The environmental physiology of Bufo bufo L. and Bufo calamita Laur. tadpoles.

Using spawn collected from the north Merseyside sand dune system, the effects of temperature on growth, development, metabolism and metamorphosis in B. bufo and B. calamita tadpoles were investigated, together with a limited study on the effects of L-thyroxine. The effects of density on growth, developteI1t and metamorphosis were examined. Physiological and behavioural effects of B. bufo tadpoles on B. calamita tadpoles were also studied. B. calamita spawn and tadpoles survive at higher temperatures than B. bufo. Below20°CB. bufo spawn, and below 15°Ctheir t.adpcl.es, develop at a greater rate than B. calamita. B. calamita spawn and tadpoles' growth and development is faster at higher temperatures. B. calamita tadpoles have higher metabolic rates than B. bufo across the temperature range 15-30°C. Faster rates of metabolism and development in B. calamita result in smaller tadpoles and toadlets than B. bufo. B. calamita may compensate for this with increased metamorphic efficiency in terms of energy. It is speculated that differences in tadpole thyroid physiology could account for observed differences. metamorphic efficiency was greatest, and rates of development and growth maximised/at the tadpoles' preferred body temperature. Increased density reduced growth-and developteI1t of tadpoles, but influenced different stages in the two species. metamorphosis in all B. bufo tadpoles was delayed, whereas in B. calamita a proportion of the population metamorphosed apparently unaffected by increased density. The responses of tadpoles to temperature and density were related to the species' preferred spawning environments. In the presence of B. bufo tadpoles, B. calamita growth, development and metabolism was suppressed. The pattern of development and timing of metamorphosis in B. calamita became similar to that of B. bufo. Inhibition was not relieved by L-thyroxine, and did not effect tadpole behaviour. Mass specific food consumption was increased. It is speculated that the inhibitor is a parasite or a substance which affects assimilation.