EWOLUCJA ŻYWORODNOŚCI WŚRÓD RYB
Fishes shown enormous variety of reproduction modes. Viviparity evolved independently in several groups of chondrychthyan and osteichthyan fishes. Both maternal and embryonic adaptations for viviparity are extremely diverse and involve maternal reproductive organs (oviduct, uterus, internal ovarian epithelium and follicle) and specialization of embryonic tissuesbody surface epithelium, buccal epithelium, gill and gut epithelium for gas exchange and nutrient transport. Multiple origin of adaptations for viviparity in fishes may be one of the best examples of evolutionary plasticity in vertebrates.