We have studied the embryonic heart in the gastropod Achatina fulica using eggs soon after their deposition. We also followed the development of organs, with the main emphasis on the heart and its physiology. The embryos were examined at different stages by carefully removing egg shell until hatching. In this context the heart rate (HR) was analysed in embryonic snails and compared with that of young (from hatching) and adults. The HR of embryos dissected from newly deposited eggs was irregular, with a mean frequency of 0.42 +/- 0.14 Hz. The heartbeat during the ontogeny was more rhythmic and HR increased to 0.82 +/- 0.12 Hz. The intersystolic intervals (ISI) in real time showed a Gaussian distribution for all animals. The peak ISI from Gaussian fit closely matched the cumulative probability for corresponding data. Although the HR increased after hatching, comparisons yield a weak correlation (R = 0.56 +/- 0.27) with the total body weight of embryonic, young and adult snails.
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