from The Century Dictionary and Cyclopedia
- Dextral, as a shell; turning or turned to the right, as the whorls of a spiral shell; dextrotropous: opposed to læotropic.
- Turning to the right hand or in a clockwise direction: said of the direction of cleavage in the eggs of certain invertebrates.
Sorry, no etymologies found.
Such a division is described as dexiotropic if the clockwise daughter cell (in animal pole view) is the closer to the animal pole; in a laeotropic division the counterclockwise cell is closer to the animal pole.
Where a transverse division places sister cells at the same level of the egg axis, they are usually numbered with reference to the chirality of the previous division: if the mother cell formed by a dexiotropic division, then the clockwise product of this cell's next division is given a superscript 2 and the counterclockwise product a superscript 1.
Division of the 2m cells occurs with a slight asynchrony matching the timing of their birth; these divisions are all equal and dexiotropic, but nearly transverse
Mitotic spindles in the quadrant founder cells are skewed clockwise, preparatory to dexiotropic division.
Within each quadrant, the dexiotropic division of 1m
(D) Fifth cleavage: the third-quartet micromeres are formed by dexiotropic division of macromeres; cells of both the first and second micromere quartets divide also dexiotropically, but with a slight delay.
Also applying to shellfish are dexiotropic and laeotropic, where the shell's spire turns to the right and left, respectively.
In the 2d clone, the six latest-born nuclei form a unique pattern consisting of three laeotropically skewed columns; as development proceeds, the lower-left nucleus in this array (2d The third quartet micromeres are formed by the dexiotropic division of the 2 M macromeres.
Wordnik is becoming a not-for-profit! Read our announcement here.