects of poisonous food sources by sequestering, rather than digesting, the toxins. Often, these sequestered toxins can serve as defenses. The poisonous bones of the Nocturnal Curassow (Nothocrax urumutum, Cracidae) is a unique avian example of this phenomenon. The link between this bird’s toxicity and the plant genus Malouetia of the Apocynaceae family was recorded from indigenous accounts by R.E. Schultes as early as 1953. According to local sources along the Yarapa River, the bones of N. urumutum are toxic to large animals. Informants attributed the toxicity of these bones to the fruit of Malouetia peruviana, supporting the information gathered by Schultes. Because the fruit was not in season, the flowers, stems, and leaves of the plant were collected and examined for their chemistry and bioactivity. A brine shrimp assay indicated cytoxicity of the extracts. Visualization of thin-layer chromatography with Marquis and Iodaplatinate spray reagents confirmed the presence of steroidal alkaloids, which have been previously found throughout the genus and implicated as the active agents for the poison bone phenomenon.

DIETARY SELECTION OF TOXIC Phoradendron sp. BY Euphonia sp.: A DEFENSIVE MECHANISM OR A NUTRITIONAL REQUIREMENT?

Coevolution between parasitic Loranthaceae members and avian dispersal agents has been well documented throughout the tropics. One example of this is the close association between Phoradendron sp. (commonly known as mistletoe) and its Euphonia sp. dispersers. Anecdotal accounts assert the selection of young mistletoe shoots as a dietary component for the Euphonia. This suggests that this bird genus is able to digest the nutritious portion of the plant without apparent negative effects. Preliminary chemical analysis using thin-layer chromatography points to the existence of compounds unique to the leaves. The leaves and fruits, separated into seeds and pulp, of Phoradendron sp. were collected and tested for their bioactivity. Toxicity, as determined by brine shrimp assays, was greatest in the seeds, followed by pulp and leaf in descending order. Disk diffusion assays were conducted against the gram-positive bacteria Bacillus cereus, the gram-negative bacteria Pseudomonas aeruginosa, and the fungus Candida albicans. The seed extract proved to be the most biologically active, inhibiting the growth of the gram-positive bacteria B. cereus. Whether the birds sequester the toxins as chemical defenses or simply eat the young shoots because of a higher concentration of essential macronutrients is yet to be determined.