Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 52. (Budapest 1960)

Berinkey, L.: Further morphological and osteological investigations on the hybrids of Hungarian Cyprinids

The crista of the supraoccipitale is low in the bleak, but highly protuberant in the rudd ; that of the hybrid is small, completely of a bleak character. The hollow on the ventral side of the basioccipitale (serving for the inclusion of a pad used in the mincing of the food) is posteriorly the broadest in the bleak, narrowing in an inward arch medially, to broaden again on its posterior end ; the posterior process of the bone is narrow. In the rudd, the hollow is the broadest medially, narrowing almost evenly in either directions. This bone of the hybrid must be regarded as bleak-like, since it differs hardly visibly from it. The palatinum of the hybrid agrees completely with the same bone of the bleak. The hyomandibulare of the bleak is elongated, narrow, its posterior edge straight. In the rudd, the hyomandibulare is relatively short and broad, its posterior margin of a concave arch ; the bone of the hybrid agrees with that of the rudd. The greatest breadth in the length of the hyomandibulare is 28,2% in the bleak, 43,5% in the rudd, and 44% in the hybrid. The glossohyale of the bleak is arched dorsoventrally, its anterior end never broadening (wholly cylindrical) ; while in the rudd this bone is straight, its anterior end flattening and broadening. The bone of the hybrid agrees with that of the rudd. The anterodorsal edge of the dentale is broad in the bleak, the posteroventral margin of the bone is also broad and it curves strongly downwards, while, in the rudd, both edges of the bone are narrow and the posteroventral margin curves inward. The rudd character dominates on this bone of the hybrid. The caudal process of the quadratum is long and narrow in the bleak, but short and thick in the rudd. In the rudd, there is an oval opening, orally and directly behind the condylus, a feature missing in the bleak. The hybrid conforms wholly with the rudd. The opercula of both parent-species is rather similar to each other, the main difference being that the operculum of the rudd arises more abruptly posteroventrally than that of the bleak, the smallest height in the greatest height being 52,8% in the rudd, 65% in the bleak, and 57% in the hybrid. Concerning this bone therefore, the hybrid displays a transitional form between the two. The lower branch of the preoperculum is relatively longer in the bleak than in the rudd, the length of the lower branch in that of the upper branch being 83,2% in the bleak, 68,6% in the rudd, and 76,7% in the hybrid. We have also here a transition, showing the effects of both parental species. Fig. 1—3. Vomer. — Fig. 1. Scardinius erythrophthalmus ; fig. 2. Alburnus alburnus ; fig. 3. Hybrid.