TOPICS

X. laevis and X. tropicalis Cleavage Rates

Author

Richard Harland

Published on SDB CoRe: Feb 13 2013

Early Embryogenesis: Cleavage
Morphogenesis: Cell Movements
Organism: Xenopus
Stage of Development: Embryo

Object Description

Time-lapse movie showing that Xenopus laevis and Xenopus tropicalis embryos cleave at the same rate despite the differences in their sizes. X. laevis embryos are much larger than X. tropicalis. This size difference extends into adulthood. While cell size correlates well with genome size, the correlation does not extend to the size of the adult. X. laevis embryos have twice the number of chromosomes as X. tropicalis (2n =36 vs. 20) and are pseudo-tetraploid instead of diploid. The cleavage patterns of the two species are nonetheless quite similar. There are three slightly lighter X. laevis (large) embryos on the right that were fertilized with X. tropicalis sperm. These species hybrids were fertilized later so their cleavages are a little behind the other embryos. The one in the top right corner of the movie is undergoing abortive cleavages. This egg was activated during fertilization, but did not get a sperm centriole thus it cannot properly cleave. X. laevis and X. tropicalis have tolerance for different temperatures, with the tropical frog tolerating a higher temperature range, so that it has the ability to develop more quickly than X. laevis at its optimal temperature. Nonetheless, as seen here, their initial cleavages occur at a similar rate when they share the same temperature.

Embryos were provided by Takuya Nakayama at the Cold Spring Harbor Xenopus course.

References

Gilbert, S.F. Developmental Biology. 6th edition. Sunderland, MA, Sinauer Associates, 2000. Early Amphibian Development. http://www.ncbi.nlm.nih.gov/books/NBK10113/.