This paper describes a modification of the Simons and Van Horn (1971) procedure for rendering cartilage blue, bone red, and soft tissue translucent or transparent in whole vertebrate specimens. Alcian blue and alizarin red S are used to stain cartilage and bone respectively. In our procedure formalin is used as a fixative. This is a significant modification because formalin is the common fixative for museum specimens. This clearing and staining procedure is thus readily applicable to comparative studies in anatomy, embryology and systematic zoology.

Laboratory experiments, using the garter snake Thamnophis sirtalis as predator and the chorus frog Pseudacris triseriata as prey, show that metamorphosing anurans are captured more frequently by T. sirtalis than either premetamorphic tadpoles or postmetamorphic frogs. Stomach contents of wild-caught Thamnophis have similarly revealed more anuran prey in transformation than at earlier or later stages. The high susceptibility of transforming Pseudacris to snake predation appears to be a direct consequence of a body form not conducive to effective locomotion.The sustained swimming ability of premetamorphic and metamorphic P. triseriata was examined in the laboratory. It was found that until the eruption of the forelimbs, the larger a tadpole is, the longer it can maintain its position in a steady current. The length of the tail appears to be a positive factor in sustained swimming. Large hindlimbs do not appear to assist swimming and may increase drag. Tadpoles that have begun to metamorphose (forelimbs visible) demonstrate a greatly diminished ability to hold their position in a current.The maximum jumping distance of metamorphic and postmetamorphic P. triseriata was also examined in the laboratory. Individuals which have just begun to metamorphose cannot hop as far as individuals which have advanced through metamorphosis and lost their tails. Amputation of the tails from early metamorphic individuals demonstrates the retarding role that the tail has on saltatory locomotion. Additional features, such as maturation of the anterior appendages, may also account for an increased jumping ability observed in P. triseriata as they progress through metamorphosis.Anurans spend a disproportionately short time in metamorphic transformation. The rapidity of this transformation appears to be an adaptation minimizing the amount of time anurans spend in this most vulnerable form.

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Anuran reproduction is influenced by various biotic and abiotic factors, of which temperature and rainfall are the best studied. Here we examine the relationship between multiple abiotic environmental variables - specifically, air and water temperature, rainfall, barometric pressure, relative humidity and wind velocity - and the calling activity of five species (Rana sylvatica, Pseudacris crucifer, Bufo americanus, Rana clamitans, and Rana catesbeiana) in an anuran community in New Brunswick, Canada. Acoustical and environmental data were sampled hourly for 4 months during the breeding season in 1997. Logistic regression analyses indicated that each species responded to a unique combination of meteorological variables, even when calling concurrently. Calling in the spring breeding species, R. sylvatica, P. crucifer, and B. americanus, was most associated with the time of day (i.e., they called primarily at night), while calling in the summer breeding species, R. clamitans and R. catesbeiana, was associated primarily with high water temperature. Species with short breeding periods (i.e., explosive breeders; R. sylvatica, B. americanus) responded to fewer environmental variables than did species with prolonged breeding periods (P. crucifer, R. clamitans, R. catesbeiana). Prolonged breeding species responded differently to climatic variables throughout the breeding season: during the latter half of their calling periods, the time of day and a variable that predicts rain, i.e., barometric pressure, became more important, and water temperature became less important.

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