| clutch effects explain heart rate variation in embryonic frogs (cave coqui, eleutherodactylus cooki). | few physiological studies to date have focused on whether variation among sibling groups during development can account for often large, intraspecific physiological variation. in this study, we measured heart rate in the direct-developing frog eleutherodactylus cooki throughout its embryonic development and examined heart rate variation among egg clutches comprising from 10 to 40 eggs. clutches were collected in the wild in yubucoa, puerto rico, and individual eggs were maintained under equivale ... | 2006 | 14671715 |