Anesthesia of tadpoles of the southern brown tree frog (Litoria ewingii) with isoeugenol (Aqui-S).

Because anesthesia of amphibian larvae is currently problematic, the aim of this study was to test if a fish anesthetic containing approximately 500 g/L isoeugenol (Aqui-S) could anesthetize tadpoles. Three concentrations of Aqui-S were tested (of commercial solution 10, 20, and 50 microl/L) with 10 tadpoles of the southern brown tree frog (Litoria ewingii) per concentration. Tadpoles were anesthetized for 15 min in water at 18-20 degrees C. Anesthetic criteria included four time points and two heart rates: time to loss of response to stimulation, loss of righting reflex, and return of spontaneous movement and of righting reflex after removal from Aqui-S, and heart rate after induction and after 15 min of anesthesia. No tadpole showed signs of irritation or excitement, no tadpole died, and all returned to normal behavior. The times for induction of anesthesia (time to loss of righting reflex) decreased significantly (P < 0.001) with increasing concentration: means of 27.5, 16.8, and 5.7 min for 10, 20, and 50 microl/L, respectively. Heart rate after 15 min of anesthesia was significantly lower (P = 0.006) for concentrations of 20 and 50 microl/L compared to 10 microl/L. At the lowest concentration (10 microl/L), anesthesia was light. Recovery times were significantly delayed (P < 0.001) for 50 microl/L, approximately double those for the lower concentrations. Spontaneous movements began at 56.9, 51.4, and 119 min for 10, 20, and 50 microl/L Aqui-S, respectively. Although Aqui-S did anesthetize tadpoles at all three concentrations, with 20 microl/L being the most suitable, additional longer-term toxicity testing is required prior to its adoption as an anesthetic agent for this species. Anesthesia, isoeugenol, Litoria ewingii, southern brown tree frog, tadpoles.

Elimination of the amphibian chytrid fungus Batrachochytrium dendrobatidis by Archey's frog Leiopelma archeyi.

Archey's frog Leiopelma archeyi is a critically endangered New Zealand endemic species. The discovery of the emerging infectious disease, chytridiomycosis, in wild populations of this frog raised concern that this disease may drive the species to extinction. Twelve wild-caught Archey's frogs naturally infected with the amphibian chytrid fungus Batrachochytrium dendrobatidis were monitored in captivity by observing clinical signs, measuring weight gain, and performing repeated PCR tests. Eight frogs were treated with topical chloramphenicol, without PCR results being available, for B. dendrobatidis at the day of entry of the frog into the trial. Eleven of the 12 frogs (92%) cleared their infection within 3 mo of capture, even though they were held at 15 degrees C and in high humidity, conditions that are ideal for the survival and propagation of B. dendrobatidis. B. dendrobatidis in the remaining frog tested positive for the fungus was eliminated after treatment with topical chloramphenicol. None of the 8 frogs exposed to chloramphenicol showed any acute adverse reactions. Archey's frog appears to have a low level of susceptibility to the clinical effects of chytridiomycosis. Individual frogs can eliminate B. dendrobatidis and Archey's frog can apparently be treated with topical chloramphenicol with no acute adverse reactions. However, the small number of specimens treated here requires that more extensive testing be done to confirm the safety of chloramphenicol. The significance of the amphibian chytrid fungus for wild populations of Archey's frog needs to be determined by a longitudinal study in an infected wild population to correlate the presence of B. dendrobatidis in individual frogs. Such a study should occur over a period of at least 3 yr with clinical assessment and monitoring of survival, growth and body condition parameters.