A mechanism for diversity in warning signals: conspicuousness versus toxicity in poison frogs.
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Many animals advertise their chemical defense to predators with conspicuous coloration and unpalatability, but little is known about the information in these signal elements. To effectively avoid predation, is it more advantageous to invest in increased conspicuousness or greater noxiousness, or to allocate equally to both signal modalities? Using natural variation among poison frog species measured with spectral reflectance and toxicity assays, we tested the relative importance of warning signal components with predator-learning and avoidance experiments. We demonstrate that closely related species use alternative strategies: increasing either conspicuousness or toxicity affords equivalent avoidance by predators and provides protection to nontoxic mimic species. These equally effective predator avoidance tactics demonstrate different aposematic solutions for two potentially costly signal components, providing a mechanism for natural diversity in warning signals. (+info)
A novel conotoxin, qc16a, with a unique cysteine framework and folding.
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A retrospective study was done of poisonous snakebite in Utah to determine the current epidemiology and scope of treatment, reviewing emergency department logs and other sources statewide for a 69-month period. Of 61 cases of poisonous snakebite identified, 13 occurred in snake hobbyists or venom laboratory personnel and were considered nonaccidental, and 48 were inflicted by native noncaptive snakes. These bites were considered accidental, and all were presumed to be from rattlesnakes. Nearly three fourths of the victims were male, ranging in age from 2 to 56 years (mean, 22 years). Most accidental bites occurred in areas of high human populations, during the summer months, in the afternoon or evening hours, and during recreational activities. Of the 48 bites, 11 (23%) were provoked. Two thirds of bites were on the upper extremities, and a third were on the lower extremities. More than half of the victims had no first-aid treatment recorded. Of those who did receive first aid, many were subjected to possibly harmful treatments, including tourniquets and ice application. The median time to a hospital was 68 minutes, with a range of 15 to 440 minutes. Swelling and discoloration were the most common signs and pain and paresthesia the most common symptoms. Half the bites resulted in minimal or no envenomation, 17 (35%) produced moderate envenomation, and 6 (12%) severe envenomation. Most patients with moderate or severe envenomation received antivenin, but the dosages given were usually less than recommended dosages. Five patients received surgical treatment based on clinical findings. One child died in a snake-handling incident. Long-term morbidity was unknown due to lack of follow-up. The Utah Poison Control Center was poorly utilized as a reporting and informational resource. (+info)