title: [Early embryo orientation by direction of the cardinal point in natural clutches of two ranidae species inhabiting geographically distant regions].
abstract: The azimuth (the least angle with the north-south direction) of the first cleavage furrow and anteroposterior axes of neurula was measured on projections of photographs of natural clutches. The azimuth distribution of the craniocaudal axis of Rana dalmatina neurulae in clutches from southern Italy and the first cleavage furrows of R. arvalis embryos in clutches from central Russia proved identical. Both craniocaudal axes and first cleavage furrows were mostly oriented from west to east. The azimuth distribution of the craniocaudal axis of R. arvalis neurulae in clutches subjected to repeated cold shock proved to be random. The causes and mechanisms of predominant orientation of the embryos in natural clutches of frogs are discussed. We propose that magnetic sensitivity is acquired by cytoskeleton elements, most likely microtubules, during reorganization in the course of normal development or due to experimental influences.
authors.affiliation: Faculty of Biology, Moscow State University, Vorob'evy gory, Russia.
authors.forename: Iu K
authors.initials: IuK
authors.lastname: Doronin
authors.forename: B D
authors.initials: BD
authors.lastname: D'Aniello
authors.forename: O N
authors.initials: ON
authors.lastname: Slobodchikova
mesh_terms: D000818:Animals; D008027:Light; D008280:Magnetics; D011898:Ranidae / Q000196:embryology*; D013045:Species Specificity