Giant nuclei formation in the yolk sac syncytium of the muskellunge, a bony fish (salmoniformes: esocidae: Esox masquinongy).

In muskellunge blastulae the yolk sac syncytium originally contains nuclei comparable in size to the blastomere nuclei from which the syncytial nuclei arose. By mitosis the originally diploid syncytial nuclei become numerous and crowded together. Continued synchronous mitosis of neighboring syncytial nuclei and the resultant crowding together of their spindles culminates in overlapping spindles, multipolar spindles, disorganized spindles, and the crowding together of large numbers of condensed chromosomes from contigous spindles. When such an aggregation of condensed chromosomes becomes enclosed within one nuclear membrane, a giant nucleus appears in the following interphase. It soon becomes postmitotic.