Comparison of two kinds of functional asymmetry in the roach Rutilus rutilus (Teleostei: Cyprinidae)
374 Cartilaginous epicoracoid plates in the arcipheral pectoral girdle of modern amphibians intersect ventrally along the body midline and overlap so that either the right or the left plate is located dorsal to the other [1, 2]. The ratio between the left and right variants in amphibian populations is species-specific; in different species, the left epicoracoid is in the dorsal position 3– 20 times more often than the right one [3–6]. There is a hypothesis  that the asymmetric structure of the shoulder girdle is determined by the difference in the muscle tone between the sides of the body, which is, in turn, related to the functional asymmetry of the nervous system: differences in muscle tone lead to the shift of one epicoracoid away from the midline. Indeed, there is an association between the directions of the asymmetry of the shoulder girdle and the lateralization of the use of forelimbs by Bombina bombina in the snout-wiping test . On the other hand, no significant correlation between the shoulder girdle asymmetry and preferential use of the right or left forelimb in the underwater righting test has been found in Bufo marinus . We believe that this discrepancy between the results of the two tests appears because the asymmetric structure of the girdle affects the results of a more difficult test (performed by a semiaquatic toad species outside the water), but not the results of an easier test (performed by a terrestrial toad species underwater) .