Although limb development has been a subject of intense research over the last decades, development of the girdles has been poorly investigated. Particularly, a detailed analysis of pelvic girdle development including functional data is not available to date. Here, we describe the early steps of the formation of mesenchymal and cartilaginous anlagen of the pelvic elements using alcian blue staining in whole mount embryos and serial histological sections, and the expression pattern of several marker genes to provide an operative basis for further research in pelvis development. Moreover, we describe pelvis development after unilateral hindlimb bud amputation and somatopleural ectoderm extirpation. We show for the first time, that ectodermal signals at pre-limb bud stages are required for pelvis formation. We present evidence suggesting that the regulation of ilium development is different from the development of ischium and pubis.

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All living organisms and many of their parts are organised in an essentially similar manner: they are closed cavitary bodies consisting of 1) the inner mass and 2) a relatively thin sheath enclosing it. This organisation allows living bodies to change shape by employing hydrostatic forces. These forces are generally recognised to govern changes of shape in walled cells. To explain transformations of other organisms, other factors are usually sought. In this paper, the hydrostatic mechanism is represented as a universal mode of shape formation. It acts in all kinds of organisms, determining the course of diverse processes such as development of cell outgrowths, limb buds, gut derivatives and sense organs; endocytosis; cell division; branching of capillaries; gastrulation; cell locomotion; muscle contraction etc.

The fire-bellies are among anurans that have the minimal ratio of the number of specimens with the left epicoracoid in the top position to the number of specimens with the right epicoracoid in the top position (L.top/R.top). In Bombina there are no significant geographical and interspecies differences in L.top/R.top, whereas significant sex differences of this index were found in B. bombina. Observations on the tadpoles of the latter supported the idea that the order of limb eruption does not affect the mode of mutual arrangement of contralateral epicoracoids.

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