Presporogonic development of Sphaerospora renicola Dyková & Lorn, 1982, in the swimbladder of the common carp, Cyprinus carpio L.

The prcsporogonic developmental stages of Sphaerospora renicola, the causative agent of swimbladder inflammation (SBI), develop in the swimbladder of common carp by multiple internal cleavage. The earliest development stage is the secondary cell enclosed by the primary cell. The secondary cells undergo multiple amitotic division within the mother cell and the dividing forms are connected by narrow cytoplasmic bridges. As a result of further internal cleavage, two tertiary cells appear in each secondary cell. The triple formation enclosing a secondary and two tertiary cells is identical with the pansporoblast containing two sporoblasts which occurs in the renal tubules.