ABSTRACT
Some new urodele intergeneric hybrids were obtained by artificial fertilization in vitro.
Hybrids of Pleurodeles waltlii ♀ × Euproctus asper ♂ do not generally survive beyond the late blastula stage. They show a disorderly hyperactivity of the sperm asters and of all asters for as long as they five. This hyperactivity causes aberrant cell division and complex aneuploidies which are the direct cause of death. It has not been shown that balanced diploid nuclei of this hybrid could not support further development.
The combination P. waltlii ♀ × Triturus helveticus ♂ is lethal, the hybrids do not normally gastrulate. The sperm shows a lytic activity which disturbs the yolk and ribonucleoprotein gradients of the egg.
The combination P. waltlii ♀ × Ambystoma mexicanum ♂ dies soonest. The sperm shows extreme toxicity to the egg cytoplasm. The first cleavage spindle is not formed and cleavage does not occur.
Hybrids from the cross P. waltlii ♂ × Salamandra salamandra ♂ often succeed in gastrulating and may reach the equivalent of a tail-bud stage. Chromosomal anomalies, notably elimination leading to aneuploidy, are seen from the onset of development. Cases of polyploidy and gynogenesis were seen.
In the two crosses P. waltlii ♀ × E. asper ♂ and P. waltlii ♀ × S. salamandra ♂ it was found that RNA accumulates in the male pronuclei.
