Abstract
Summary
Intact hearts of adult male toads(Bufo fowleri), collected locally in May and June (“summer toads”); gave linear heart rate-temperature relationships in the range 14-35°C. Toads from the same collection, tested in December and January (“winter toads”), also gave linear heart rate-temperature relationships, but only between 14 and 23°C. At temperatures between 23 and 35°C the heart rates of the winter toads did not increase when their body temperatures were increased. Seasonal differences in heart rate-temperature relationships had been reported for excised frog hearts and shown to be linked to seasonal changes in thyroid and anterior pituitary activities. The similar seasonal differences in heart rate-temperature relationships shown here in intact toads may also reflect endocrine changes. This working hypothesis remains to be tested directly.
Get full access to this article
View all access options for this article.
