spiral cleavage


Also found in: Medical.

spiral cleavage

[′spī·rəl ′klē·vij]
(embryology)
A cleavage pattern characterized by formation of a cell mass showing spiral symmetry; occurs in mollusks.
References in periodicals archive ?
Owenia collaris embryos undergo holoblastic spiral cleavage to form a coeloblastula, which, although exceptionally hollow (again like some nemerteans), conforms to the ancestral pattern for annelids (Okada, 1970).
Evolutionary implications of the mode of D quadrant specification in coelomates with spiral cleavage.
Embryos of the acoel turbellarian Platyhelminthes exhibit a modified form of spiral cleavage in which only two macromeres form before pairs or duets of micromeres are generated beginning at the four-cell stage (Fig.
The nemerteans constitute another protostome phylum with embryos that exhibit spiral cleavage.